Can We Save Oregon Ash Trees?

By now you’ve likely heard that identification of the dreaded emerald ash borer (EAB) has been confirmed in Washington County, Oregon. The Oregon Department of Agriculture believes that the infestation has been in that county for at least three to five years. The outlook is grim.

Of northeastern Asian origin, the EAB is a small green beetle in the Buprestidae family which feeds on members of the olive family (Oleaceae), especially ash trees (Fraxinus species). Adults feed on leaves and females lay their eggs in bark crevices. Eggs hatch in seven to ten days and larvae burrow through bark to living tissues where they feed, eventually cutting off the flow of water and nutrients, which causes a slow death. Adults emerge in one to two years and typically travel only about a half mile afterwards.

In its native range, this beetle is typically not found in high numbers and does not cause significant damage to native trees. However, outside its native range it is extremely destructive to trees indigenous to North America or Europe.

The EAB is now considered to be the most destructive forest insect to ever invade North America. First detected in Michigan in 2002, it has spread through much of the U.S. (36 states and the District of Columbia). Though harmless to people and other animals, it has proven deadly to all ash species in North America, including the native Oregon ash (Fraxinus latifolia), naturally found west of the Cascades in southern British Columbia, Washington, Oregon, and northwestern California, as well as central California and the Sierra Nevada.

Spread throughout the country has been mainly by the movement of infested firewood, logs, chips, and nursery stock. Movement of emerald ash borers and their host material has been, until recently, regulated by the USDA under a federal domestic quarantine. The quarantine for emerald ash borer was repealed in January 2021.

The Oregon ash tree is currently relatively common and is a significant component of riparian forests; it is the only native ash tree in the Pacific Northwest. It is widely used for stream restoration due to its wide and spreading root system that stabilizes soil, controls sediment, and moderates stream temperatures. Widespread loss of these beautiful, long-lived trees will affect water quality (including higher stream temperatures) and change the wildlife species composition of their ecosystems, causing harmful effects on species dependent on those ecosystems.

How to help
Learn now to identify ash trees and trees that resemble them here.

If you have ash trees or know of some, familiarize yourself with the basic signs and symptoms of emerald ash borer. Reports may be made at https://oregoninvasiveshotline.org/reports/create

Also check out this article. Robert Haight, a Forest Service researcher in St. Paul, Minn., proposes a strategic approach which involves identifying beetle-infested ash trees before they show signs of damage. “One way, he says, involves searching for woodpeckers. The emerald ash borer hides its eggs in bark crevices and tunnels deeply within trees — invisible to humans, but not to woodpeckers. They pick at the tree’s bark, searching for tasty grubs.” So please keep an eye out for our friends, the woodpeckers, foraging on Oregon ash trees.

UPDATE February 2023: The Oregon Department of Forestry has collected 900,000 Oregon ash seeds; it hopes to find trees resistant to the borer in that collection. Read about it here.

More info and brochures: https://www.oregon.gov/oda/programs/IPPM/SurveyTreatment/Pages/EmeraldAshBorer.aspx

Oregon’s Readiness and Response Plan: https://static1.squarespace.com/static/58740d57579fb3b4fa5ce66f/t/60772a17647ad466155f74a7/1618422303582/March+2021_EAB.pdf

Xerces Society: https://xerces.org/blog/how-to-spot-and-slow-emerald-ash-borers-in-your-community?fbclid=IwAR0iLt9u-DQlfETCOEUMet6F86Hmr8SWWYUIb-2-4G7PrItVfgYf7JVL-Eg


© 2022 Eileen M. Stark

Pacific Northwest Native Plant Profile: Pine (Pinus species)


Well over one hundred species of pine help support our planet, which makes the genus Pinus the largest within the conifer phylum known as Pinophyta, the woody cone-bearing plants. Found across the Northern Hemisphere, Pinus is of ancient origin, having appeared around 180 million years ago. In addition to the rich wildlife habitat, beauty, shade, fragrance, rain interception and carbon sequestration they provide, the majority of pines are drought tolerant, fire resistant and most can be extremely long-lived, with some species surviving 1,000+ years when undisturbed.

How they grow
Evergreen and resinous, pines generally grow 50–150 ft tall, although some, like ponderosa pine, can grow over 200 feet (one in southern Oregon’s Rogue River-Siskiyou National Forest towers to more than 268 feet tall!).

On adult pine trees, needle-like leaves are green and bundled in clusters called fascicles, unlike other conifers. Each fascicle can have one to seven needles, depending on the species, and assist in identification. In the Pacific Northwest west of the Cascades, there are five native pine species, a few of which can also be found at fairly high elevations east of the Cascades summit. They have either two, three, or five needles per fascicle, which stay on the plant for anywhere from two to forty years, again depending on the species.

Seed cones (female) are hard and woody, with tough scales that serve to protect the developing seeds until dispersal time comes. In some species, maturity of the cone causes scales to open and free the winged seeds. In others, scales need to be broken or pecked open by a hungry animal in order for the seeds to be released. And then there are the species that have scales sealed shut with resin: Known as “serotinous” cones, they need a trigger to release their seeds. Although serotiny can be caused in some plants by excessively moist or dry conditions, high solar heat, or death of a branch or the plant, most pines that are native to regions where wildfire naturally occurs depend on the high temperatures from periodic fire to soften the resin and expose the seeds. Fire has been a part of various natural ecosystems for millennia; having a canopy full of seeds ready to go following a fire ensures dispersal for a new generation without competition. But it can take decades for that to happen and on many sites currently, such fire regimes no longer exist. When natural fire is suppressed, species that need fire to regenerate will slowly die without ever releasing their seeds, and species dependent on those pines are consequently affected.

Pines do best in open areas and are not shade-tolerant. Generally, they don’t need rich soil and do best if it drains fairly quickly. Some can survive in harsh environments such as cold, exposed ridges at high elevations or latitudes, or even the wet and windy Pacific coast.

Wildlife value
Pines are one of the most valuable food plants for wildlife in the Pacific Northwest, particularly for small mammals like chipmunks and squirrels, as well as birds such as grosbeaks, jays, chickadees, and nuthatches who forage on the highly nutritious seeds and help distribute them. Larger birds, including woodpeckers, also use pine trees as food sources, particularly dead and dying pines. Pine needles may be eaten by some Lepidoptera (butterfly and moth) species (such as the larvae of western pine elfin that use lodgepole and ponderosa pine for food), as well as by pine sawfly, deer, and mountain goats; needles are also used in nest building. Large pines provide excellent roost and nest sites, while smaller pines offer crucial cover for many animals. Fallen needles may serve as bedding for larger mammals such as deer.

Native pines west of the Cascades
Below is info on the five native pine species that occur in the PNW west of the Cascades, plus one honorable mention; they are noted according to the number of needles per fascicle. If you want to identify a particular tree, count the needles per fascicle, evaluate the appearance of the cones, and check the natural range.

Fast-growing Pinus contorta evolved into four varieties, each of which adapted to its geography. Despite their large ecological and morphological variability, all varieties of P. contorta have two stiff, one to three-inch long needles per fascicle, which are often twisted and are mostly found toward the ends of twigs. The seed cones are small (typically one to three inches long), hard, prickled toward the top of the cone, and found near branch tips. The varieties are inter fertile in areas where their ranges overlap.

Pinus contorta var. contorta

Three varieties are found in the PNW. It was shore pine (a.k.a. beach pine or twisted pine), Pinus contorta var. contorta, that led David Douglas to offer the species’ epithet contorta when he first laid eyes on one in 1826: Reportedly, he found some relatively short trees growing in contorted and gnarly outlines near the mouth of the Columbia River on wind-swept, rocky sites with the added insult of oceanic salt spray. Bark is thick, deeply grooved, and a deep red-brown in color. Small brown cones are often asymmetrical and release seeds at maturity. Adapted to poor and rocky soils, shore pine’s range includes the San Juan islands, the outer coasts of British Columbia, Oregon, Washington and northern California, bogs of Alaska and Washington, and only occasionally the Puget-Willamette Trough. On more sheltered sites, this coastal species will grow taller and more erect (up to about 50 feet tall), and slightly resembles the appearance of Pinus contorta var. latifolia (lodgepole pine), which naturally occurs further inland, mainly in the Washington Cascades east of the Puget Trough and at higher elevations (up to 11,500 feet).

Lodgepole pine grows taller (up to ~100 feet) and more slender (especially when growing close together) with thin bark and a narrow crown. Adapted to stand-destroying fire, it is one of the first trees to come back after a natural periodic fire; its cones, which vary in shape and may be solitary or paired, are considered fire-dependent. However, this cone characteristic varies with tree age and local fire history, with older trees and those growing in areas with frequent fires able to produce serotinous cones. Remarkably, some lodgepole pine trees are even more variable, having both serotinous and nonserotinous cones, which may enable future trees to adapt to change.

Pinus contorta var. murrayana, Sierra-Cascade lodgepole pine, grows in the eastern Cascades of southern Washington, Oregon and the mountains of California. Its cones usually open on the tree when mature, before a fire. Both lodgepole pines will grow in situations that other conifers cannot tolerate.

Another tall, handsome pine is Pinus ponderosa, or ponderosa pine (aka western yellow pine), a fairly fast-growing tree to 100 feet by 25 feet in cultivation, larger in natural areas. With bundles of three long, pointed bright green needles that fall off after several years, ponderosa pine has a straight, robust trunk and a wide, open, cylindrical crown when mature. Bark is furrowed and dark on young trees; on older trees the thick, fire-resistant bark typically turns a golden brown or cinnamon color, flakes off into scaly plates separated by deep fissures, and has a vanilla scent in heat. Tan to reddish-brown, conical or egg-shaped female cones have stiff prickles that curve outward. The root system spreads widely and has a deep taproot. Although best grown in full sun with well drained, deep, somewhat moist soil when young, ponderosa pine is reportedly adaptable to a variety of elevations, soil and humidity, and is drought tolerant when established. Damage may occur due to late frosts.

Lustrous needles of Pinus ponderosa subsp. Benthamiana.

Ponderosa pine is subdivided into five subspecies; P. ponderosa subsp. ponderosa is most commonly found in cold, dry environments east of the Cascade summit, throughout the Rocky Mountains and southward. Pinus ponderosa subsp. Benthamiana (aka Pacific ponderosa) is endemic to the Willamette Valley (where it is sometimes called Willamette Valley pine or Pinus ponderosa var. willamettensis), as well as the mountains of southwestern Oregon, parts of California and a few sites in western Washington. Genetically different from ponderosa subspecies in other ecoregions, it usually has longer needles (up to nine inches) and is suited to higher rainfall in valley bottoms, as well as drier slopes. Prior to 1850, it thrived in oak savanna, riparian forest and upland prairie dispersed among other species (particularly Oregon white oak, Quercus garryana). Logged extensively by settlers as they cleared the land for lumber, agriculture and other development, until recently the only remaining native stock in the Willamette Valley survived in small scattered stands. Wildlife who needed the trees for food and nesting habitat suffered from the loss, including the rapidly dwindling Lewis’s woodpecker (now extirpated; there have been no breeding records in the Puget Lowlands since 1980; the last known nest in the Willamette Valley was near Scapoose in 1970; they have not been seen in the Rogue and Umpqua Valleys since the early 1990s). While this pine does best in full sun and moist but well-draining soil, it also tolerates somewhat dry conditions and lean soils. Choose associate species from Oregon white oak (Quercus garryana) ecosystems in this post.

Another three-needled pine that possesses similarities to ponderosa pine is Jeffrey pine, Pinus jeffreyi, named by Scottish botanist John Jeffrey. A major difference is its range: In the PNW it occurs only in southwestern Oregon at 4800 to 9600 feet in elevation, often in windswept outcroppings or on serpentine and other nutrient-poor soils where it grows slowly but outcompetes other trees. In addition, its needles are a duller bluish-gray and thicker than ponderosa pine’s, and they are typically held longer (five to eight years). Cones become much larger (up to 12 inches long), with prickles that curve inward. Older bark tends to be darker and more narrowly grooved than that of ponderosa’s.

Pinus attenuata (knobcone pine) also has fascicles of three yellow-green needles, which are typically three to seven inches in length and twisted. Buff colored, three to six inch, serotinous cones — that let go of seeds only after fire melts the resin — have knobby bumps on one side, and grow in bristly, dense clusters. Bark is dark with loose, scaly plates on this very long-lived, relatively small (30 to 50 foot) tree with a conical crown; it may be shrubby on poor sites. In the PNW west of the Cascades it’s found mainly in southwestern Oregon on rocky slopes at high elevations that are prone to fire (often on serpentine soils), as well as further south into parts of California and Baja.

Pinus lambertiana (sugar pine) is a very large tree (120 to 200 feet tall) that has fascicles of five pointed needles that are two to four inches in length and striped with white on all three sides. Woody cones are straight and grow very large (up to 19 inches), with straight, thick scales. Bark is reddish-brown to purplish and furrowed; on young trees it’s broken into narrow plates and on mature trees broken into long plates. It’s found at mid to high elevations in the mountains of southern Oregon (from Linn County, southward), as well as southern California, the Sierra Nevada range and northern Baja. David Douglas named the species lambertiana in honor of the English botanist Aylmer Bourke Lambert in 1826.

You may be familiar with Pinus monticola, Western white pine, since it is fairly easy to grow (despite its susceptibility to white pine blister-rust). A large, symmetrical tree (to 130 feet but smaller in cultivation), it also has fascicles of five needles, but white pine’s thin bluish-green needles have (surprise!) white lines on two sides of each 3-sided needle. Slender, curved woody cones are four to ten inches long, with scales that are thin and may be curved but without prickles. Bark is gray, thin, and broken into small rectangular or hexagonal scaly plates on mature trees. Range includes southern British Columbia, Washington, Oregon, and California’s Sierra Nevada, from sea level to about 2500 feet in elevation in moist valleys and open slopes.

The very slow-growing, often shrub-like or gnarled Pinus albicaulis (whitebark pine) also has short needles in bundles of five, thin grayish bark, and small roundish cones without prickles that remain closed on the tree at any age. Since it naturally occurs only at high elevations (near timberline) in southern B.C, the Olympics, the Cascades, east-central California and the Rocky Mountains, you won’t be tempted to grow it in your low elevation yard, but I’ll mention it as it certainly deserves our attention and concern.

Data from USFS Forest Inventory and Analysis surveys report that “as of 2016, 51% of all standing whitebark pine trees in the US were dead” and over half of that amount occurred approximately within the last two decades. Due to severe population decline, the USFWS determined that it “warrants protection under the Endangered Species Act (ESA), but … adding the species to the Federal List of Endangered and Threatened Wildlife and Plants is precluded by the need to address other listing actions of a higher priority.” The severe decline is attributed to multiple stressors, especially white pine blister rust (introduced into western North America through the horticulture trade in 1910 from Europe), but also outbreaks of mountain pine beetle (made worse by a warming climate), fire suppression and catastrophic fire, poor management, and, of course, climate chaos. UPDATE: In December 2022, this species was listed as threatened under the federal Endangered Species Act.

Whitebark pine is very long-lived, with some surviving 1,000 years. Considered a keystone species, it regulates runoff by slowing down snowmelt, controls soil erosion due to its ability to grow quickly after disturbances such as fires, and provides a rich source of food for birds like Clark’s nutcracker and mammals such as grizzly bears. It depends almost exclusively on Clark’s nutcracker for seed dispersal, but there needs to be sufficient density and seed abundance to attract the birds. More info here.

Try pines at home
If you want to add pines to your landscape, remember that it’s best to grow native trees and other plants that truly belong in your neck o’ the woods. Obtain plants propagated from source material that originated as close as possible to your site and with similar habitat features. Using such “local genotypes” helps ensure that you get plants that are well adapted to your area and preserves the genetic diversity that helps plants and animals adapt to changing conditions. Ask growers and nurseries about their sources if you’re unsure.

Provide good drainage and enough sun and space (both above and below ground) for these beauties. Whenever possible, grow them with their natural associate species, which have similar needs, to recreate a native plant community that is able to impart the most benefits to the ecosystem and result in more habitat for wildlife. And if you have the space, plant a grove!

© 2022 Eileen M. Stark

Pacific Northwest Native Plant Profile: Pacific Madrone (Arbutus menziesii)

Arbutus menziesii bark

Although it looks exotic, Pacific madrone — a beautiful broadleaf evergreen tree with a captivating and distinctive presence that transforms with the seasons — is endemic to the Pacific coast. Its exquisite attributes — fragrant flower clusters, brilliant berries, glossy leaves, twisting branches, rounded crown, and rich cinnamon-red bark that peels from a satin-smooth trunk — please all of our senses. And for the wild ones attracted to this unique gem, its ecological gifts never disappoint.

Madrona (after madroño, the Spanish name for a Mediterranean “strawberry tree”) is the name admirers in Washington give this member of the Ericaceae (heath) family, while those in California and Oregon call it madrone or Pacific madrone. British Columbians simply use the Latin genus name, Arbutus. (The epitaph, menziesii, is named after the naturalist Archibald Menzies, a naturalist for the Vancouver Expedition that explored the Puget Sound region in 1792.)

How it grows
Pacific madrone is a large, long-lived tree that naturally occurs in a climate with mild, wet winters and dry summers, although rainfall varies substantially within its range, from the east coast of Vancouver Island in British Columbia, southward through Washington and Oregon (west of the Cascades) to San Diego County. It is often found on rocky soils and other coarse soils that retain little moisture, including the dry foothills, wooded slopes and canyons of parts of California (at low to mid-elevations); within coastal redwood and mixed-evergreen forests of California and Oregon; on dry ridge tops and slopes at low to mid-elevations along the east side of the Coast Ranges and in the Siskiyou Mountains; on warm, dry, lowland sites west of the Cascades (within Douglas-fir/western hemlock forests or Oregon white oak or tan oak woodlands); and — furthest north — near sea level on rocky bluffs and low elevation slopes. Within mixed hardwood forests — that may or may not have an overstory of conifers — its tolerance to shade varies with age. While madrone seedlings do best in partial shade and young trees can handle quite a bit of shade, tolerance decreases as trees age and for those at the northern end of this species’ range. Older trees need good light to survive and often can be found  growing at an angle, twistily and desperately reaching for the sunlight that helps ensure a long life.

Wildlife value
Wild ones are drawn like a magnet to madrone trees year round. In springtime, lovely creamy white, waxy, urn-shaped blossoms provide nectar for hummingbirds, native bees, and other pollinators.

Arbutus menziesii in flower

 

Clusters of bright red berries — that ripen in autumn and may persist into early winter — feed many bird and mammal species, including American robins, varied thrushes, band-tailed pigeons, cedar waxwings, northern flickers, quail, raccoons,  squirrels, mule deer, and bears.

Arbutus menziesii (fruit)
Habitat is provided for a variety of insects, including echo blue and brown elfin butterfly caterpillars who nibble on leaves and in turn provide dinner for insectivorous birds. Shiny, leathery leaves generally remain on branches for two years, after which they turn from vivid green to burnt orange and settle to the ground where they provide a natural mulch that protects soil microorganisms and little ground-dwelling creatures. Lofty roosting and nesting habitat is also supplied, and live trees with rotting wood offer cavities for insects as well as birds that nest in trees, such as woodpeckers and chickadees. Dead and dying trees provide even more dead wood for cavity nesters and the silent decomposers that function as nature’s recyclers.

Conservation
Unlike other trees, madrone’s fine roots have adapted to search deeply into rock fractures for stored water or “rock moisture,” making it an important plant for stabilizing slopes and cliffs and preventing landslides. In addition, it’s a valuable component of many vegetation types; for example, in mixed conifer forests like Washington’s Coast Range ecoregion (Douglas-fir/western hemlock/madrone), it provides a mid-canopy story, essential for the structural diversity of the forest.

It ought to be preserved for its own sake, for the wildlife that use it, for the ecosystems of which it’s an indelible part, and, needless to say, for those of us who revere its spectacular beauty.

Tragically, the species is currently in decline throughout most of its range, for several reasons. First, sprawling development in its native habitat has stolen many mature specimens. Though tough and drought tolerant (or more precisely, drought dependent), its roots are extremely sensitive to drainage changes, compaction, grade alteration, and other soil disturbance. Because madrone belongs and successfully grows in regional arid soil conditions that many trees cannot, landowners and developers ought to protect and save this tree at all costs.

Under natural conditions, madrone depends on intermittent fires that limit the conifer overstory (typically Douglas-fir trees). Older madrone trees can survive fire and will sprout quickly and profusely afterwards due to carbohydrate reserves within existing roots. In addition, their fruit produces many seeds, which sprout on exposed soil readily after fire. But when humans suppress and prevent natural fires, the prolonged absence of fire and consequential shade—especially on moister sites—may cause madrone trees to die.

Death or damage may be also caused by several pathogens, including a foliar fungus (Nattrassia mangiferae), commonly called “madrone canker,” that reproduces via spores and causes dieback, blackening of branches, and cankers that may spread to the trunk. A root rot, Heterobasidium annosum, can also cause serious damage. Unlike fire, “disease decreases starch accumulation in the root burl, so that declining trees are less able to resprout after the aboveground portion of the tree is killed by disease.” But prevention is possible: Susceptibility to disease is exacerbated by unnatural environmental stresses such as regular summer irrigation and the use of fungicides and fertilizers. Essentially, spores are carried by water, fungicides kill beneficial mycorrhizal fungi (symbiotic associations between the roots of most plants and fungi, which protect roots from pathogens), and studies suggest that increased soil nitrogen disrupts the mycorrhizal associations between beneficial fungi and tree roots, which in turn reduce the supply of micronutrients and water to trees, thereby increasing susceptibility to disease. Madrone trees host a large number of types of mycorrhizal fungi and have been called “a major hub of mycorrhizal fungal diversity and connectivity in mixed evergreen forests” that play a large role in forest regeneration by promoting resilience to disturbance below ground.

Madrone is also affected to a small extent by sudden oak death, a disease caused by a water-borne, fungus-like pathogen, Phytophthora ramorum, which arrived in the U.S. via live plant imports of exotic ornamentals to nurseries; it is increasingly spread by human actions, including climate chaos.

Try it at home
Despite all these threats, a madrone in the wild can live hundreds of years and may grow very large—over 100 feet tall, although in cultivation they rarely exceed 50 feet after many decades. Young trees often grow fast (up to several feet per year), while older trees typically grow at a much slower pace. In the southern, drier and warmer part of its range it grows more slowly and stays smaller.

Supplemental water after establishment is highly detrimental: Madrone cannot tolerate slow drainage, standing water, or regular irrigation during summer, which makes it susceptible to disease (as do fertilizer applications). While it has a bad reputation for being difficult to establish and isn’t for the fussy gardener, knowing what this tree needs and cannot tolerate will help ensure success. In my experience, there are seven essentials to successfully growing this tree:

1. Figure out if it historically occurred in your area. Though it’s not absolutely essential that this species likely grew in your immediate area 200+ years ago — especially since much change has occurred since then — because this tree can’t just be stuck in the ground anywhere, look to nearby natural areas to see if it might have naturally occurring relatives nearby in similar soil. In its northern range, it’s usually found growing on soils derived from glacial sands or till and gravels, while in the southern and middle parts it reportedly grows on soils derived from a variety of materials.

2. Be sure your site has the right conditions: Fast-draining, non-compacted, slightly acidic soil (pH a little less than 7), and a bright location with at least a half day of sun in northerly locations. However, seedlings need partial shade to establish, so if you have mostly sun, shield them from hot afternoon rays until well established. Site plants on a slope or area that’s elevated above the surrounding area to facilitate drainage. In my yard I tried twice to grow one-foot-tall saplings in the lowest part of my yard with sad results, despite digging in extra small rocks and gravel to increase drainage. My third attempt, which I grew myself from seed, I planted atop a short, south-facing slope, again with extra rocks and gravel. I believe that the increased drainage was what was needed; however, the seedling was also very small — only three inches tall! — so that also may have helped. Note: If you live in a very warm, dry area (such as parts of California) be sure to plant this tree on a north-facing slope, rather than in hot, direct sunlight.

3. Start with very small saplings, no more than a foot tall, as older trees do not transplant well. Once they “take,” however, young trees grow quite fast (in my yard, over a foot a year). 

4. Buy plants propagated from source material that originated as close as possible to your site. Using such “local genotypes”  helps ensure that you get plants that are well adapted to your area and preserves the genetic diversity that helps plants (and animals) adapt to changing conditions. Ask growers and nurseries about their sources if you’re unsure.

5. Plant saplings in the fall, just as winter rains begin, since they establish best when they can establish roots first, then put on aboveground biomass. You can plant them in the spring, but you’ll end up worrying about how much or how often to water; during the moist days of autumn you can just let nature decide. Do not add large amounts of organic matter into the soil that could inhibit the moisture-seeking roots from penetrating to mineral soil, and do not add fertilizers that can disrupt the mycorrhizal associations between beneficial fungi and roots. Never apply fungicides or other pesticides.

6. Give them space. To allow them to get to their full and most beautiful form, plant them at least 20 feet apart and at least 25 feet away from tall trees, especially conifers that produce deep shade. Also try to minimize soil compaction, which can be detrimental.

7. Irrigate sparingly, and preferably only during the first summer or two. During my little tree’s first spring and summer it was unusually warm and dry, and I noticed some wilting of leaves on especially warm days. I carefully (and nervously!) watered it with tepid tap water (or rain water I had collected) in the mornings around its base and outwards a few feet, keeping the leaves and stem completely dry. I did this only a couple of times a week when heat was predicted, and by the end of the summer it was in fine shape and had grown well over a foot in height. During the second summer I left it on its own, and when no wilting of leaves occurred it became clear that the little tree was self-sufficient. After another foot of growth was added, I was able to fully exhale. Sometimes a little wilting of leaves isn’t serious: when cooler nighttime temperatures return the tree may bounce back, but you’ll have to be the judge at your particular site.

Baby madrone

Baby Madrone, just 4 months after planting as a 3-inch-tall sapling. [Update, 2023: At around 8 years of age, Ms. Madrone is now nearly 12 feet tall.]

 

 
Grab a partner
It’s best to match madrones with other species that are compatible below ground—those that have similar needs and mycorrhizal associations and that would naturally occur together in nature (if you already have some non-natives that you want to keep, be sure not to grow any that need summer irrigation nearby). Which native “associated species” you choose depends on what part of the region you live in.

Madrone most commonly rubs shoulders with mixed-hardwood tree species that often have some conifer overstory (without completely shading them).  A member of the Douglas-fir/tanoak forest, madrone makes up the secondary canopy, while Douglas-fir (Pseudotsuga menziesii) with tanoak (Lithocarpus densiflorus) typically create an overstory. Less commonly, madrone mingles with coast redwood (Sequoia sempervirens) along the northern California and southern Oregon coast, and with western hemlock (Tsuga heterophylla), Oregon white oak (Quercus garryana var. garryana), and Pacific ponderosa pine (Pinus ponderosa var. ponderosa) throughout much of its range. Washington’s San Juan Islands’ open woodlands support madrone with Douglas-fir and fescue (Festuca spp.), as well as other species such as lodgepole pine (Pinus contorta), Oregon white oak (Quercus garryana), and Rocky Mountain juniper (Juniperus scopulorum). In British Columbia, Pacific madrone grows alongside lodgepole pine. Other tree species associated with madrone include sugar pine, white fir, California black oak, giant chinquapin, bigleaf maple, bitter cherry and California laurel, according to the U.S. Forest Service. Small trees/large shrubs commonly associated include vine maple, black hawthorn, red-twig dogwood, willow, hazelnut, and red elderberry. Smaller shrub associates include manzanitas, Oregon grape, ceanothus, salal, oceanspray, poison-oak, gooseberry, wood rose, snowberry, huckleberry, and thimbleberry.

A. menziesii with oaks

Madrone mingles with Oregon white oak, aka Garry oak (Quercus garryana), in parts of its range.

 

Propagation
Pacific madrone are fairly easy to grow from seed. Collect fruit soon after it ripens, generally early to mid-fall. Because one berry can have up to 20 seeds, you won’t need more than one if you just want to grow a few trees.

Separate the seeds from the pulp of a ripe, red berry (if it has dried, soak it overnight to help release the seeds from the pulp). Place seeds in a small bowl of water for 15-20 minutes; discard those that float and allow those that sink to dry in a cool place out of sunlight. Dry seeds may be viable for a couple of years if stored properly in a cold, dry place. Place seeds on top of a fine seedling mix in autumn, either in a pot outdoors or in the soil where you want a tree to grow, and cover just slightly. I like to grow them in pots so I have a little more control, but I’ve had success both ways. If you choose to use pots, keep them moist but not wet, and keep them away from slugs and snails.

Madrone seeds reportedly are able to maintain dormancy for long periods (“scores of years”) in the soil, but when conditions are just right — cold but above-freezing temperatures and adequate moisture — dormancy is broken in late winter/early spring after cold stratification has weakened the seed coat. At that point pots should be moved into a somewhat warm (if possible), bright location, but with little direct sunlight—seedlings establish best in partial shade and will grow fairly slowly. Keep them moist, but not saturated. After they have developed their second or third set of true leaves they may be moved to bigger pots with fast-draining soil (I like to use a mix of sterilized potting soil and small gravel), handling them by their expendable first set of leaves, not their delicate stems. Water them when the top inch of soil is dry; I find it’s hard to overwater with fast draining soil, but do give them time to dry out slightly. Plant them out when they’re 3 to 10 inches tall, preferably in autumn, in the conditions described above. Don’t attempt to relocate them.

 

© 2017 Eileen M. Stark

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Pacific Northwest Native Plant Profile: Cascara (Frangula purshiana)

Rhamnus purshiana drupe
Of the 35+ Frangula species worldwide,
the Northwest’s representative is a lovely medium-sized tree or tall shrub. The first thing you may notice about Cascara (Frangula purshiana, syn. Rhamnus purshiana) is its texture: Thin, silvery gray bark that’s nearly smooth but with a patchy look, and oval glossy green leaves with veins so prominent that they make the surface wavy and crinkled-looking. But Cascara’s charm doesn’t stop there: Springtime brings loose clusters of small, pale greenish-yellow flowers that later become small red fruit (a drupe, each containing 2 or 3 seeds) that ripen to the deepest purplish-blue. In autumn, its leaves turn yellow to orange and may hang on in areas with mild winters.

Frangula purshiana is a member of the Rhamnaceae family; the species name relates to frangulanin, a peptide alkaloid. The epithet, purshiana, commemorates Frederick Traugott Pursh, a remarkably well-traveled (often on foot) 18th century German-American botanist who made major contributions to North American botany.
Rhamnus purshiana

How it grows
Cascara naturally occurs along the Pacific coast from British Columbia south into northern California, as well as parts of Idaho and Montana. It’s found in moist to dry shady forests and mixed woodlands, often along streams or in moist ravines at low to middle elevations, as well as floodplains. It grows up to about 30 feet tall and roughly half as wide.

Cascara and red alder look a bit alike; you can tell them apart mainly by their fruits and leaves. Cascara produces a red to deep purple drupe, while alder’s fruit is an inch-long woody fruit that resembles a cone, known as a strobile. The leaves of Cascara are shinier and smoother than those of alder, which are tightly rolled under on the edges.

Conservation
The dried bark of Cascara has been used for hundreds of years as a laxative—first by indigenous peoples and then commercially (sold as Cascara sagrada)—and the high demand for it has led to unethical harvesting from wild trees, which deprive the plants of their protective and essential bark. It is probable that this practice has heavily reduced cascara populations.

Wildlife value
Pollinators—such as hummingbirds and native bees—come to Cascara’s late spring flowers. Birds—including band-tailed pigeons, robins, tanagers and grosbeaks—as well as mammals such as raccoons and coyotes, are attracted to the pea-sized fruit. Birds like bushtits, kinglets, warblers and chickadees forage on insects found on leaves, twigs and bark. Cascara is a host plant for the caterpillars of gray hairstreak and swallowtail butterflies and more than a dozen moth species, which feed on its leaves. Mule deer and other mammals may use it as browse.

 

Try it at home
Cascara is a great choice for small yards or places where large trees wouldn’t thrive, and I don’t know why it’s not planted more often. Besides its beauty and wildlife appeal, it’s a fast grower that can take a fair amount of sun to full shade, but it does best in partial shade. Though it is drought tolerant when established (especially in shade), it will look and do its best with somewhat moist, well-drained soil that’s rich in organic matter. In general, trees planted in hot, sunny areas will need more water. Like us, Cascara shows sensitivity to toxic gases and tiny sooty particles that are belched out of fossil fuel powered vehicles, so it may be best to keep it away from busy streets and highways. It is reportedly fire resistant.

When planting multiple trees, place them about 15 feet apart (about 10 feet apart for shrubs used as a hedgerow). Cascara shrubs are a good substitute for invasive English laurel or Portugal laurel shrubs where they can be left unpruned.

Grab a partner
Cascara grows in the understory of trees such as big leaf maple, Douglas-fir, and western hemlock, where it might live alongside vine maple, red alder, willows, and red-twig dogwood.

It’s worth noting that some Rhamnus species, such as R. cathartica (“common buckthorn,” native to parts of Europe, northwestern Africa and western Asia), are invasive outside their natural range. R. cathartica was introduced as a garden plant and is now naturalized in parts of North America, probably because it leafs out earlier than native species, often contributing to their downfall.

 

© 2017 Eileen M. Stark

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Gifts of the Oregon White Oak (Quercus garryana) aka Garry Oak

Quercus garryana at Ridgefield NWR


Spring still seems out of reach
, so while we’re awaiting balmier days, let’s take a moment to appreciate some of nature’s subtle, yet generous gifts. We owe everything to the natural world and even modest contact with it refreshes and offers solace. While contemplating the obvious things that nature provides—food, water, clean air—it’s easy to overlook the little (and not so little) things.

Plants, the primary producers on this planet, belong to irreplaceable, intricate, ancient ecosystems, within which they support and depend on other species—both flora and fauna— to survive. I like to think of it as everlasting give and take. This post honors one of my favorite Pacific Northwest natives whose gifts are mammoth. Quercus garryana, commonly called Oregon white oak (or “Garry oak” by those in British Columbia and Washington), is a slow-growing, very long-lived, majestic, deciduous tree that, with time, grows beautifully gnarly. As a keystone species, oak trees are vibrant communities in themselves, and support more life-forms than any other trees in North America.

Wildlife hotspot
Late last fall, while strolling along a trail at Jackson Bottom Wetlands Preserve (just west of Portland), I was awestruck by the amount of life attracted to the broad canopy of just a single mature Oregon white oak: Visible and audible were multiple white-breasted nuthatches, black-capped chickadees, downy woodpeckers, and red-breasted sapsuckers, all busily going about their foraging business with such enthusiasm that all I could do was look upwards, my mouth agape. The birds weren’t seeking the tree’s highly nutritious acorns, which sustain many other birds, as well as insects, mammals, and reptiles—they were consuming a tasty assortment of insect herbivores, which oak trees are particularly adept at generating. Studies show that the genus Quercus hosts more caterpillars and other insect life than any other genus in the northern hemisphere. This proficiency is especially important during breeding season, when the vast majority of landbirds consume and feed their young highly nutritious insects or their larvae, and other arthropods such as spiders—not seeds or fruit. Other studies show a higher diversity of bird species in oak forests than in nearby conifer forests (although pine forests are quite exceptional as well).

Like other native keystone tree species, Oregon white oak peacefully regulates ecosystem processes like nutrient cycling and energy flow, which provides benefits to wildlife (and the rest of us) that seem endless. Besides the obvious shade, beauty, and exchange of oxygen and carbon dioxide that these trees offer (trees really are the best carbon sink), inconspicuous flowers—which typically bloom in late spring—provide for pollinators like native bees, while the buds of forthcoming rounded, deeply lobed leaves play host to the larvae of gray hairstreak, Lorquin’s admiral, echo blue, California sister, and propertius duskywing butterflies. Speaking of leaves, it typically retains dead leaves on its branches until spring, a process known as marcescense. (It’s believed that marcescense, which is more common on young trees, may serve to protect new buds on branches by discouraging browsing animals from grazing. There’s also speculation that marcescent leaves help oaks create a nutrient-rich mulch when the trees need it most —in springtime. But no one knows for sure.)

In addition, cover, perches, and nesting habitat go to birds such as woodpeckers and vireos, as well as native squirrels. Oaks’ acorns sustain squirrels and other mammals, as well as many bird species. Fallen leaves, which might provide habitat for arthropods, amphibians and reptiles, slowly break down into a rich leaf mold that supports soil-dwelling invertebrates and numerous fungi that allow neighboring plants to thrive. Sugars and carbon are provided for mycorrhizal fungi, which reciprocate with nutrients for growing plants and contribute to the soil carbon pool. Intact bark creates microhabitat for mosses, as well as lichens that supply food, shelter, and nesting material, while loose bark and twigs contribute to nest building as well as browse for deer, which in turn feed carnivores like cougars.

And as oaks deteriorate with advanced age (which can be 500 years), they continue to deliver. Dead trees can last many years as snags, which provide food, nesting material, and housing to cavity nesters like owls, kestrels, woodpeckers and chickadees, as well as bats who may roost in old holes or under loose bark.

How it grows
Elevation, climate, soil, and water persuade Oregon white oak to vary immensely in habit and size. While it thrives in cool, coastal areas and near the edges of streams and wetlands where it tolerates seasonal flooding, it also flourishes in droughty inland sites where it may grow both individually and in groves on low hills surrounded by grasslands. When it occurs on gravelly sites or rocky slopes with thin soils, it often has a shrub-like or scrubby habit. Along the blustery Columbia River Gorge, where it grows with little rainfall and atop hundreds of feet of layered basalt, harshly battered trees grow gnarled but hang on thanks to a very extensive and strong root system. As seedlings, this oak’s root mass may be ten times as large as the aboveground growth.

Within the richer, deeper, riparian soils amongst tapestries of dazzling wildflowers and grasses in the Georgia Basin-Puget Trough-Willamette Valley ecoregion of British Columbia, Washington and Oregon, it acts as a keystone structure, typically growing a very broad canopy, and reaching heights 100+ feet over hundreds of years. Gigantic root systems may grow two or three times wider than the canopy. The ecoregion includes savannas (grassland with trees scattered at least 100 feet apart), upland prairies (another type of grassland), wet prairies, and shady oak woodlands with a continuous or semi-open canopy. I’ll call them, collectively, prairie-oak ecosystems.

Endangered ecosystems
To really appreciate an oak, it’s helpful to know something about its unique ecosystems that once provided some of the richest habitat in the world. The historic range of Q. garryana stretches from low elevations of southwestern British Columbia (including Vancouver Island and nearby smaller islands) to California. In Washington, it occurs mainly west of the Cascades on Puget Sound islands and in the Puget Trough, and east along the Columbia River. In Oregon, it is indigenous to the Willamette, Rogue River and Umpqua Valleys, and within the Klamath Mountains.  

When pioneers and naturalists encountered prairie-oak ecosystems, they found a breathtakingly beautiful and rich mosaic of plant and animal life. Journals of early Oregonians described massive prairies with five-mile-wide dense forests of ash, alder, willow, and cottonwood that skirted meandering rivers within floodplains. Marshes and sloughs developed during high water periods but often dried out by late summer. At higher elevations within these forest corridors were oak and associated trees. Above the floodplains were upland prairies, filled with herbaceous plants and grasses that could tolerate the parched soil of summer, as well as winter wet. Oak woodlands stood on low hills above the valley floors, surrounded by grasslands, also known as savanna.

But the landscape was not untouched or pristine. Aboriginal peoples managed parts of the ecosystems following the last glacial period, frequently using prescribed burning to boost edible plant productivity, aid the hunting of wildlife, limit the growth of conifers, and facilitate travel, particularly in the northern parts of the oak’s range. Harvesting of plants such as camas (Camassia spp.) and chocolate lily (Fritillaria affinis) also caused soil disturbance, but their eco-cultural manipulations pale greatly compared to what came later.

Since Euro-American settlement, as much as 99 percent of the original prairie-oak communities that were present in parts of the Pacific Northwest have been lost and many rare species dependent on them are at risk of extinction. Extensive destruction and fragmentation began with settlement in the 1850s, with clearing, plowing, livestock grazing, wildfire suppression, and cutting of trees for firewood and manufacturing. Prairie wetlands bejeweled with wildflowers were drained and ditched. Later, subsidies to ranchers encouraged more destructive grazing, while urban sprawl and agricultural use—fueled by human population increase—intensified. Invasion of nonnative species, and the encroachment of shade tolerant and faster growing species—that proliferate with fire suppression—outcompeted oaks and decimated additional native flora and fauna. Prairie-oak ecosystems and associated systems still continue to disappear at human hands, and isolation of the tiny remaining fragments prevents the migration of wildlife and healthy genetic material from one area to another. Other detrimental factors include diseases and parasites, climate change, and the loss of wildlife that cache acorns and perform other essential functions.  

Conservation
Despite continual destruction, there is a renewed and growing appreciation for the diversity and beauty of these habitats, motivated by recognition that we are responsible for what’s been destroyed, an admiration for the interconnected wild species the habitat supports, and a reverence for an iconic, magnificent tree. Intervention has become intensive, and collaborations and partnerships—along with private landowners, who are key partners—are working to reverse the downward trend with preservation, restoration, and management tools, although “a major restoration challenge is restoring wet prairie habitat to a level at which it can maintain resistance to invasive species,” according to the Institute for Applied Ecology.

Regeneration of oak seedlings is essential, but is often difficult. Acorns look tough, but they are viable for only about a year and may be subject to parasitism, weather extremes, and genetic isolation. Consequently, just a small percentage become trees. Two independent studies determined that oak seedlings do best when caged, but protection from other deterrents—drought, competing plants, and rodents—is important, depending on location.

Regional conservation groups include the Garry Oak Ecosystems Recovery Team and the Cascadia Prairie-Oak Partnership.

Try it at home
While the maintenance of only fragments of a past ecosystem is a poor alternative to former richness, if you live in the ecoregion (or other impoverished oak-dominated ecosystem) and want to help, choose this native tree. Even a single isolated tree can be a critical habitat structure on the landscape. It’s the only oak native to Washington and western Canada, and the dominant one in Oregon (black oak—Quercus kelloggii—is another beautiful and valuable large tree that occurs from Lane County, Oregon, south to Baja, at low to high elevations).

An Oregon white oak tree needs a mostly sunny, well-drained site that can accommodate its eventual size aboveground (25-50 feet wide, depending on spacing) and enormous root systems described above. Those grown on poor, dry, rocky sites will grow quite a bit smaller and have a shrubby habit. When planting more than one, space trees 20 to 60 feet apart, using the closest spacing only in dry, rocky terrain. It may be most helpful to visit a nearby natural area and then try to mimic nature’s arrangement.

To maintain genetic integrity, always choose trees or seeds that originated from trees close to your location and from similar terrain. For best results, plant dormant saplings in late fall after rains begin. After watering, apply about three inches of an organic mulch to reduce evaporation and keep weeds (that can steal water and nutrients) down. I prefer low-nitrogen leaf compost, spread out to the tree’s drip line and kept at least a foot from the trunk to prevent rot. Oaks do not need rich soil, so don’t apply synthetic or organic fertilizer because most North American trees don’t need fertilizer and may even respond adversely to it. And don’t use those watering bags that only water at the base of the trunk and may promote rot

Though this species is drought tolerant, provide ample summer water, deeply and infrequently until established. During the first summer I like to water roughly every five days with about 10 gallons of water that’s applied so that it sinks in slowly. During the second and third summers, water once a week, 10-15 gallons, being sure to water out to the root zone (drip line) and beyond—root spread can be more than twice that of the crown. If severe heat and prolonged droughts appear to be stressing a young tree, provide more water. After the first few years it may do fine on its own, but do water it (deeply) if it appears to be drought stressed. Keep the area well weeded and don’t stake trees unless they are in very windy areas—they’ll grow much stronger if left unsupported. Keep in mind that soil compaction, hardscape, lawns and irrigation systems around water-sensitive oaks are a major cause of their decline in residential areasHere is more info on how to plant Oregon white oak.

Grab a partner
As with other native species, oaks will function best when grown within a habitat and community type that consists of plants that evolved together and need the same conditions. Figuring out which community occurs in your area requires a walk in a nearby natural area where species, as well as nature’s organization, can be learned. Some associate trees that might thrive with your oak include Oregon ash (Fraxinus latifolia) on moist sites, and madrone (Arbutus menziesii) on drier sites, and Pacific ponderosa pine (Pinus ponderosa subsp. Benthamiana). For shrubs, consider california hazelnut (Corylus cornuta var. californica), osoberry (Oemleria Aquilegia formosacerasiformis), serviceberry (Amelanchier alnifolia), snowberry (Symphoricarpos albus), oceanspray (Holodiscus discolor), red-twig dogwood (Cornus sericea), and tall Oregon grape (Mahonia aquifolium), depending on your location. Sword ferns (Polystichum munitum), orange or pink honeysuckle (Lonicera ciliosa or L. hispidula), fescues (Festuca spp.), and many wildflowers, including allium (Allium cernuum), camas (Camassia spp.), meadow checker mallow (Sidalcea campestris), western columbine (Aquilegia formosa, pictured right), and shooting star (Dodecathon spp.) associate in different parts of its range.

To find out which habitat type and plant communities would likely have grown in your area, check out this Ecoregional Assessment, or query your county’s soil and water conservation district or native plant society chapter. The following publications may also be helpful:
~ Georgia Basin: Garry Oak Ecosystems Recovery Team
~ Puget Trough: Prairie Landowner Guide for Western Washington 
~ Willamette Valley: A Landowner’s Guide for Restoring and Managing Oregon White Oak Habitats

 

© 2017 Eileen M. Stark

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