Five Ways to Make Your Yard More Biodiverse

Olive clubtail dragonfly resting on Mountain ash (Sorbus scopulina).

 

Every 30 seconds in the United States, a football field-sized chunk of natural area disappears due to development, according to research from the Center for American Progress. Most of the natural areas lost in the past two decades were on privately-owned land, which accounts for about 60% of all land in the country. Clearly there’s much work to be done, since only 3% of protected areas in the U.S. are on private land. Currently, only 12% of all U.S. land is protected, which is very bad news for biodiversity. 

Scientists see the goals set by the International Convention on Biological Diversity — protection of a mere 17% of land and 10% of oceans by 2020 — as completely inadequate to handle the Sixth Mass Extinction and the climate crisis. To stop the crumbling of biodiversity — defined as all the organisms on earth, well as the diversity of ecosystems in which they are found, and the genetic diversity within each species — efforts are now behind “30×30”, a global goal to protect 30% of Earth’s land and water by 2030.

President Biden issued an executive order soon after taking office that requires agency leaders to submit input and strategies for how the feds can conserve at least 30% by 2030. Reversing the cuts made by the Trump administration and targeting expansive areas will certainly have the quickest effect, but all important habitat ought to be saved or restored. If you feel hopeless or sickened by the extinction and climate crises made worse by unrestrained development, even a 30 by 30 foot space at home will help. We can’t put it off any longer.

Here are some objectives as you move forward: 

1. Focus on local native plants after removing invasives. There’s nothing terribly wrong with growing a few of your favorite plants—for example, I love certain clematis vines and irises, and I grow organic food to eat. But those plants don’t provide much, if any, benefit for wildlife, so a large portion of the remaining plants I’ve chosen are native species, most of which belong in my area and might grow together in their natural state. Besides being low maintenance (when properly sited), they are absolutely essential to creatures who developed special relationships with them over millennia.

Native species are superior to introduced plants not because they’re trendy or due to some prejudice or because I say so. Simply put, native plants depend on native wildlife and vice versa (when they are in the appropriate place—that is, areas where they evolved together). They’re adapted to local environmental conditions and their value is not based solely as a resource for humans or on appearance (although their beauty is remarkable!).

Plant diversity is strongly associated with species richness, including healthy insect-dominated food webs. As the essential structural and functional base of many of the world’s ecosystems, most insects are “specialists”—they can only survive with certain species of plants that they evolved with (as opposed to “generalist” species that can use many plants). For example, butterflies and moths need certain host plants that provide food for their young, and many native bees forage for pollen only on specific plants at specific times of year. Myriad other insects are able to use only specific native plants; if those plants aren’t around, the insects’ decline or disappearance adversely impacts ecosystems and other animal populations since specialist and generalist insects and other arthropods supply food for other wildlife. Besides habitat destruction and climate chaos, insects are challenged by additional stressors, including insecticides, herbicides, introduced species, and light pollution. To make things worse, stressors often happen simultaneously. A 2019 global review revealed that 40% of insect species could become extinct in the next few decades, with a staggering 2.5% decline in insect biomass per year, and warned of a catastrophic impact on the earth’s ecosystems. In 2020, researchers found that Earth lost more than 25 percent of land-dwelling insects in the past 30 years

Growing natives is an act of compassion for wildlife at our mercy. It helps to think of animals as individuals with emotions and personalities, not just species. Like us, they want to avoid suffering and live a decent life, and most need native plants in order to do so. Animals such as birds and frogs that eat insects directly are of course negatively affected, but other species are as well. Bobcats, for example, are obligate carnivores, but they need native plants since they typically eat animals that consume insects or plant matter. 

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.

2. Minimize lawn and be bold when it comes to sizing garden beds. The more space we allocate for native plants, the better. Lawn is an unnatural monoculture that provides almost no support for wildlife, so if it’s not needed, let it go. You can remove it with a sod cutter or spade, but to preserve precious topsoil, cut it short, then cover it with a half dozen layers of overlapping newspaper or a layer of cardboard with holes punched in to ensure drainage. Cover with leaf compost and allow it to break down over many months.

To get ideas for plant selection and how to arrange and space those plants, look to nearby natural areas that support local native plants, inquire with your local native plant society chapter, and check out my book (if you live west of the Cascades). Plant long-lived trees and shrubs for carbon sequestration and habitat, as well as privacy so that unnecessary fencing may be removed, allowing for a contribution to wildlife corridors that connect. Add associated understory plants, including ground covers that offer the best mulch

Speaking of space, growing perennials for pollinators’ sakes means providing at least several plants of the same species that are planted fairly close to each other so that pollinators can easily find them and so there’s enough of a particular flower’s nectar/pollen to go around. But spacing them evenly, in perfect clumps, isn’t necessary and often looks contrived, and lining them up like veggies in a kitchen garden is even worse, aesthetically speaking. Take a walk in a natural area and you’ll find perennials and other plants with an array of spacing—some close together, some further apart; most mingle with other species that they evolved with. Irregular drifts may occur, as if nature took a paintbrush to create rhythmic splashes. Repetition of plant groupings will result in a natural look and more habitat. Be sure to provide at least a couple of species that flower in unbroken sequence from early spring until fall.


3. Avoid pesticides and use organic methods. It’s imperative to not use pesticides (insecticides, herbicides, fungicides, etc.) and chemical fertilizers to prevent harm to beneficial creatures above and below ground at home and prevent toxins from entering waterways and killing downstream. The Environmental Protection Agency has registered more than 18,000 pesticides for use, and more than 2 billion pounds of pesticides are sold every year in the U.S. Pesticides are pervasive in aquatic and terrestrial habitat throughout the country and threaten the survival and recovery of hundreds of federally listed species. They don’t stay put and can kill non-targeted species, decrease biodiversity within soil, are linked to a decline in nitrogen fixation, mess up the complex balance between predator and prey species in food webs, require fossil fuels, and involve heinously cruel experiments on animals. And, the U.N. tells us that about 200,000 people die each year from pesticide exposure. Chemical fertilizers are also very problematic since they kill soil microbes and pollute groundwater and waterways, leading to dead zones, among other damages.

4. Minimize water runoff and maximize carbon storage. There’s much we can do with the water that enters our landscape, and it doesn’t have to take much effort. It may help to think of our yards as mini-watersheds and ask what we can do to make sure the water that leaves our properties is clean and won’t harm other species.

Rain gardens can collect water — from downspouts or hard surfaces where water accumulates — and slow the flow of water, cleaning it as it slowly soaks into the ground and recharges aquifers. Other elements like bioswales, permeable paving, coniferous trees, and even rain barrels can manage water responsibly in our landscapes, reducing runoff that overwhelms storm drains and pollutes waterways. But it’s the plants themselves (along with soil) that effectively filter water and store carbon. Fully and diversely planted gardens — that include long-lived large trees, shrubs and lower plants — are best at cleaning water, preventing runoff, and sequestering carbon; more so than lawn or beds that are mostly wood chips. 

Halictus ligatus on Erigeron speciosus.

Although keeping your soil covered (with plants or mulch) is a good thing for carbon storage, moisture retention and erosion control, always leave some areas with bare soil (fallen leaves and small amounts of light compost are okay), particularly in areas that face south or east. Here’s why:  70% of native bees (such as this “sweat bee,” Halictus ligatus, shown) nest in the ground (the rest raise their young aboveground in cavities, stems, tunnels or crevices). Using thick layers of wood chips, bark dust, or other such substances prevents them from being able to create their nests and if applied after nests are complete, entombs and kills the developing bees.

Also, if you grow veggies, keep tillage to a minimum, if at all. Tilling soil speeds up the decomposition of organic matter, causes erosion, releases carbon dioxide into the air, exposes weed seeds to light, destroys mycorrhizae hyphae, and generally makes soil less fertile. Unnecessary fertilizer will also release more carbon. 

Erosion concerns? Choose native plants with dense, fibrous root systems to control erosion on slopes. In the Pacific Northwest, depending on your location and conditions, consider Douglas-fir, big-leaf maple, vine maple, Oregon white (Garry) oak, madrone, serviceberry, salal,  kinnikinnick, red-twig dogwood, oceanspray, tall Oregon grape and Cascade Oregon grape, western mock orange, red-flowering currant, snowberry, western sword fern, inside-out flower, and many others.

Bushtit nests require moss, spider silk, and other natural substances.

5. Add natural elements and be lazy. Wild species need secure, dry places to spend the winter, pupate, or seek cover during bad weather, and places to raise their young:  (1) Leave the leaves on soil. (2) Include rotting logs and other dead wood in shady spots to supply the perfect home for certain invertebrates and fungi. (3) Introduce brush piles to provide shelter and maybe even nest sites for some birds. (4) If you’ve dug up rocks from your soil, create smooth rock piles or stone walls without mortar to provide cover for wildlife like amphibians and reptiles, as well as arthropods. Making all these elements as large as possible and placing them in quiet areas works best. (5) If you must “clean up,” don’t do it in fall or winter. Instead, wait until late spring and do as little as possible so that those taking cover won’t be disturbed and so that birds can find building materials for their nests, such as moss, lichen, twigs, spider silk, and dried leaves (see bushtit nest, pictured above). If all this sounds messy, it is, but it’s also easy and exactly that characteristic that supports the greatest garden biodiversity! 

Last but not least, give wildlife a drink. All animals — from birds and dragonflies to frogs and salamanders — need water, so include a gently sloping bird bath or more elaborate water feature like a pond, and perhaps a plate full of watery gravel to help creatures thrive. Although the latter is most important during dry weather, birds need water year round to keep their feathers clean and waterproof. Since many urban streams have been buried, wetlands drained, and drought is upon us, it’s the least we can do.

Golden-crowned kinglet and Townsend' warbler.

© 2021 Eileen M. Stark

Pacific Northwest Native Plant Profile: Red-twig Dogwood (Cornus sericea)

Cornus sericea ssp. occidentalis

Red-twig dogwood is one of those multitalented shrubs that grows in a variety of moist habitats, provides significant wildlife habitat, and keeps us enthralled year round. Also known as red osier dogwood and creek dogwood (among other common names), it is a multi-stemmed, deciduous, long-lived and fairly fast-growing shrub that develops into an open, somewhat rounded thicket. Its common name comes from signature reddish stems which become brightest in winter. Botanically speaking, it’s known as Cornus sericea (syn. Cornus stolonifera). Sericea comes from the Latin “sericatus,” which means “silky” and describes the soft texture of the leaves and young twigs. Stolonifera refers to its lower stems or branches that tend to tiptoe horizontally and grow roots when they touch the soil.

Besides its vibrant red stems, this plant has oppositely-arranged, deep green leaves that turn an array of colors as the days shorten in autumn. On this sunless late November day in my back yard, the leaves range from a soft gold and pale orange to deep red, and they’re becoming more purplish-red each day. Come spring, four-petaled creamy white flowers will appear in clusters in May to July and will be tailed several months later by soft white to pale blue fruit (shown above) that may persist into winter if the birds don’t devour them.
Cornus sericea

How it grows
Red-twig dogwood has a large range—from Alaska and northern Canada from coast to coast, and as far south as Virginia in the east and Chihuahua, Mexico in the west, at low to middle elevations. There are two subspecies: C. sericea ssp. occidentalis, which occurs in the Pacific Northwest, Alaska, California and British Columbia, and C. sericea ssp. sericea, which is found much more widely. Differences are miminal, with the latter having slightly larger flower petals and fuzzier leaves and shoots. Both typically occur in moist, open sites such as meadows, bogs, floodplains, and near shorelines, but they also can be found under forest canopy as well as within more open woodlands in or near riparian areas.

Wildlife value
Red-twig dogwood is important for providing diverse structure, cover, nesting habitat, and a variety of edibles for insects, mammals, amphibians, and a large number of bird species. Bees and other pollinators, such as butterflies, use the flowers for nectar and/or pollen. Birds (including waxwings, thrushes, band-tailed pigeons, northern flickers, and grosbeaks), small mammals, and bears dine on its fruits—one or two-seeded drupes which are reportedly very high in fat—in summer and fall. According to the US Forest Service, “moose, elk, deer, bighorn sheep, mountain goats, beavers, and rabbits” commonly browse the stems; twigs and new shoots provide especially delectable and nutritious winter browse. Last, but not least, this shrub provides cover and important nesting habitat for songbirds, small mammals and amphibians, as well as host plants for the larvae of butterflies like the echo blue butterfly.

Cornus sericeaTry it at home
Although fairly shade tolerant, plants growing in full sun typically grow much more compactly than those in shade, usually bloom more profusely, and exhibit more stem color. Depending on the amount of sun it receives, red-twig dogwood can grow from about 6 to 16 feet tall, and nearly as wide, so it may be best to leave it out of very small gardens. If you have the space, use it in any moist area where you’d like spectacular aesthetic appeal as well as valuable wildlife habitat: At the back of a border, next to a rain garden, as a somewhat open screen, as part of a large hedgerow, or to stabilize eroding soil on slopes. Plant it in the fall to give it an easy start in life, adding some leaf compost if your soil is in poor shape. Allow future leaves to stay where they fall.

Damp soil is important, and slow-draining soil is not a problem (although this plant shouldn’t have its feet immersed in water for prolonged periods). Though its tolerance for drought isn’t terribly high, with a little shade and soil that’s rich in organic matter, infrequent summer watering during excessively hot periods should be all that is needed once it’s established (typically just a couple of years). And, allowing for a dry period at the end of summer is actually a good and natural thing (as long as the plant looks healthy), since a bit of drought prepares the plant for winter. Red-twig dogwood is often planted at restoration sites, which are rarely watered afterwards, and most usually do fine.

Grab a partner
Since red-twig dogwood grows in such a wide range of habitats, there are a number of plant friends with which it would like to live. For best ecological and gardening results, choose associated native plants that live in communities that currently grow or likely would have grown in your immediate area. In the Pacific Northwest, some of the plants that closely associate with red-twig dogwood include western redcedar (Thuja plicata), Douglas-fir (Pseudotsuga menziesii), vine maple (Acer circinatum), alder (Alnus spp.), willow (Salix spp.), aspen (Populus tremuloides), paper birch (Betula papyrifera), gooseberries (Ribes spp.), black hawthorn (Crataegus douglasii), lupine (Lupinus spp.), aster (Symphyotrichum spp.), and many others.


© 2016 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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A Winter Delight: Licorice Fern (Polypodium glycyrrhiza)

Licorice fern (Polypodium glycyrrhiza)

When many Northwest ferns have said adiós to most of their aboveground growth and have nearly left the stage, enter licorice fern. If you have it in your yard you might forget it’s there until the soft rains of autumn release it from its dormancy. Then — when you least expect it — bright green, featherlike fronds (to about 12 inches) gradually appear to help brighten the landscape all winter long. Although licorice fern may stay evergreen where it is well established, out of harsh sunlight, and receives some moisture in the form of mist or from a watering can, it is typically a summer deciduous plant. It is a primary producer for other inhabitants within the ecosystem, including insects, birds, and other animals.

Its botanical name, Polypodium glycyrrhiza, means “many footed” and “sweet root,” and refers to creeping rhizomes that taste like licorice (which I’ve yet to try). Native Americans used the rhizome to sweeten foods and unpalatable medicines, but they also used it as medicine itself, to treat sore throats and upper respiratory infections. Modern herbalists use it for similar purposes.

How it grows Licorice fern on American elm
Licorice fern is one of those multitalented plants that occurs naturally in several habitats. The next time you walk under a massive, mature deciduous native tree like big-leaf maple or even a nonnative giant, such as American elm (native to the eastern U.S.), look upwards and there’s a good chance you’ll find it growing as an epiphyte on trunk and branch bark, particularly in crotches or on horizontal limbs that usually stay wetter than vertical ones. But it’s also found hugging dead or dying wood like logs and stumps, and as a lithophyte in rocky outcrops and mossy ledges (pictured, below).

Licorice fern (Polypodium glycyrrhiza)

 

 

 

Licorice fern naturally occurs in cooler parts of the Pacific Northwest (west of the Cascades) and near the California coast (as well as small sections of the Sierra Nevada), at low elevations. Disjunct populations in Idaho and Arizona are listed as imperiled.

 

 

Rescue mission
The ferns that now grace my yard were rescued from mature street trees that had the misfortune of being cut down or blown down in my neighborhood. The trees’ upper branches were nearly covered with the ferns, so when the fallen limbs were in the street awaiting transport, I peeled off bark adorned with the featherlike fronds, their roots firmly and securely attached to the bark. Sections of the leafy mats were placed under native shrubs and in shaded rocky areas in my yard, where the soil is fairly rich and slightly acidic, and where moss grows readily (and not too far from the hose, since I figured they would need to be kept moist for a couple of summers). I also placed some logs (leftover from fruit tree prunings) under or immediately next to those without the company of rocks. Now the mats have come to life again, and I think they are quite settled in, judging by a new little plant that’s appeared about 10 feet from its parents—spores are in the air!

Licorice fern (Polypodium glycyrrhiza)Try it at home
If you’d like to try growing licorice fern in your yard, pick a spot that’s naturally mossy, since most areas that support moss ought to be able to support this fern. And be sure that you can get to it easily with a watering can while the plants are young; they will need to be kept moist—but not saturated—until they’re established, at which time they will become self-sufficient (except during exceptionally hot periods when dormant plants will appreciate an occasional splash of water).

If moss isn’t growing in your garden, try to nestle a plant between shaded, half-buried rocks that have been enhanced with a slightly acidic, humusy and well-draining soil amendment like leaf mold. Or, try licorice fern’s close relation, Polypodium hesperium—it can take drier conditions and grows naturally in rocky places on both sides of the Cascades. Its short stature makes it a lovely addition to nooks and crannies of stone walls, as well as a candidate for creeping through a mostly shaded rock garden. Licorice fern’s other Northwest relative, P. scouleri, is a leathery-leaved gem that grows along the foggy coastline from British Columbia, south into California. But it is reportedly difficult to cultivate so should just be left alone to bask in the ocean’s salty mist.

As always, buy all native plants from reputable nurseries and never harvest from the wild. Or, rescue them from doomed situations, preferably at a time that will benefit the transition.

© 2015 Eileen M. Stark

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What Makes Leaves Change Color?

Populus tremuloides (quaking aspen)

I’ve written quite a bit about the importance of leaf “litter” on the ground, so here’s a little info on how it gets there and what conditions make for the most vibrant leaves. While it’s understandable to think that it is the cooler temperatures of the fall season that bring about color change, there are several other factors. Besides temperature, sunlight and soil moisture influence the quality of autumn leaf color. But the process that instigates the show is actually more of a chemical process brought on by less daylight.

Darkness rules

Most plants are quite sensitive to each day’s length of darkness. In early fall, when nights begin to lengthen, the cells near the joint of the leaf and stem in deciduous trees and shrubs are triggered to divide quickly. This corky layer of cells (the abscission zone) begin to block transport of essentials such as carbohydrates from the leaf to the branch, as well as the flow of minerals from roots upward to leaves.

When plants are actively growing, green chlorophyll is constantly produced in the leaves. But in autumn, when the connection between the leaf and the rest of the plant gets more and more obstructed, chlorophyll replacement slows and then stops completely. This is when autumn colors are revealed: Normally masked by chlorophyll, yellow pigments called xanthophylls and orange pigments known as carotenoids become visible when chlorophyll shuts down. Red and purple pigments come from anthocyanins which are created (in some species) from sugars within the leaf and it’s speculated that they are a defense mechanism that helps some plants fight herbivores like aphids.

Spiraea betulifolia var. lucidaAs fall moves forward, the cells in the abscission layer become drier and weaker and leaves eventually part company with the plant. Many trees and shrubs lose their leaves when they are still colorful (making for some gorgeous mulch!), while some retain the majority of their foliage through much of winter, though their leaves lose color fairly quickly. Like chlorophyll, the other pigments eventually break down in light or when frozen. The final pigments are tannins, which look brown. An example is the Oregon white oak (or Garry oak), which appears golden for just a few days before turning brown.

Recipe for color

Low temps (but above freezing) and ample sunlight following formation of the abscission layer cause quick destruction of chlorophyll and promote the formation of bright colors in some species. Stress from drought during the growing season can sometimes trigger early formation of the abscission layer, resulting in leaf drop before they have a chance to develop fall coloration, so a growing season with ample moisture that is followed by somewhat dry, warm, sunny, calm fall days with cool, frost-free nights provides the best recipe for bright fall colors.

Plant natives!

Besides offering the most ecological benefits, some native species grown in their native ground offer wonderful fall color that rivals that of nonnative plants. Here in the Pacific Northwest, some of the most vibrantly colored leaves occur on natives such as paper birch, black hawthorn, Oregon ash, quaking aspen (pictured, top), golden currant, vine maple, serviceberry, and red-twig dogwood. Enjoy!

 

© 2015 Eileen M. Stark

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Ban Neonicotinoids in Portland

painted lady butterfly

The most widely used pesticides in the world, neonicotinoids (often called neonics) are a highly toxic, pervasive, relatively new class of insecticide. Following massive bee die-offs from neonic applications in the U.S. and Canada, last year Eugene became the first U.S. city to ban the use of neonics from city property. Similar bans in Seattle, Sacramento, and Spokane quickly trailed, and now Portland’s City Council is considering comparable—and crucial—affirmative policy at the local level, since higher government continually fails to offer protection from this growing environmental threat. The U.S. Fish and Wildlife Service decided last year to phase out neonics in its wildlife refuges, making it the first federal agency to restrict neonics, but the U.S. Environmental Protection Agency has yet to act.

Hundreds of studies indicate that neonics are wreaking environmental havoc: They not only disastrously kill or debilitate native bees, honeybees, and other pollinators like butterflies and moths, but also other ecosystem members such as birds, aquatic species, and mammals. Neonics are systemic, taken up through a plant’s vascular system and exuded in the pollen and nectar. Even miniscule amounts adversely affect central nervous and immune systems, cumulatively and irreversibly. If a victim such as a bumblebee isn’t killed outright, its failed immune system will succumb to ostensibly “natural” parasites and pathogens like Bombus bifarius on Aster foliaceusfungal, viral or bacterial infections. Birds—the majority of which consume and feed their young insects—may be poisoned directly or go hungry due to a lack of insect biomass; scientists predict widespread reproductive dysfunction in birds due to neonic exposure.

Since neonics are water soluble, they are very prone to runoff and groundwater infiltration where they accumulate and persist for any years. Aquatic contamination has reached toxic levels in some areas and is expected to cause serious and far-reaching impacts on aquatic food chains.

The cumulative, persistent, and irreversible nature of neonics ought to raise some serious red flags. Human children may also be at risk to this neurotoxic class of pesticides due to their developing bodies and immune systems and tendency to be exposed to problematic substances while playing outdoors.

What we can do

We can voice our support for the proposed ordinance—which also recommends that local retailers label plants, seeds, and products containing neonics—by contacting Portland’s mayor and commissioners by March 31. Personally, I’d love to see this ban go further, as would Commissioner Amanda Fritz, but a ban on city property is a good first step.

We can also take action at home by eliminating pesticides and growing beautiful wildlife-friendly gardens. Besides chemicals, another major threat to wildlife is the lack of natural foraging areas. In our own yards we can attract and feed pollinators by including a variety of nonhybridized—preferably native—plants that will collectively flower from early spring through fall. Native plants that naturally occur in our region are best for all indigenous fauna because they supply the food and shelter that wild species require to survive and they need no synthetic pesticides or fertilizers.

 

© 2015 Eileen M. Stark

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City Birds, Country Birds: Who Lives Longest?

American robin (juvenile) © 2014 Richard P. Weber

A study published recently in the journal Ecology reveals that some birds actually might live longer in urban or suburban settings, which ought to persuade those of us living in such areas to continue or strengthen our welcome of wild species in our yards.

Researchers used data collected over a 12-year period by “citizen scientists” to determine whether some species fared better in rural areas vs. much more heavily populated ones in the vicinity of Washington D.C./Maryland. Some native birds, like American crows, and nonnative species such as rock doves and house sparrows have long been known to flourish in urban areas. But for most bird species, the extensive loss of natural habitat and the increase of human disturbance generally cause profoundly negative effects on their lives.

In this study, four species coped better than their more sensitive country cousins. Gray catbirds (rarely found west of the Cascades) and northern cardinals (found mainly in the eastern half of the US) were found to live longer in urban areas than rural, whereas American robins and song sparrows apparently live longer in suburban spaces than rural. Three other east coast species studied showed no difference in longevity in the various habitats.

The study’s authors acknowledge that further study is necessary. For one thing, longevity doesn’t necessarily mean that the birds are successfully breeding and are without stresses; the study didn’t investigate the fecundity of the birds (reproduction often declines due to constant city noise and the acoustics of human-made hard surfaces, both of which make it difficult for birds to communicate), and the birds they studied are those that have adapted, to some extent, to the presence of people and our machines, impermeable surfaces, and lights. Needless to say, the multitude of species that need quiet, undisturbed habitat, or have very specific needs can’t be studied in populated areas since they typically wouldn’t be found there.

Nonetheless, the results show that some species are more adaptive to our presence than others (such as the varied thrush that requires dark, peaceful, mature forests in which to breed). Although urban and suburban areas generally host more predators (dogs, cats, and raptors attracted to bird feeders), roads and vehicles, noise, reflective glass, and chemicals, the more adaptive birds may respond well to backyard bird feeders, artificial nest boxes, dead wood, and water sources, and the renewed interest in growing native plants in our yards. It’s highly likely that they are also able to live longer because most of their natural predators have been driven away or killed off.


© 2014 Eileen M. Stark

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A Date with a Varied Thrush

Varied thrush

Male Varied thrush perched in red-twig dogwood 


It’s unmistakably autumn
when the strikingly beautiful Varied thrush begins appearing in Pacific Northwest yards, parks, and natural areas. That’s varied, as in Ixoreus naevius, though I’ve also seen various other thrushes—Swainson’s and Hermit—feeding in residential areas from time to time. The scientific name given to this robin-sized bird comes from the Greek ixos, which means “mistletoe,” and oros for “mountain” and the Latin naevius, which translates to “spotted or varied.” If my math is correct, that adds up to “varied berry-loving mountain bird,” or some such.

Since reading the State of the Birds report I’ve felt a twinge of anxiety about whether or not I’d see them this year, as I have each fall and winter since I began creating our “real” garden. Sadly, the Varied thrush is one of dozens of species included on the list of “Common Birds in Steep Decline” that have lost more than half of their global populations within the past 40 years. But just a few days ago I spotted a female rummaging on the ground through the fallen leaves that blanket our yard’s soil, as if she had forgotten where she put her keys: She’d grab a dry leaf in her bill, toss it aside as she hopped backwards, and then search the ground. She was looking for dinner, of course, and apparently found some tasty morsels in the form of insects, slugs, or other arthropods who were hoping to get through the winter under protective leaf “litter.” Varied thrushes also eat fruit and nuts (primarily acorns) during winter and I wondered when she’d return to find the rose hips, patiently dangling off my clustered wild rose (Rosa pisocarpa), as she (or her cousin) had done last year. Apples are also reportedly a favorite food in fall.

Male varied thrush rummages through fallen leaves.

A male Varied thrush rummages through fallen leaves to find food.

Most thrushes wear earthy colors on purpose—so they can be difficult to spot—but this species can be especially tough to see since their gorgeous plumage is reminiscent of dappled sunlight or pumpkin-colored leaves on a forest floor. And they’re timid and wary of people, so you may be more likely to hear one than to see one. But hearing their call in the woods rarely helps locate one, since their ethereal, somewhat mournful voice seems to pervade a peaceful forest. Let’s honor their need to be left alone—sometimes it’s enough just to hear them to be struck by their beauty.

Birds of a feather
Fall through winter, Varied thrushes gather together in flocks, collectively known as a hermitage—a fitting description considering their obligation to be concealed. In the city they act slightly bolder than in quiet forests, coming to within about 15 feet of the house to feed, as well as perch and survey in leafless trees. Their range encompasses the boreal forests of Alaska and the Yukon, southward along the west coast to California, as well as east to Alberta, Idaho, and western Montana. National Geographic records their winter range as “coastal Alaska to southern California and parts of northern Rockies,” but judging by this enthusiastic news account, sightings in southern California may be somewhat rare.

Varied thrush female or immature

Female and immature Varied thrushes look similar.

During the remainder of the year these birds retreat to mature, misty, hushed forests that are dominated by tall conifers and lush ferns, and dine on mostly insects and other arthropods. Many migrate north as the days lengthen. In spring, the female creates her nest in streamside shrubs or conifers, typically 5 to 15 feet above ground. According to the Cornell Lab of Ornithology, the nest resembles a robin’s nest: “The female gathers nest material and weaves an outer layer of fir, hemlock, spruce, or alder twigs. She adds a middle layer with rotten wood, moss, mud, or decomposing grass, which hardens into a dense cup about 4 inches across and 2 inches deep. Finally, she lines the cup with fine grasses, soft dead leaves, and fine moss, and drapes pieces of green moss over the rim and outside of the nest.” Two to six eggs, blue with speckles, are laid and incubated by Mom but the hatchlings are tended by both (monogamous) parents; they fledge in about two weeks. They are fed arthropods, as are the majority of land birds. Two broods are produced when possible.

Since these birds thrive in old growth forests, logging is having a profoundly negative impact on their numbers, as will climate change. Window strikes are also responsible for many deaths. Want to help them and see them in your yard?

♦ During fall, winter, and early spring, don’t remove the leaves, twigs, bark, and other dead wood that have fallen from trees onto the soil.

♦ If your yard was historically forest, grow the trees that likely once grew there to provide food and roosting or nesting sites. In coastal B.C., Washington and Oregon, choose Sitka spruce (near the coast), Douglas-fir, western hemlock or western redcedar; in northwestern California choose coastal redwood, Sitka spruce, and red alder.

♦ Thrushes are mainly insectivorous, so add additional “associate” native plants that would naturally grow with the trees to supply extra helpings of native insects and other arthropods.

♦ Include native plants that produce fruits, nuts, or seeds to provide additional forage. Depending on your location, madrone, cascara, garry oak, wild rose, huckleberry, elderberry, honeysuckle, salal, thimbleberry, and dogwood might be good choices.

♦ Be sure birds can see your window glass, not a reflection of the sky. Check out these tips to help birds avoid reflective glass.


© 2014 Eileen M. Stark

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