A Native “Shamrock”: Oxalis oregana

Oxalis oregana

Happy St. Patrick’s Day!

The shamrock legend can be traced to the 5th century saint who used a three-leaved plant—possibly white clover (Trifolium repens)—to demonstrate the concept of the Christian trinity. Today, oxalis cultivars, or any plants with tripartite leaves labeled as shamrocks, are sold as houseplants or outdoor plants.

Our Pacific Northwest native Oxalissometimes called wood sorrel—is a beautiful ground cover for mostly shady areas (but also more open, shrubby areas) at low to middle elevations. It has edible leaves high in oxalic acid (like spinach), and forms a lush carpet in moist to dry woodlands.

Three wood sorrel species that occur naturally in the region are Oxalis oregana (wood sorrel or Oregon oxalis), O. suksdorfii (western yellow oxalis, which occurs mainly in southwestern WA and Oregon at low elevations), and O. trilliifolia (trillium-leaved oxalis). When deciding which species to grow, pick one that naturally occurs in your area (see map links in previous sentence).

Wildlife value
Oxalis is a pollinator plant, offering its charming small flowers to native bees, syrphid flies, and butterflies. Like most flowering plants that grow under low light conditions, its blossoms are white or light colored to enable pollinators to be able to easily see them. Later in the year, Oxalis seeds may be eaten by seed-eaters like sparrows and small rodents. Its leaves serve to protect and enrich the soil.

Try it at home
Grow it in the shade of tall trees like Douglas fir and with other native woodland species such as Vaccinium spp. (huckleberry), Mahonia nervosa (Cascade Oregon grape), Gautheria shallon (salal), Polystichum munitum (sword fern), Prosartes spp. (fairy bells), Trillium ovatum (western trillium), and others.

Give it moist, acidic soil (pH 5 to 6.5), preferably rich in organic matter. While morning sun is welcome, it typically won’t do well with scorching midday or afternoon sun. In full shade and once established, it is a drought tolerant plant. Be sure you like it, though, because it will spread—enthusiastically, in the right conditions—to protect the soil and soil dwellers.

Oxalis oregana


© 2015 Eileen M. Stark

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5 thoughts on A Native “Shamrock”: Oxalis oregana

  1. I had grown a huge patch of oxalis in my native plant area over the last few years. Today I was devastated to see that it had all died back and dried up to brown leaves. We have had a much cooler summer than usual, so I am really surprised. Is there any chance that the roots survived and it will come back?

  2. Thank you very much. I will check in with the Emerald chapter! May your native garden thrive!

  3. I have a native garden in my front yard in South Eugene and would like to add more plants without great expense. Does your organization offer plant trades? I have lots of Camas seeds! I’d love some oxalis, more blue eyed grass, if anyone is thinning their natives!

    1. Sarah, I don’t have an organization (it’s just me), and I should mention that it’s best to acquire plants/seeds that were propagated from source material that originated as close as possible to your site (Portland’s a bit far north). 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. You might inquire with the local NPSO, Emerald Chapter. That said, both oxalis (which needs shade and moist soil), and blue-eyed grass (which needs more sun and moist soil) spread fairly quickly, so you should be able to just start with very few plants and then let them do their thing or propagate, using those initial plants.


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