The coast redwood understory is a fascinating place. Next up in our review is the native redwood sorrel, botanical name Oxalis oregana.
It’s called redwood sorrel because it prefers to grow on the redwood forest floor and it’s extremely common there, sometimes forming great expansive green carpets. It ranges mostly where redwoods do, following the coast from central California up through Oregon and Washington, and just barely into British Colombia.
Redwood sorrel is native herbaceous evergreen perennial that spreads by rhizomes (which are sort of underground stems) and seeds. It grows in dense patches, mostly about 8 inches tall, in moist, quite shady areas. Its leaves are each made up of three heart-shaped leaflets.
The leaves are actually really cool. Because these plants live in the deep shade under the great redwoods, they’ve adapted with super-sensitive leaves to photosynthesize with very little light. That would be problematic during mid-day in summertime when the sun is high enough in the sky to deliver direct light to the plants but the redwood sorrel have also adapted to close their leaves, like an umbrella, when the sunlight is too direct. They also use this folding technique to conserve water during dry times and to protect themselves from heavy rains during the wet season.
The plant blooms early spring through the end of summer. The small flowers are white to pink with five petals with lavender veins.