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Perennials
Oxalis oregana
redwood sorrel
OxalidaceaeNorth America
At a Glance
TypePerennial
HabitSpreading
FoliageDeciduous
Height4–8 inches (10–20 cm)
Width12–24 inches (30–60 cm)
Maturity2 years
Growing Zones
USDA Hardiness Zones
6 - 9Zone 6
Zone 7
Zone 8
Zone 9
These zones indicate the coldest temperatures this plant can typically survive.
Frost Tolerancehardy
Key Features
Attracts Pollinators
Deer Resistant
Native to North America
Maintenancevery low
Overview
Oxalis oregana, commonly called redwood sorrel or Oregon oxalis, is a rhizomatous herbaceous perennial in the family Oxalidaceae, native to the cool, moist coastal forests of western North America — the redwood and Douglas-fir forests from southwestern British Columbia south through western Washington and Oregon to the Santa Cruz Mountains of California. It is one of the most abundant and characteristic groundcover plants of the Pacific Northwest forest floor, forming extensive, lush carpets on the cool, deeply shaded floor of old-growth and second-growth conifer forest. The trifoliate leaves — three heart-shaped leaflets arranged like an oversized shamrock — have a remarkable light-response mechanism: the leaflets fold downward along the midrib within minutes of exposure to strong sunlight or bright conditions, recovering fully when shade returns. This nyctinasty (sleep movement) is an adaptation to the dappled light conditions of the forest floor. Leaf undersides are often suffused with purple-pink. The delicate solitary flowers, white to pale pink with pink veining, appear on slender scapes in spring and again sporadically in autumn. The leaves contain oxalic acid and are mildly toxic in large quantities. A Great Plant Pick for Pacific Northwest native gardens.
Native Range
Native to the cool, moist coastal conifer forests of western North America, from southwestern British Columbia south through western Washington and Oregon to the Santa Cruz Mountains of California, growing primarily in the understory of coastal Douglas-fir, Sitka spruce, western hemlock, and coast redwood forests in deep to partial shade in cool, moist, organic, acidic soils.Suggested Uses
Redwood sorrel is the defining groundcover of the Pacific Northwest native woodland garden, creating the characteristic lush green carpet of the old-growth forest floor in deep shade where virtually nothing else performs as well. Plant in generous sweeps under established conifers, Douglas-fir, and western red cedar, or in any cool, moist, deeply shaded position. The light-responsive folding of the leaflets adds a dynamic element to the planting — the carpet collapses and recovers with passing cloud and sunlight. Combines naturally with Trillium, Maianthemum, Dicentra formosa, Polystichum munitum, and other Pacific Northwest native forest floor species. A Great Plant Pick. Not suitable for hot, dry, alkaline, or sunny gardens.How to Identify
Appearance
Size & Dimensions
Height4" - 8"
Width/Spread1' - 2'
Reaches mature size in approximately 2 years
Colors
Flower Colors
white
pink
Foliage Colors
green
purple
Fall Foliage Colors
no change
Bloom Information
Bloom Period
~8 weeksJ
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SpringFall
Detailed Descriptions
Flower Description
White to pale pink with pink veining; solitary, five-petaled, on slender scapesFoliage Description
Three inversely heart-shaped leaflets, mid-green above, often with purple-pink undersides; fold in bright lightGrowing Conditions
Sun Requirements
Partial Shade
Full Shade
Tolerates up to 2 hours of direct sunlight daily
• Full Sun: 6+ hours of direct sunlight
• Partial Shade: 3-6 hours of direct sunlight
• Full Shade: Less than 3 hours of direct sunlight
Soil Requirements
pH Range4.5 - 6.5(Acidic)
357912
Soil Types
loampeat
Drainage
moist
Water & Climate
Water Needs
Medium
Frost Tolerance
hardy
Time to Maturity
1–2 years
Care & Maintenance
Care Guide
Plant redwood sorrel in partial to full shade in consistently moist, humus-rich, acidic soil — conditions that mimic its natural habitat on the Pacific Northwest forest floor. It thrives in the deep shade of established conifers where little else will grow, provided the soil retains some moisture through summer. Incorporate generous amounts of composted bark or leaf mold at planting. The plant spreads by shallow rhizomes and self-seeds to form colonies over time; it is not aggressively invasive. Water during summer dry spells, particularly in the first two seasons while establishing. Once established in a suitable shaded, moist position, it requires very little maintenance. Avoid alkaline soils and hot, dry, or sunny conditions. Leaves contain oxalic acid and are mildly toxic if consumed in large quantities.Pruning
No routine pruning is required. The foliage may become tattered or brown at the margins during extended summer drought or cold winters; remove unsightly leaves by pulling gently at the base. Cut back or remove any colonizing growth that exceeds the intended planting area. The plant naturally rejuvenates from the rhizome; old foliage is replaced continuously through the growing season.Pruning Schedule
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summer