Redwood Sorrel
Oxalis oregana
Family: Oxalidaceae
What it is like
Oxalis oregana is an evergreen Perennial growing to 0.2 m (0ft 8in). See above for USDA hardiness. It is hardy to UK zone 7. It is in leaf all year, in flower from May to July. The species is hermaphrodite (has both male and female organs) and is pollinated by Insects. Suitable for: light (sandy), medium (loamy) and heavy (clay) soils and prefers well-drained soil. Suitable pH: mildly acid, neutral and basic (mildly alkaline) soils. It can grow in full shade (deep woodland) semi-shade (light woodland) or no shade. It prefers moist soil.
Height (m): 0.2
Where it is found
Redwood forests. Moist woods.
Western N. America - Washington to California.
Conservation Status:
Countries/locations it is found in
How it is used
Food
Rating: 3
Leaves - raw or cooked. A acid, flavour, it is especially adored by children and makes an excellent addition to mixed salads. The leaves can be harvested all year round. A mass of the leaves and stems can be allowed to ferment slightly when they make a tasty dessert. A sort of rhubarb pie can be made from the leaf stalks. The leaf stalks are very thin - you would need an awful lot for a pie. Use in moderation, see notes above on toxicity. Flowers - raw. A pleasant acid flavour.
Medicine
Rating: 1
A decoction of the whole plant has been used as a wash in the treatment of rheumatism. The fresh juice of the plant has been used as eye drops to ease sore eyes. A poultice of the wilted leaves has been used as a dressing on boils, sores and on swollen areas of the skin.
Antirheumatic: Treats rheumatism.
Ophthalmic: Treats eye complaints.
Poultice: A moist, usually warm or hot, mass of plant material applied to the skin in the treatment of burns etc.
Other
Rating: 3
A good ground cover plant for a woodland garden, though it can be invasive. It needs weeding for the first year or so.
Food Forest: Plants for Edible Forest Gardens and Food Forests.
Ground cover: Ground Cover
How it is grown
Easily grown in a moisture-retentive humus-rich soil in shade or dappled sunlight. Succeeds in dense shade. Grows well in a wild or woodland garden. Plants can be very invasive when in suitable conditions. Plant is growing very vigorously in quite dense shade under an Elaeagnus shrub in Cornwall - it stays green all year round and is fairly productive. The plant is heat tolerant in zones 9 through 7. (Plant Hardiness Zones show how well plants withstand cold winter temperatures. Plant Heat Zones show when plants would start suffering from the heat. The Plant Heat Zone map is based on the number of "heat days" experienced in a given area where the temperature climbs to over 86 degrees F (30°C). At this temperature, many plants begin to suffer physiological damage. Heat Zones range from 1 (no heat days) to 12 (210 or more heat days). For example Heat Zone. 11-1 indicates that the plant is heat tolerant in zones 11 through 1.) For polyculture design as well as the above-ground architecture (form - tree, shrub etc. and size shown above) information on the habit and root pattern is also useful and given here if available. The plant growth habit is a clumper with limited spread. The root pattern is rhizomatous with underground stems sending roots and shoots along their length.
Propagating it: Seed - best sown as soon as ripe in a cold frame. Prick out the seedlings into individual pots when they are large enough to handle and plant them out in late spring or early summer. Division in spring. Larger divisions can be planted out direct into their permanent positions. We have found that it is better to pot up the smaller divisions and grow them on in light shade in a cold frame until they are well established before planting them out in late spring or early summer.
Best place to grow: Woodland Garden Dappled Shade; Shady Edge; not Deep Shade; Ground Cover;
Habit: Perennial
Hardiness: 6-9
Growth:
Soil: Light (sandy), medium, heavy (clay)
Shade: Full shade, semi-shade, no shade
Moisture: Moist
Things to keep in mind
The leaves contain oxalic acid, which gives them their sharp flavour. Perfectly all right in small quantities, the leaves should not be eaten in large amounts since oxalic acid can bind up the body's supply of calcium leading to nutritional deficiency. The quantity of oxalic acid will be reduced if the leaves are cooked. People with a tendency to rheumatism, arthritis, gout, kidney stones or hyperacidity should take especial caution if including this plant in their diet since it can aggravate their condition.