Oxalis acetosella
European wood-sorrel
Overview
Oxalis acetosella is a low, creeping perennial in the wood-sorrel family, growing only 2-6 inches (5-15 cm) tall from a slender, scaly, creeping rhizome. The thin, bright green leaves are divided into three heart-shaped leaflets like a shamrock, each about 0.4-0.8 inch (1-2 cm) wide, that fold downward at night and in bright sun. In spring it bears solitary, cup-shaped flowers 0.6-1 inch (15-25 mm) across on slender stalks, white with thin lilac or pink veins and a yellow base. Later in the season it also produces small, closed self-pollinating flowers near the ground that set seed without opening. The plant carpets cool, shaded, humus-rich woodland floors, spreading slowly by rhizome into loose mats. The foliage has a sharp, sour taste from oxalic acid, which is mildly toxic in quantity. It needs constant shade and moisture and scorches or shrivels in sun or dry soil.
Native Range
Native to Europe and temperate Asia, from Ireland and Iceland across to Japan, growing in deciduous and coniferous woodland and on shaded banks. A closely related species occurs in North America, but O. acetosella itself is Eurasian.Suggested Uses
Used as a low groundcover in shaded woodland gardens, rock crevices, and the north side of buildings, spaced 6-8 inches (15-20 cm) apart. It fills cool, moist pockets where taller plants falter. The spring flowers add detail at close range along shaded paths.How to Identify
Appearance
Size & Dimensions
Height2" - 6"
Width/Spread8" - 1'4"
Bloom Information
White, veined flowers open from April to May, scattered singly above the foliage. Each flower lasts a few days and the bloom period runs four to six weeks. Inconspicuous self-pollinating flowers follow through summer and set most of the seed.
Detailed Descriptions
Flower Description
White with lilac-pink veinsFoliage Description
Bright greenGrowing Conditions
Sun Requirements
Tolerates up to 4 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
Care & Maintenance
Care Guide
Grows in full to part shade on cool, moist, humus-rich, acidic to neutral woodland soil. It needs steady moisture and shade and will scorch in direct sun or dry out where soil drains too freely. Plants are hardy to about -30F (-34C) in zones 3-8 and need no winter protection under leaf litter. A mulch of leaf mold keeps the rhizomes cool and damp. It spreads slowly and does not compete well with vigorous groundcovers. No feeding is needed in a woodland setting.Pruning
No pruning is needed for this low creeper. Tattered foliage can be cleared in autumn or left to break down as mulch. Sections of rhizome can be lifted and replanted in spring to extend a colony.Container Growing
✓ Suitable for container growing
Minimum container size: 1 gallons