Oxalis dillenii aka Common Yellow Wood Sorrel

Oxalis dillenii requires full sun and cannot tolerate shade. In its natural habitat, it grows in open meadows, fields, roadsides, and disturbed areas with full sun exposure. If growing indoors, place it in the brightest location possible, ideally receiving at least 6 hours of direct sunlight daily. South-facing windows work best for indoor cultivation.

Oxalis dillenii is native to temperate North America and tolerates a wide temperature range from USDA zones 3-10. It can survive frost and cold winters, often dying back and regenerating from rhizomes in spring. Seeds germinate when soil warms to around 55°F (13°C). The plant thrives in typical temperate summer temperatures and goes dormant during extreme cold.

Oxalis dillenii produces bright yellow flowers with five petals, each 4-10mm long, blooming from April through October. Individual flowers open for only a single day and produce nectar to attract pollinators. The plant produces 2-9 flowers per inflorescence, and a small colony can remain in bloom continuously for 2-4 months. Flowers are followed by distinctive capsules that explosively disperse seeds.

Oxalis dillenii can be propagated by seed or division. For seeds, sow in spring when soil reaches 55°F, pressing seeds lightly 1/8 inch into soil. Seeds have nearly 100% germination rate. For division, separate rhizomes in spring or early summer, ensuring each section has roots and a growing point. Unlike some Oxalis species, O. dillenii does not produce stolons, so division is limited to rhizome separation.

Oxalis dillenii is primarily an outdoor plant native to North America, thriving in USDA zones 3-10. It grows well in gardens, meadows, lawns, and disturbed areas. Plant in full sun with well-drained sandy or loamy soil. Be aware that this species can become weedy and spread aggressively via self-seeding, with seed capsules that explosively disperse seeds up to 16 feet. It may require management to prevent unwanted spread.

Oxalis dillenii is primarily pollinated by insects, particularly bees. Halictid bees are the most common visitors, along with flower flies (Syrphidae), bee flies (Bombyliidae), and occasionally butterflies like the Cabbage White. The yellow flowers produce nectar to attract pollinators. Interestingly, this species is also self-compatible and can self-pollinate, showing high seed set even without pollinators.

All parts of Oxalis dillenii are edible including leaves, flowers, seedpods, and roots. The plant has a pleasant sour, lemony flavor due to oxalic acid content. Leaves can be eaten raw in salads or cooked. Flowers make decorative, edible garnishes. Young seedpods can be eaten raw for a tangy snack. However, consumption should be limited to small amounts (a handful per day) due to oxalic acid, which can interfere with calcium absorption.

Oxalis dillenii has limited traditional medicinal uses. An infusion of the leaves has been used to treat fevers, stomach cramps, and nausea. The cooling, sour taste helps quench thirst during fevers. Externally, crushed leaves can be applied as a poultice for boils, abscesses, and minor wounds due to their astringent properties. The plant is rich in vitamin C and was historically used to prevent scurvy. Use with caution if you have gout, kidney stones, or arthritis.

Beyond food and medicine, Oxalis dillenii has one notable use: it produces a yellow to orange natural dye when the plant material is boiled. This dye can be used for coloring fabrics and fibers. The sour leaves have also traditionally been used to remove rust, ink stains, and tarnish from metal due to their oxalic acid content.

Oxalis dillenii is generally a very resilient plant with few serious pest or disease problems, which contributes to its weedy nature. Occasionally, spider mites or aphids may infest the foliage, particularly in dry conditions. Root rot can occur in poorly drained, waterlogged soils. Powdery mildew may appear in humid conditions with poor air circulation. Overall, this species is notably hardy and rarely suffers significant damage from pests or diseases.

In spring, Oxalis dillenii emerges from rhizomes when soil warms above 55°F - this is the best time for division or starting seeds. During summer, the plant is actively growing and flowering; ensure adequate moisture during dry spells. In fall, flowering continues until frost; seed capsules mature and disperse. In winter, the above-ground portions die back in cold climates, but rhizomes survive underground to regenerate in spring. No special winter protection is needed in zones 3-10.