Oxalis triangularis, also known as false shamrock, is an eye-catching bulbous perennial that makes an excellent and long-lived house plant. Bold, dramatic foliage in shades of dark purple to wine-red creates a striking contrast to blush-white flowers borne in summer. The leaves are three-lobed, hence the name of shamrock which it resembles but is not actually related to. Oxalis triangularis is native to Brazil. Its leaves have extra fascination because they open during the day and close at night.
Oxalis triangularis is borderline hardy, surviving in temperatures no lower than -3°C, so is suited to outdoor growing only in the mildest areas of the UK. Oxalis triangularis goes dormant in winter and regrows the following spring.
How to grow Oxalis triangularis
Grow Oxalis triangularis from bulbs and plant in spring or buy ready-grown plants in summer. Grow in pots or in the ground, either indoors all year or outside for the summer only. Keep watered and feed regularly during the growing season.
Where to grow Oxalis triangularis
Site in sun or partial shade outside. Indoors, place in bright light but out of direct sunlight which can scorch the leaves. A cool to warm room is best at a temperature between 15-21֯C. Avoid draughts and wide fluctuations in temperature.
How to plant Oxalis triangularis
Buying dormant bulbs in late winter is the most economical way to grow Oxalis triangularis. Plant bulbs pointed-end up, 5cm deep, in pots of peat-free, multi-purpose potting compost. Or plant in fertile, free-draining soil outside, in late spring.
How to care for Oxalis triangularis
As growth develops, increase watering so that the compost stays evenly moist while taking care not to overwater. Ensure good drainage indoors by standing pots on saucers or trays of gravel. If growing in pots on a hard surface outside, raise just off the ground so any surplus water can drain away. Feed every 3-4 weeks during the growing season with a liquid fertiliser high in potassium.
In autumn Oxalis triangularis starts to die back in preparation for winter dormancy. Reduce and then eventually stop watering the plant, keeping the compost almost dry over winter. Start watering again in early spring to encourage new growth.
If growing outside in pots, move to a greenhouse, polytunnel, conservatory or porch for winter.
How to propagate Oxalis triangularis
Propagate Oxalis triangularis by division, while dormant, in late winter. Split clumps of older, established plants into smaller clumps of bulbs and replant them at the same depth as they were growing previously.
Pests and diseases
Trouble-free to grow, given the correct growing conditions. Take care not to over-water which causes plants to weaken, rot and die.
Advice on buying Oxalis triangularis
- The species Oxalis triangularis is widely available. Less commonly available are the several other, named varieties with pink or yellow flowers, which are usually sold as pot-grown plants only
- Bulbs of Oxalis triangularis are available to order in winter or early spring from bulb suppliers and online nurseries
- Always check bulbs for signs of mould before planting, or plants for signs of damage or disease
