Kōwhai Sophora microphylla
Kōwhai (Sophora microphylla) is an evergreen perennial tree in the Fabaceae family, native to New Zealand (endemic). It grows 5–10 m (16–33 ft) tall and 3–6 m (10–20 ft) wide, wants full sun and moderate water, and is hardy to about -10 °C (14 °F). Space plants about 5 m (16 ft) apart.
Plan Kōwhai in your garden →
Free. Draw your beds, then watch it grow through the year in 2D and 3D.
Kōwhai at a glance
| Type | Perennial tree, evergreen |
|---|---|
| Family | Fabaceae |
| Mature height | 5–10 m (16–33 ft) |
| Mature spread | 3–6 m (10–20 ft) |
| Spacing | 5 m (16 ft) centre to centre |
| Sun | Full sun, at least 5 h of direct sun a day |
| Water | Moderate; drought tolerance moderate, waterlogging tolerance none |
| Soil pH | 5.5–7.5 |
| Cold hardiness | About -10 °C (14 °F) once established (roughly USDA zone 8) |
| Heat stress | Likely above about 32 °C (90 °F) |
| Flowering | from about September for 4–6 weeks (northern hemisphere; later in cold climates, earlier in warm ones) |
| Wind tolerance | Moderate |
| Pollinator value | High |
| Edible | Not grown as food |
| Native to | New Zealand (endemic) |
| Common in gardens of | 🇳🇿 New Zealand |
Is Kōwhai toxic?
- People: severely toxic
- Cats: severely toxic
- Dogs: severely toxic
- Parts: seeds, all parts
Seeds contain cytisine: poisonous if chewed (the hard seeds can pass whole).
If a child or pet may have eaten part of a plant, call a poison centre or vet straight away.
Companion planting: what to grow with Kōwhai
Good neighbours
- good With Sweet corn: "Three sisters": climbing beans use corn as a support and fix nitrogen; the benefit to the corn is modest but real in low-input soils. Evidence C
Keep apart or take care
- caution With Alliums (onion family): Onions, garlic and leeks are said to stunt beans and peas (allium root exudates may reduce nodulation). Traditional companion-planting advice; controlled trials are few, so treat it as a soft preference. Evidence D
- caution With Alliums (onion family): Beans and peas are traditionally kept away from onions, garlic and leeks. Traditional companion-planting advice; controlled trials are few, so treat it as a soft preference. Evidence D
- caution With Fennel: Fennel is reported to suppress beans and peas growing next to it. Evidence C
Questions about Kōwhai
- How far apart should I plant Kōwhai?
- About 5 m (16 ft) apart, centre to centre. A mature plant spreads 3–6 m (10–20 ft).
- Does Kōwhai need full sun?
- Full sun: at least 5 hours of direct sun a day.
- How much water does Kōwhai need?
- Moderate water. Drought tolerance is moderate and waterlogging tolerance none.
- How cold-hardy is Kōwhai?
- It tolerates about -10 °C (14 °F) once established, roughly USDA zone 8.
- When does Kōwhai flower?
- From about September for 4–6 weeks (northern hemisphere; later in cold climates, earlier in warm ones).
- Is Kōwhai poisonous to cats and dogs?
- For cats it is severely toxic; for dogs severely toxic; for people severely toxic. Seeds contain cytisine: poisonous if chewed (the hard seeds can pass whole).
- What grows well with Kōwhai?
- "Three sisters": climbing beans use corn as a support and fix nitrogen; the benefit to the corn is modest but real in low-input soils.
Sources and evidence
Evidence grade A (A: strong evidence).
- New Zealand Plant Conservation Network: flora, NZPCN
- Flora of New Zealand and Ngā Tipu Whakaoranga (Māori plant use), Manaaki Whenua – Landcare Research
Notes and assumptions
- New Zealand’s unofficial national flower: golden bells in spring feed tūī and kererū. Juvenile plants are wiry and divaricating.
Reference values for planning, not horticultural, veterinary or medical advice. Varieties, soils and local climates differ: check with a local nursery or extension service.
Related plants
- Bush bean Phaseolus vulgaris
- Garden pea Pisum sativum
- Sweet pea Lathyrus odoratus
- Runner bean Phaseolus coccineus
- Broad bean (fava) Vicia faba
- Lima bean Phaseolus lunatus
- Cowpea (black-eyed pea) Vigna unguiculata
- Yardlong bean Vigna unguiculata subsp. sesquipedalis