Kowhai is a small tree native to New Zealand and bears the country's national flower. A member of the legume family, it resides in the Sophora genus, which includes eight species. The kowhai tree reaches 32 feet tall with a 19-foot spread and bears long, yellow flowers in the spring. Some species are deciduous. The kowhai tree does best in temperate maritime climates outside of its native New Zealand range.
Grow the kowhai tree in an area that receives full sun all day.
Water the kowhai tree to keep the soil moist for the first two years. After that it will tolerate short periods of drought, although providing it with an inch of water a week is ideal.
Spread a 3-inch layer of mulch 6 inches away from the trunk and spread completely under the canopy. Mulch helps retain moisture in the soil.
Fertilise the kowhai tree in the spring only if the tree isn't thriving. Use a balanced fertiliser, such as a 10-10-10, sprinkled on the soil under the canopy. Because kowhai is a legume, it fixes nitrogen in the soil and should not require supplemental fertiliser.
Prune the kowhai tree in the spring to remove dead and weak branches.
All parts of the kowhai tree are poisonous if ingested.