How to grow Macadamia

Where to plant

Macadamias do best in mild, frost-free subtropical climates with regular rainfall or irrigation. Mature trees survive mild frosts and drought, but yields and nut quality suffer, and temperatures over about 90°F appear to reduce growth and production. Young trees need protection on frost nights.

They need deep, well-drained soil and shelter from wind. Air-layered trees in particular have shallow roots and blow over easily, so plant them on the lee side of a windbreak or large tree. Give them plenty of room; crowded trees crop poorly.

• Hawaii: the classic US macadamia region; the best Hawaiian orchards are at about 700 to 1,800 feet elevation.
• Central and South Florida: plant in spring in a warm, sheltered spot and cover young trees on frost nights; mature trees handle a light frost.
• Southern California: grows well in frost-free gardens; plant in spring or fall and protect young trees inland.
• Northern California: plant in April or May after the last frost and cover young trees on frost nights.
• Elsewhere: macadamia needs USDA zone 10a or warmer outdoors.

Choosing a variety

Two species are grown: smooth-shell macadamia (Macadamia integrifolia) and rough-shell macadamia (M. tetraphylla), plus hybrids such as 'Beaumont'. UF/IFAS Sarasota County notes that 'Beaumont', 'Dana White' and 'Arkin' can be found in Florida nurseries. Buy a grafted tree of a named variety for earlier, more reliable crops.

How to plant

1. Plant a grafted tree in spring, in full sun, on the protected side of a windbreak.
2. Space trees about 20 to 30 feet apart; closer planting leads to crowding within about ten years.
3. Water in well and mulch to keep the shallow roots cool and moist.
4. Stake young trees in windy sites.

Watering and feeding

Water regularly where rainfall is less than about 60 inches a year, as drought stress reduces nut yield and quality. Young trees need regular watering while they establish.

Feed 3 to 4 times a year, increasing the amount as the tree grows, guided by soil and leaf tests. Avoid heavy phosphorus: University of Hawaii notes that excess phosphorus can cause iron deficiency and yellow leaves.

Pruning and care through the year

• Little pruning is needed. Shape young trees for a strong framework and remove dead or crossing branches.
• Gather fallen nuts regularly, as squirrels and rats take them.

Harvesting

Ripe nuts fall to the ground. In Florida they mostly ripen from late November into December; in Hawaii the main harvest runs from about August to January. Gather them every 2 to 3 weeks in wet weather, before they mold or sprout.

Remove the green husks within a day of gathering, then dry the nuts in the shell in a shaded, airy place for about two weeks before cracking. The shells are very hard, so a dedicated macadamia cracker helps.