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Macadamia

Macadamia integrifolia

An Australian rainforest tree with rich, buttery nuts inside very hard shells. Most cultivars are smooth-shell (M. integrifolia), rough-shell (M. tetraphylla) or hybrids of the two, and grafted trees bear for decades.

Tree facts

Scientific name
Macadamia integrifolia
Origin
Eastern Australia (Queensland and New South Wales)
Tree size
30–40 ft; can be kept at 15–20 ft with pruning
Growth rate
Slow to medium
Sun
Full sun
Soil
Deep, rich, well-drained soil. Shallow roots blow over easily in hurricanes.
Soil pH
5.0–6.5
Pollination
Partly self-fertile; planting two cultivars raises yields
Cold hardiness
Young trees are damaged near 28–30°F; mature trees take brief dips to about 24–26°F
USDA zones
9b–11
Years to first fruit
4–5 for a grafted tree; full crops at 8–12 years
Season
Sep–Mar
Water
About every 10 days once established, without rain; more in heat, in pots and while young
Feeding
About every 90 days, Feb–Aug
Pruning
Mar–Apr
Taste
Rich, buttery, creamy and lightly sweet
Nutrition
High in monounsaturated fat, with fiber, thiamine and manganese

Is macadamia safe to eat? Edible and toxic parts

What you can eat

  • Nut kernel, raw or roasted
  • Pressed oil

Toxic parts and cautions

  • Toxic: Macadamia nuts are toxic to dogs. Even a small handful can cause weakness, vomiting, tremors and fever. Keep fallen nuts picked up.
  • Take care: A tree nut allergen. Anyone with a tree-nut allergy should avoid it unless an allergist says otherwise.
  • Good to know: Grow only the two edible species from a reliable nursery. Some wild macadamia relatives have bitter nuts containing cyanogenic compounds.
  • Good to know: The shells are extremely hard. Crack them with a proper macadamia cracker, not a hammer held by hand.

Pets: Toxic to dogs; symptoms usually start within 12 hours and pass in a day or two, but call a vet. Keep cats and other pets away from the nuts too.

How to eat and enjoy macadamia

  • Raw or roasted and salted
  • White chocolate macadamia cookies
  • Macadamia-crusted fish (Hawaii)
  • Nut butter and milk

When it's ripe

Nuts drop when mature. Gather them every week or two, remove the green husks within a day, and dry the nuts in the shell for 2–3 weeks in a dry, airy place before cracking.

Storing it

Dried nuts in the shell keep for months somewhere cool and dry. Shelled nuts go rancid quickly; refrigerate or freeze them.

Macadamia varieties (8)

  • A4

    A modern Australian cultivar with a high share of kernel to shell.

    Origin: Australia

  • Beaumont · also 695

    An Australian hybrid with thin shells and high yields, widely planted in home gardens.

    Origin: Australia · Taste: Sweet, creamy

    Nuts often stay on the tree and need picking.

  • Cate

    A rough-shell type grown in California, with large nuts.

    Origin: California · Size: Large

  • Ka'u · also 344, Kau

    An upright, wind-resistant Hawaiian cultivar with good kernel quality.

    Origin: Hawaii

    Stands up to wind better than most.

  • Kakea · also 508

    An older Hawaiian commercial cultivar with good yields.

    Origin: Hawaii

  • Keaau · also 660

    A University of Hawaii cultivar with an upright, compact habit.

    Origin: Hawaii

  • Mauka · also 741

    A Hawaiian cultivar suited to higher, cooler sites.

    Origin: Hawaii

  • Purvis · also 294

    A Hawaiian commercial cultivar with a spreading habit.

    Origin: Hawaii

Pests and diseases to watch for

  • Scale insects

    Small bumps, waxy or shell-like, on stems and leaf veins; sticky honeydew and black sooty mold below.

    What to do: Scrub small colonies off with a soft brush.

  • Mealybugs

    White cottony clusters in leaf joints, under leaves and on fruit stems; honeydew and sooty mold.

    What to do: Blast off with a strong spray of water.

  • Aphids

    Clusters of tiny soft insects on new shoots; leaves curl and get sticky.

    What to do: Spray off with water.

  • Sooty mold

    Black, papery film on leaves and fruit that wipes off; it grows on honeydew.

    What to do: Control the insects making honeydew; the mold then weathers away.

  • Spider mites

    Fine pale speckling on leaves, dusty undersides and fine webbing; leaves bronze and drop.

    What to do: Hose the undersides of leaves.

Growing macadamias? Let Gardyn keep track.

Gardyn tells you when your macadamia needs water based on your local weather, reminds you to feed and prune in season, and keeps every harvest and photo.

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General guidance, not medical or veterinary advice. Poison Control (US): 1-800-222-1222. ASPCA Animal Poison Control: (888) 426-4435.