Tree · Proteaceae
Macadamia
Macadamia integrifolia
Give it warmth, deep soil, and a pollination partner, and the macadamia pays you back with rich, buttery nuts.
Full sun
Every 7–14 days
USDA 9–11
30–50 ft · 9.1–15.2 m
Overview
Few trees reward a warm garden like the macadamia. This large evergreen from the Proteaceae family hails from the subtropical forests of southeast Queensland, and it grows into a broad, heavy-canopied beauty of 30 to 50 feet (9 to 15 m). Through winter and spring it throws out long racemes of white to pinkish bloom, then hands over hard-shelled nuts that ripen and drop from late summer into winter.
Plant it where it can bask, on warm, frost-free ground in USDA zones 9 to 11. It craves full sun, digs into deep and rich acidic soil, and drinks at least 50 inches of rain or irrigation across the year. Here is the fun quirk that sets it apart from most fruit trees: as a Proteaceae, it wants very little phosphorus, so easing off the heavy feeding actually helps it thrive.
Growing macadamias runs on patience, and the payoff makes it worth every season. A grafted tree gets cracking and bears in about 2 to 5 years, and most cultivars really take off once a second compatible partner stands nearby to help set the crop. Stick with it and a backyard supply of one of the richest nuts around is yours. One thing every dog owner must lock in first: the nuts are dangerous to dogs.
Care
The short version: hand this tree full sun, a deep bed of rich acidic soil, and a frost-free spot shielded from hard wind. Water it steadily, feed it sparingly with a low-phosphorus mix, and station a second cultivar close by so the flowers turn into a real nut crop.
Light
Macadamias crop hardest in full sun, though they shrug off a little partial sun without complaint. The more light the canopy soaks up, the more flowers and nuts it powers out.
Water
Keep the tree in consistent moisture and plan on at least 50 inches of rain or irrigation a year. Soak it deeply during dry spells, every 7 to 14 days. An established tree brushes off some drought, but nut set and quality nosedive the moment it goes thirsty.
Soil
Get it into deep, rich, well-drained acidic loam at a pH of 5.0 to 6.5. Depth counts as much as fertility, because this big tree drives down a serious root system.
Temperature
The tree loves subtropical warmth and powers along between about 32°F and 95°F (0°C to 35°C). Frost knocks it back, and long spells above the top of that range scorch the leaves and stall the nuts.
Humidity
Average humidity of 50% to 70% hits the sweet spot. Damp, still air at bloom invites blossom blight, so keeping the canopy airy counts for even more than the number.
Feeding
Feed it through spring and summer while it is charging into active growth, but grab a balanced blend low in phosphorus. As a Proteaceae, macadamia is sensitive to phosphorus, and too much yellows the new leaves and kills the tips.
Pruning
Train a young tree to a single central leader and clear out low, crossing, or dead branches in late winter. Once it matures, it asks for only light corrective cuts.
Repotting
This tree belongs in the ground, so repotting barely registers. Pot up a young grafted tree only until it heads out to the field, then plant it out and let it run.
Size & spacing
360–600 in (914–1524 cm) tall
When to plant
Macadamias thrive on warmth and refuse frost outright, so lean into the calendar. Get a grafted tree into the ground in spring once the cold clears out, watch for those fragrant flowers through winter and spring, and gather the nuts as they ripen and tumble down from late summer into winter.
Northern hemisphere
Southern hemisphere
Typical months for a temperate climate: start earlier in warm zones, later where spring frosts linger.
- Sow: Late winter to spring if growing from seed, though grafted trees are strongly preferred
- Plant: Spring, after all danger of frost has passed
- Harvest: Fragrant white to pinkish flowers on long racemes in winter to spring; nuts ripen and drop from late summer through winter
Hardiness
USDA hardiness zones: 9–11
Temperature: down to -7°C
Troubleshooting
Macadamia trouble almost always turns up in the leaves, the flowers, or the nut crop, and it traces straight back to feeding, weather, or a missing pollination partner. Spot what you see below and jump on it early. Nail the basics on a young tree and the rest rarely gets a foothold.
New leaves yellow with dying tips
New leaves that yellow with dying tips flag excess phosphorus, which macadamias and the rest of the Proteaceae just cannot process like other plants. A soil or leaf test nails it down. Cut the high-phosphorus feed, switch to a balanced low-phosphorus blend, and flush the soil with deep watering if the level runs high, and the fresh growth bounces back.
Fix:
- Stop applying high-phosphorus fertilizer
- Switch to a balanced, low-phosphorus fertilizer
- Leach the soil with deep watering if phosphorus is excessive
Nuts tumble off early and hardly any stick
A tree that blooms big but keeps almost nothing usually stands alone or belongs to a self-sterile cultivar, and poor cross-pollination is the driver. Heat above 95°F (35°C) during flowering and nut fill piles on. Plant a second compatible cultivar nearby, keep bees buzzing through the flowers, and hold steady moisture with wind shelter while the nuts fill out.
Fix:
- Plant a second compatible cultivar nearby
- Support bee activity for pollination
- Provide steady moisture and wind protection during nut development
Flower racemes brown and collapse
Blossom blight is a fungus that pounces when the air stays humid and the flowers stay wet. The long racemes discolor and fall apart in muggy weather. Open the canopy with smart spacing and pruning, and spray an approved fungicide at bloom if it keeps charging back year after year.
Fix:
- Improve air circulation through proper spacing and pruning
- Apply an approved fungicide at bloom if blight is recurrent
Burnt edges on sun- and wind-hit leaves
Long heat above 95°F (35°C) and hot, drying winds scorch the leaf margins, and the burn lands hardest on the most exposed foliage. Throw up a windbreak or shelter belt and keep the soil moist through the heat. Pick a frost-free spot that does not bake and this problem stays firmly in check.
Fix:
- Provide wind protection or shelter belts
- Maintain soil moisture during heat
- Site in a frost-free but not excessively hot location
Toxicity
The kernel is a fantastic snack for people, so dig in. Dogs are the catch, and it is a serious one: even a few macadamias can leave a dog weak, shaky, and unable to stand within hours, and the reason still stumps the experts. Keep every nut, raw or roasted or fallen on the ground, well out of a dog's reach.
Toxic to
Cats · Dogs · Horses · Rabbits · Livestock · Birds
Safe for
People
Cats Caution
Cats have no recorded poisoning, but the nut is not proven safe for them either. Keep it off-limits and ring a vet fast if a cat gets one down.
Dogs Severe
This is the big danger. Even a few nuts can leave a dog weak in the hind legs and unable to walk, plus vomiting, a high fever, muscle tremors, an unsteady wobble, and a flattened mood, usually within 12 hours.
Horses Caution
Nobody has studied macadamia toxicity in horses, so keep the nuts and any windfall out of reach until the science catches up.
Rabbits Caution
There is no record of how rabbits handle it, and a rich, fatty nut suits them poorly anyway, so skip it entirely.
Livestock Caution
Cattle, goats, and sheep have not been tested for this toxin, so fence them off from a fruiting tree so they cannot graze on dropped nuts.
Birds Caution
The effect on birds is unknown, and the high fat content does them no favors, so keep the nuts clear of poultry and pet birds alike.
People Edible
Great news for the people around the table: the roasted kernel is a popular snack and perfectly safe to eat. The toxin only hits dogs, not the humans sharing the house.
Keep fallen nuts, raw or roasted nuts, and any nut-containing foods away from dogs; even small amounts can trigger signs.
Helpline numbers
United States
ASPCA Animal Poison Control: (888) 426-4435 (fee applies)
United Kingdom
Animal PoisonLine: 01202 509000 (fee applies)
Australia
Animal Poisons Helpline: 1300 869 738
Varieties
It all boils down to two species and the exciting hybrids and cultivars bred from them. Get to know these names before you plant.
Smooth-shell (Macadamia integrifolia)
It sports a smooth, rounded shell and leads as the main commercial type grown across Hawaii.
Rough-shell (Macadamia tetraphylla)
A separate species flaunting a pebbled, rough shell and often pink new growth, prized as a parent in several hybrids.
'Beaumont'
A pink-flowered cross of integrifolia and tetraphylla that has rocketed to favorite status for backyard plantings.
'Kau' (HAES 344)
A Hawaiian smooth-shell cultivar the University of Hawaii picked out for its high yield and top kernel quality.
Companions
What grows around a macadamia matters less than what grows beside it. A second cultivar is the partner that counts, while thirsty turf under the canopy only gets in the way.
Plant near
second compatible macadamia cultivar: Cross-pollination between cultivars improves nut set and yield.
Keep apart
shallow-rooted turf grass under the canopy: Competes for surface moisture and nutrients and complicates harvesting fallen nuts.
How to propagate
Two routes start a macadamia, and only one delivers reliable nuts. Grafting is how orchards crank out true-to-type trees; seed is the play for rootstock, breeding, and anyone happy to wait.
GraftingModerate
Warm months once seedling rootstocks are about pencil thick · Grafts take in a few months; trees begin bearing in about 2-5 years
Grafting is the winner, because it churns out trees true to the cultivar. Do the work in the warm months once your seedling rootstocks hit pencil thickness, and the graft knits within a few months while the tree charges into bearing in about 2 to 5 years. Match scion to rootstock with care, and never cross a smooth-shell with a rough-shell type by mistake.
SeedModerate
Sow fresh, mature nuts in late winter to spring · Germinates in 1-2 months; seedlings may take 7-12 years to fruit and are variable
Growing from seed is the play for rootstock or breeding, not for dependable nuts. Sow fresh, mature nuts in late winter to spring and they pop up in 1 to 2 months. The catch is patience and luck, since seedlings vary and can take 7 to 12 years to fruit.
Myths
Just a handful of macadamia nuts won't hurt a dog.
Even a small handful can trigger macadamia poisoning, with signs showing up inside 12 hours. Any amount is a vet call, not a wait-and-see.
One lone macadamia tree cranks out a full crop all by itself.
Cultivars run the whole spread from self-fertile to nearly self-sterile, so one tree is a gamble. Planting a second compatible cultivar drives up both nut set and yield, which is exactly why orchards never bank on a single tree.
Macadamias started from seed copy the parent tree and race into fruit.
Seedlings are a roll of the dice and can take 7 to 12 years to bear. Orchards plant grafted trees instead, since those stay true to the cultivar and get fruiting in about 2 to 5 years.