Tree · Proteaceae
Macadamia
Macadamia integrifolia
With warmth, deep soil, and a pollination partner, your macadamia will reward a little patience with rich, buttery nuts.
Full sun
Every 7–14 days
USDA 9–11
30–50 ft · 9.1–15.2 m
Overview
If you have room and a warm corner, the macadamia is a wonderful tree to fall for. It is a large evergreen from the Proteaceae family, and its home is the mild subtropical forest of southeast Queensland. Give it time and it settles into a broad, generous shape of 30 to 50 feet (9 to 15 m), hanging out long trusses of white to pinkish bloom through winter and spring before the hard-shelled nuts ripen and drop from late summer into winter.
Do not let the word demanding scare you off. What this tree really asks for is warmth and steady care in USDA zones 9 to 11, full sun, deep rich acidic soil, and a reliable drink of at least 50 inches of rain or watering across the year. There is one habit worth learning early: as a Proteaceae, it dislikes much phosphorus, so the heavy feeding that suits most trees would set it back. Skip that, and you have already avoided the biggest mistake.
Growing macadamias is a slow, rewarding friendship rather than a quick project. A grafted tree needs about 2 to 5 years to start bearing, and most cultivars are happiest with a second compatible partner close by so the flowers set a proper crop. Stick with it and you get a backyard supply of one of the richest nuts around. One caring note if you share your home with a dog: those nuts are genuinely harmful to them, so keep them out of reach.
Care
The short version: give it full sun, deep rich acidic soil, and a frost-free spot sheltered from strong wind. Keep the tree evenly watered, feed lightly with a low-phosphorus blend, and pop a second cultivar nearby so the flowers can actually set nuts.
Light
Your macadamia will crop best in full sun, though it forgives a little partial sun without any fuss. The more light the canopy soaks up, the more flowers and nuts it can hold for you.
Water
Give the tree consistent moisture and plan on at least 50 inches of rain or watering a year. Water deeply during dry spells, every 7 to 14 days, and it will thank you. An established tree copes with some drought, but nut set and quality slip the moment it goes thirsty, so try to keep it comfortable.
Soil
Plant into deep, rich, well-drained acidic loam at a pH of 5.0 to 6.5. Depth matters just as much as fertility here, because this is a big tree that sends down a substantial root system in time.
Temperature
The tree is happiest in gentle subtropical warmth and holds up between about 32°F and 95°F (0°C to 35°C). Frost will hurt it and long spells above the top of that range scorch the leaves and stall the nuts, so a kind, sheltered spot goes a long way.
Humidity
Average humidity of 50% to 70% suits it nicely. Damp, still air during bloom can invite blossom blight, so a bit of gentle airflow through the canopy helps more than the number itself.
Feeding
Feed through spring and summer while the tree is growing, but reach for a balanced blend that is low in phosphorus. As a Proteaceae, macadamia is sensitive to phosphorus, and too much will yellow the new leaves and kill the tips, so a light touch keeps it happy.
Pruning
Train a young tree to a single central leader and clear away low, crossing, or dead branches in late winter. Once it matures it asks for only light corrective cuts, which makes it lovely and low-effort.
Repotting
This is a tree for the open ground, so repotting barely comes up. Pot up a young grafted tree only until it is ready for the field, then plant it out and simply let it grow.
Size & spacing
360–600 in (914–1524 cm) tall
When to plant
Macadamias love warmth and simply cannot handle frost, so timing is your friend here. Set a grafted tree out in spring once the cold has truly gone, enjoy the fragrant flowers that arrive through winter and spring, and gather the nuts gently as they ripen and fall 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
Most hiccups with a macadamia turn up in the leaves, the flowers, or the nut crop, and the reason is nearly always feeding, weather, or a missing pollination partner. Take a calm look at what you are seeing below and step in early. A young tree that gets the basics right usually sails past everything else, so try not to worry.
New leaves yellow with dying tips
When the young leaves pale and the tips die back, the likely reason is excess phosphorus, something macadamias and the wider Proteaceae family cannot process the way other plants do. A quick soil or leaf test will confirm it, so do not guess. Ease off the high-phosphorus feed, move to a balanced low-phosphorus blend, and flush the soil with deep watering if the level is high, and the new growth should recover.
Fix:
- Stop applying high-phosphorus fertilizer
- Switch to a balanced, low-phosphorus fertilizer
- Leach the soil with deep watering if phosphorus is excessive
Early nut drop leaves the tree nearly bare
If your tree blooms beautifully yet keeps almost nothing, a lone tree or a self-sterile cultivar is usually behind it. Poor cross-pollination is the main cause, and heat above 95°F (35°C) during flowering and nut fill makes matters harder. Plant a second compatible cultivar nearby, keep bees busy at the flowers, and hold steady moisture with a little wind shelter while the nuts develop, and you will see a real difference.
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 moves in when the air stays humid and the flowers stay wet. You will notice the long racemes discolor and fall apart in muggy weather, which is disheartening but manageable. Open the canopy with sensible spacing and pruning, and spray an approved fungicide at bloom if it keeps returning 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 damage tends to show worst on the most exposed foliage. Put up a windbreak or shelter belt and keep the soil moist through the heat, and the tree copes far better. Choosing a frost-free spot that does not bake in the sun keeps this in check for good.
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 lovely snack for people, so enjoy it freely. For dogs it is a different story, and this is the part to take seriously: even a few macadamias can leave a dog weak, shaky, and unable to stand within hours, and researchers still do not know why. Keep every nut, raw or roasted or fallen on the ground, safely out of a dog's reach.
Toxic to
Cats · Dogs · Horses · Rabbits · Livestock · Birds
Safe for
People
Cats Caution
No poisoning has ever been recorded in cats, though that does not make the nut proven safe for them. Treat it as off-limits and phone a vet if a cat manages to eat one.
Dogs Severe
This is where real care is needed. Even a few nuts can leave a dog weak in the hind legs and unable to walk, and bring on vomiting, a high fever, muscle tremors, an unsteady wobble, and a flattened mood, usually within 12 hours.
Horses Caution
Macadamia toxicity has not been studied in horses, so the nuts and any windfall are best kept well out of reach until more is known.
Rabbits Caution
There is no record of how rabbits react, and a rich, fatty nut suits them poorly in any case. It is kindest not to offer it.
Livestock Caution
Cattle, goats, and sheep have not been tested for this toxin. Fence them away from a fruiting tree so they cannot graze on dropped nuts.
Birds Caution
Nobody knows yet how birds respond to this toxin, and such a rich, fatty food is not kind to them anyway, so it is safest to keep every nut well away from chickens and pet birds.
People Edible
Good news for the people in the house: the roasted kernel is a popular snack and perfectly safe to eat. The toxin only troubles dogs, not the humans sharing the table.
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
Macadamia really comes down to two species and the friendly hybrids and cultivars bred from them. These are the names it helps to know before you choose your tree.
Smooth-shell (Macadamia integrifolia)
It wears a smooth, rounded shell and is the main commercial type grown throughout Hawaii.
Rough-shell (Macadamia tetraphylla)
This is a separate species with a pebbled, rough shell and often pink new growth, and it is prized as a parent in several hybrids.
'Beaumont'
A pink-flowered cross of integrifolia and tetraphylla that has become a much-loved choice for backyard plantings.
'Kau' (HAES 344)
A Hawaiian smooth-shell cultivar the University of Hawaii chose for its generous yield and lovely 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
There are two gentle ways to begin a macadamia, and only one gives you dependable nuts. Grafting is how the orchards do it and what will serve you best, while seed is really for rootstock, breeding, and anyone with plenty of time to spare.
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 route to take, because it gives you trees that stay true to the cultivar. Do the work in the warm months once your seedling rootstocks reach pencil thickness, and the graft knits within a few months while the tree comes into bearing in about 2 to 5 years. Match scion to rootstock with care, and take care never to 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 really for rootstock or breeding rather than dependable nuts, so go in with open eyes. Sow fresh, mature nuts in late winter to spring and they sprout in 1 to 2 months. The catch is patience and a little luck, since seedlings vary and can take 7 to 12 years to fruit.
Myths
Dogs can safely eat a small number of macadamia nuts.
Even a small handful can set off macadamia poisoning, with signs appearing inside 12 hours. Any amount is a vet call, not a wait-and-see, so treat every nut as one to keep away from your dog.
One macadamia tree is enough to give you a full harvest.
Cultivars range from self-fertile all the way to nearly self-sterile, so one tree is a gamble. Planting a second compatible cultivar lifts both nut set and yield, which is exactly why orchards never lean on a single tree.
Macadamias raised from seed match their parent and begin bearing quickly.
Seedlings are unpredictable and can take 7 to 12 years to bear. Orchards plant grafted trees instead, since those stay true to the cultivar and begin fruiting in about 2 to 5 years, which is a far kinder wait.