Macadamia (Queensland nut) care

Light

Macadamia needs sun on the leaves, not just bright ambient room light. Full sun for heavy cropping; young trees appreciate light shade or wind shelter. Deep shade reduces flowering and nut yield sharply. A south or west-facing windowsill in the northern hemisphere is the default; anywhere else, expect the plant to stretch and pale out within a season.

Watering

Outdoor macadamia crops want keep evenly moist; deep water weekly in dry spells, more during flowering and nut fill. The single best habit is a finger-test before watering — push a finger 3-4 cm into the soil. Damp = wait a day; dust-dry = water deeply at the base of the plant. Shallow-rooted and intolerant of both drought and waterlogging. Mulch heavily and irrigate consistently through bloom and nut development; never let the root zone dry out completely.

Soil and pot

Macadamia grows best in deep, fertile, well-drained acidic loam, rich in organic matter. Prefers pH 5.0-6.5. The shallow proteoid root system needs friable, free-draining soil and resents heavy clay, alkalinity, and salinity. A pot with a working drainage hole is non-negotiable for this species — even free-draining mix will turn soggy in a closed planter. If you love the look of a decorative pot without a hole, use it as a cachepot around an inner nursery pot you can lift out to water.

Humidity and temperature

Macadamia sits happiest at around 60-80% humidity and 10 to 30°C (50 to 86°F). Native to humid subtropical forest and thrives in moist air. Tolerates lower humidity if irrigated, but hot, dry winds scorch foliage and abort flowers. If you keep the room above 10 to 30°C year-round and avoid placing the plant near a cold draught, a hot radiator, or an air-conditioning vent, you have already handled the two biggest indoor stressors.

Fertilising

Feed macadamia sparingly. Feed little and often with a low-phosphorus fertiliser; Proteaceae are phosphorus-sensitive and high-P feeds cause toxicity. Use balanced, gentle, slow-release products and supplement with potassium during nut fill. Skip fertiliser entirely on a stressed, recently-repotted, or actively wilting plant — fertiliser salts make damage worse, not better. Wait for a round of healthy new growth before resuming a feeding rhythm.

Common problems

Below are the issues we see most often on macadamia in the Growli community. Each is annotated with the most common cause so you know where to start.

• Frost and wind damage — Young trees are killed by frost and the brittle wood snaps in storms. Site in a sheltered, frost-free spot and stake until established.
• Phosphorus toxicity — Standard high-P fertilisers damage the proteoid roots, yellowing and scorching leaves. Always use low-phosphorus feeds formulated for Proteaceae or natives.
• Slow to bear and biennial cropping — Seedlings can take 8-12 years to fruit and crop unevenly; choose grafted cultivars and provide steady moisture and nutrition to even out yield.
• Nut borer and husk spot — Macadamia nut borer and fungal husk spot reduce crops in humid regions. Clear fallen husks, maintain airflow, and monitor for early intervention.

Propagation

Grafted onto seedling rootstock for true-to-type, earlier-bearing trees; this is the standard method. Seed grows readily but is slow to fruit and variable. Cuttings root with difficulty under mist with rooting hormone. Propagation is the cheapest, most satisfying way to expand a collection — and it doubles as insurance against losing a mature plant to an accident. Take a backup cutting once the parent is established and healthy.

Toxicity to pets

Macadamia is toxic to pets. The ASPCA does not individually list Macadamia integrifolia, but macadamia nuts are a well-documented toxin to dogs, recognised by the ASPCA Animal Poison Control Center. Ingestion causes weakness, vomiting, tremors, hyperthermia, and hind-limb ataxia, typically within 12 hours. Treat the tree and its nuts as dog-toxic; keep fallen nuts cleared and contact a vet if a dog ingests any. If you keep cats, dogs, or curious children in the house, weigh placement carefully — a high shelf or a hanging planter is enough for casual safety. For severe ingestion incidents, call your local vet and the ASPCA Animal Poison Control Center (in the US, 888-426-4435).

Pet-safety status is sourced from the ASPCA Toxic and Non-Toxic Plant List, which catalogues the most-asked-about plants for cats, dogs, and horses.

Macadamia deep-dive guides

Every aspect of macadamia care, each with its own calibrated guide:

• Macadamia watering schedule
• Macadamia light requirements
• Best soil mix for macadamia
• Macadamia fertilizing guide
• When to repot macadamia
• How to propagate macadamia
• Macadamia growth rate & size
• Macadamia cold hardiness
• Macadamia temperature & humidity
• Is macadamia toxic to cats & dogs?
• Is macadamia toxic to cats?
• Is macadamia toxic to dogs?

Related guides

Macadamia is also known as macadamia, smooth-shelled macadamia, and Queensland nut.

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