Fertilising guide
How to fertilise Kauri (Agathis australis)— schedule & NPK
Also called Kauri, New Zealand Kauri.
More about kauri
About Kauri
Agathis australis · also called Kauri, New Zealand Kauri · flowering
Kauri is one of the world's most impressive and ancient conifers, native to the warm-temperate forests of New Zealand's Northland. It produces a massive straight trunk with smooth, grey-brown flaking bark and leathery, strap-like leaves. It demands frost-free conditions and is grown in temperate climates only under glass. Sacred to Maori culture and critically threatened in the wild by kauri dieback disease.
Growth habit: Broadly conical when young, developing a massive straight cylindrical trunk with a high domed canopy of spreading branches; trunk clear of branches for much of its height at maturity
What fertiliser kauri actually wants — and why
Kauri is an easy, light foliage feeder — a half-strength balanced liquid feed through the growing months keeps it green without forcing weak, sappy growth.
A balanced general houseplant feed (roughly even N-P-K) is exactly right — it is grown for foliage, so steady, moderate nitrogen for healthy leaves is the goal, not a bloom or root formula.
For the language behind the three numbers on the bottle — what nitrogen, phosphorus and potassium each do — see the NPK ratio explained entry. The short version for kauri: match the feed to the job the plant is doing right now, not to a generic “plant food” on the shelf.
How often to feed kauri, and which months
Feeding only earns its keep while the plant is in active growth and can use the nutrients — pour feed into a dormant or low-light plant and it simply builds up as root-burning salt. For kauri:
Apply a balanced, low-phosphorus liquid fertiliser at half strength monthly during the growing season (spring through summer). Kauri is adapted to low-nutrient soils; excess fertiliser, especially phosphorus, can damage mycorrhizal associations and cause root toxicity. Do not feed in autumn or winter. Treat that as monthly between spring through early autumn (roughly March to September); ease off in autumn and stop entirely in the low light of winter.
The dormant-season rule matters more than the exact interval: skip feeding entirely when kauri is resting. For the wider context on indoor feeding rhythms across the seasons, the houseplant fertiliser schedule walks through the year month by month.
What strength to mix for kauri
Half strength is the safe default for kauri — houseplant feeds are formulated strong, and the diluted dose is gentler on the roots while still ample for foliage.
Feeding always goes onto already-damp soil, never dry roots — water kauri first if the soil is dry, then apply the diluted feed. The companion question is when to water at all, covered in the kauri watering schedule.
Signs you are over-feeding kauri
Over-feeding is far more common — and more damaging — than under-feeding for most plants. The classic tells for kauri:
- Brown, crispy leaf tips and edges with no sign of underwatering.
- A white, crusty salt deposit on the soil surface or pot rim.
- Weak, pale, stretched new growth that flops.
- Lower leaves yellow and drop while the soil is correctly watered.
Signs you are under-feeding kauri
- Uniformly pale or yellow-green leaves, oldest first.
- Noticeably small new leaves and stalled growth in good light and season.
- A generally tired, lacklustre look despite correct watering and light.
If the symptoms point at watering, light or roots rather than nutrition, the full kauri care brief covers soil, humidity and the common problems for this species.
Flushing and leaching the salts
Flush the pot of kauri with plain water until it runs freely from the base every couple of months in the feeding season — it washes out the fertiliser salts that cause brown tips.
Organic vs synthetic feeds for kauri
Organic options
A diluted seaweed or worm-casting feed, or fish emulsion if you can tolerate the smell indoors. UK: Westland or Baby Bio Organic, dilute seaweed; US: Espoma Indoor! or Neptune's Harvest fish & seaweed. Slow, gentle and hard to overdo.
Synthetic / liquid feeds
A general-purpose houseplant liquid at half strength — UK: Baby Bio, Westland Houseplant Feed or Phostrogen; US: Miracle-Gro Indoor Plant Food or Schultz. Convenient and fast-acting; the only risk is overdoing it.
Brand names are examples, not endorsements, and UK and US ranges differ — check the label’s own NPK and dilution rate, since formulations change.
Fertilising kauri — frequently asked questions
What fertiliser does kauri need?
A balanced general houseplant feed (roughly even N-P-K) is exactly right — it is grown for foliage, so steady, moderate nitrogen for healthy leaves is the goal, not a bloom or root formula. Kauri is an easy, light foliage feeder — a half-strength balanced liquid feed through the growing months keeps it green without forcing weak, sappy growth.
How often should I feed kauri?
Apply a balanced, low-phosphorus liquid fertiliser at half strength monthly during the growing season (spring through summer). Kauri is adapted to low-nutrient soils; excess fertiliser, especially phosphorus, can damage mycorrhizal associations and cause root toxicity. Do not feed in autumn or winter. Apply a balanced, low-phosphorus liquid fertiliser at half strength monthly during the growing season (spring through summer). Kauri is adapted to low-nutrient soils; excess fertiliser, especially phosphorus, can damage mycorrhizal associations and cause root toxicity. Do not feed in autumn or winter. Treat that as monthly between spring through early autumn (roughly March to September); ease off in autumn and stop entirely in the low light of winter.
What strength of feed for kauri?
Half strength is the safe default for kauri — houseplant feeds are formulated strong, and the diluted dose is gentler on the roots while still ample for foliage.
What does over-feeding kauri look like?
Brown, crispy leaf tips and edges with no sign of underwatering. A white, crusty salt deposit on the soil surface or pot rim. Weak, pale, stretched new growth that flops. Lower leaves yellow and drop while the soil is correctly watered. Feeding kauri year-round on a fixed schedule, including dark winter months, is the most common mistake — it cannot use the nutrients in low light and the surplus simply burns the roots and crusts the soil.
Should I flush the soil of kauri?
Flush the pot of kauri with plain water until it runs freely from the base every couple of months in the feeding season — it washes out the fertiliser salts that cause brown tips.
Keep reading
- Kauri care — the full brief (light, soil, humidity, problems, pet safety)
- How often to water kauri — the watering schedule
- The houseplant fertiliser schedule — feeding through the year
- NPK ratio explained — what the three numbers on the bottle mean
- How to fertilise cutleaf coneflower
- How to fertilise paprika yarrow
- How to fertilise fernleaf yarrow
- All 6887 fertilising guides in the Growli library