Bonsai Care Guide: How to Keep Your Bonsai Healthy in Melbourne

A bonsai is a normal tree grown in a small pot, so it needs everything a tree needs, just in less soil and with less margin for error. Get light and watering right and most other problems never show up.

Indoor or outdoor: know your tree

The first job is finding out what kind of tree you have, because it decides where it lives.

• Tropical and subtropical trees can live indoors year-round. They don't go dormant and don't like cold below about 10°C.
• Temperate trees (most deciduous trees and conifers) must live outdoors. They need a cold winter rest to stay healthy. Kept inside, they weaken and usually die within a year or two.

If you're not sure, ask us when you buy. We'll tell you which group yours sits in.

Light

More light is almost always better. Low light is the most common reason indoor bonsai decline.

• Indoors: right beside your brightest window, ideally north- or east-facing. A metre back from the glass is a lot less light than it looks.
• Outdoors: morning sun and afternoon shade suits most trees in Melbourne. Protect from harsh afternoon sun on 35°C+ days.
• Turn the pot a quarter every week or two so the tree grows evenly.
• If your space is dim, a plant grow light on for 10–12 hours a day makes a real difference.

Watering

Water when the top centimetre of soil feels just dry, not on a fixed schedule. Small pots dry out fast, so check daily.

1. Push a finger or chopstick into the soil. Damp? Leave it. Just dry? Water.
2. Water slowly until it runs freely out of the drainage holes. Wait a minute and do it again so the whole root ball is soaked.
3. Let the pot drain fully. Never leave it sitting in water.

In a Melbourne summer, outdoor trees may need water once or twice a day. In winter, it might be once a week or less. Both overwatering and drying out completely can kill a bonsai, so it's worth building the daily check into your routine.

Humidity

Indoor trees prefer more humidity than most homes have, especially with heating on. Two things actually help:

• A humidity tray: a shallow tray of pebbles with water just below the top of the stones. Sit the pot on the pebbles, not in the water.
• Grouping plants together, which raises humidity around all of them.

Keep trees away from heaters, air conditioners and draughty doors. Outdoor trees don't need any extra humidity.

Feeding

A bonsai's small pot holds very few nutrients, so regular feeding matters.

• Feed during the growing season, roughly September to April.
• Use a balanced liquid fertiliser at half strength every two weeks, or a slow-release bonsai fertiliser as directed on the pack.
• Ease off in winter. Indoor tropicals can have a feed once a month; outdoor temperate trees need none while dormant.
• Don't feed a tree that's bone dry, sick or freshly repotted. Water first, and wait about a month after repotting.

Pruning and shaping

Regular light trimming keeps the tree compact and its shape tidy.

• Maintenance pruning: once a new shoot has grown 6–8 leaves, cut it back to 2–3. Do this through the growing season.
• Structural pruning (removing larger branches): best done in late winter or early spring, before new growth starts.
• Use sharp, clean scissors or bonsai shears so cuts heal cleanly.
• Wiring can bend branches into shape. Check it every few weeks and remove it before it starts cutting into the bark.

Never take more than about a third of the foliage at once. A stressed tree needs its leaves to recover.

Repotting and soil

Repot in spring, and only when the tree needs it. That's usually every 2–3 years for young trees and 3–5 for older ones.

Signs it's time: roots circling the pot or poking out the drainage holes, or water sitting on top instead of soaking in.

1. Ease the tree out and gently comb out the outer roots.
2. Trim back no more than about a quarter of the root mass.
3. Replant in fresh, free-draining bonsai mix. Never use regular potting soil or garden soil — it holds too much water and rots roots.
4. Water well and keep the tree out of strong sun and wind for 2–3 weeks while it settles.

Avoid repotting in summer, autumn or winter unless the tree is in real trouble, like root rot.

Through the year in Melbourne

Season	What to focus on
Spring (Sep–Nov)	Repot if needed, start feeding, structural pruning before buds open, watch for pests on new growth
Summer (Dec–Feb)	Check water daily (outdoor trees may need it twice), shade from hot afternoons and north winds, keep up light pruning
Autumn (Mar–May)	Taper off feeding, let outdoor deciduous trees colour and drop leaves naturally, no repotting
Winter (Jun–Aug)	Water less, keep indoor trees off cold windowsills at night, shelter outdoor trees from hard frost but leave them outside

Common problems

What you see	Likely cause	What to do
Yellow leaves, soggy soil	Overwatering or poor drainage	Water only when the top is dry; check drainage holes aren't blocked
Crispy brown leaves, dry soil	Underwatering or heat	Soak the root ball fully; move out of hot afternoon sun
Sudden leaf drop indoors	Moved spot, draught, or low light	Keep it in one bright spot away from heaters and doors; it usually regrows
Long, thin, pale shoots	Not enough light	Move closer to a window or add a grow light
Sticky leaves, tiny bugs, webbing	Pests (aphids, scale, spider mite)	Wipe off, then treat with a horticultural oil or insecticidal soap
White crust on soil	Mineral build-up	Flush with plenty of water; refresh soil at next spring repot

Quick reference

• Light: as much as possible
• Water: when the top centimetre is just dry, soak thoroughly
• Humidity: pebble tray and grouping for indoor trees
• Feed: every two weeks, September to April
• Prune: trim shoots back to 2–3 leaves through the growing season
• Repot: spring only, every few years, in bonsai mix