The Bonsai Seasonal Care Calendar: What to Do Every Month
Almost every important bonsai task has a right time and a wrong time, and the difference between them is the difference between a tree that improves each year and one that merely survives. This calendar lays out the year task by task — repotting, pruning, wiring, feeding, pinching and winterising — for deciduous, conifer and tropical trees.
# The Bonsai Seasonal Care Calendar: What to Do Every Month
Almost every important bonsai task has a right time and a wrong time, and the difference between them is the difference between a tree that improves each year and one that merely survives. This calendar lays out the year task by task — repotting, pruning, wiring, feeding, pinching and winterising — for deciduous, conifer and tropical trees.
Before the calendar: three things that change the dates
This calendar is written for the Northern Hemisphere temperate zone. If you are south of the equator, shift everything by six months. If you are in Zone 9 or warmer, expect spring events several weeks earlier and a shorter, less reliable dormancy.
- Your climate. "Early spring" in coastal Georgia is February; in Minnesota it is April. Read the calendar by phase — bud swell, leaf-out, hardening off, dormancy — and let your own trees tell you which phase they are in.
- Your tree type. Deciduous, evergreen conifer, and tropical species follow genuinely different schedules. Where they diverge, this guide says so.
- Tropicals barely follow it at all. Species like Ficus, Fukien Tea and Dwarf Jade never experience a real winter indoors. Their year is governed by light levels, not temperature, so their work window is late spring through summer.
Winter: dormancy and structural work
The temperate trees are asleep. This is the quietest season for the grower and the most dangerous one for the tree, because the risks are invisible: frozen roots, desiccating wind, and pots that dry out unnoticed on a cold sunny day.
December
Complete winter protection. Potted roots are far less hardy than the same species in the ground — the working rule is that a bonsai is effectively one to two zones less hardy than its rating. Move trees into an unheated garage, cold frame or shed, or heel the pots into a mulch bed on the sheltered side of the house.
Water sparingly but never let pots go bone dry. Dormant trees still lose moisture, and desiccation kills more overwintering bonsai than cold does. Check weekly and water when the surface is dry and the temperature is above freezing.
Do not feed. Clear fallen leaves and debris from the soil surface, where fungal spores and overwintering pests shelter.
January
The deep-dormancy month, and the best time of year to look at your trees. With deciduous species bare — Japanese Zelkova, Hornbeam, Trident Maple, European Beech — the branch structure is fully visible. Photograph them, plan next season's cuts, and mark which branches go.
Structural pruning of deciduous trees can be done now: the tree is dormant, there is no leaf mass to obscure the design, and it will heal fast in spring. Wiring conifers is also a winter job — Shimpaku Juniper, Chinese Juniper and Japanese Black Pine are wired while dormant, when branches are less brittle with sap and there is no new foliage in the way.
Order soil components and pots now, before the spring repotting rush.
February
The transition month. Watch for the first buds to swell — that is the starting gun for repotting.
Late February is when early-waking species begin. In milder zones Japanese Apricot and Forsythia are already flowering. Begin easing trees out of the darkest winter storage as hard frosts recede, but keep protection available: a late freeze on trees that have already broken dormancy is one of the worst things that can happen to a collection.
Tropicals in winter: the hardest season indoors. Light is weakest and central heating dries the air. Give the brightest available window, raise humidity with a pebble tray, water less often than in summer, and do not repot or hard-prune. Some leaf drop on a Weeping Fig after moving indoors is normal.
Spring: repotting, then explosive growth
The busiest season. Everything you do now compounds through the rest of the year.
March
The main repotting window. Repot when buds have swollen but not yet opened — the tree is mobilising stored energy and about to push new roots, so recovery is fastest. Young trees every 1-2 years, mature deciduous every 2-3, mature conifers every 3-5.
Remove no more than about a third of the root mass, work fresh soil in with a chopstick so no air pockets remain, anchor the tree firmly, water until it runs clear, then put it in bright shade and do not fertilise until new growth appears.
This is the window for Japanese Maple, Trident Maple, Chinese Elm, Korean Hornbeam, Crabapple and the conifers. Species that flower on old wood — Satsuki Azalea, Japanese Flowering Quince — wait and are repotted after they bloom.
Finish structural pruning before the buds open. Apply dormant oil or fungicide now if you had pest or fungal problems last year.
April
Growth accelerates. Begin feeding trees that were not repotted as soon as the leaves harden; repotted trees wait until new growth is clearly established.
Start pinching and pruning new shoots on vigorous deciduous species to build ramification. On elms and maples, let a new shoot extend to five or six leaves, then cut back to two — repeated through the season, this is what creates fine twigging.
Watch water closely: as leaves expand, water use climbs steeply, and a tree that needed water every other day in March may need it daily by late April. Keep frost protection on standby — tender new growth on a Japanese Maple is easily scorched by a late freeze. Pests wake up now too: inspect leaf undersides weekly for aphids, scale and spider mites.
May
Peak growth. Feed regularly with a balanced fertiliser and continue pinching and directional pruning.
Defoliation, if you use it, happens in late spring on healthy, vigorous deciduous trees only. Removing the leaves of a strong Trident Maple, Chinese Elm or Japanese Zelkova forces a second, finer flush of smaller leaves and increases ramification. Never defoliate a weak tree, a tree repotted this spring, or a conifer.
Candle work on pines runs May into June. On Japanese Black Pine and Japanese Red Pine, decandling — removing the spring candles entirely on strong, healthy trees — triggers a second, shorter flush with shorter needles. On single-flush pines such as Scots Pine, Mugo Pine and Japanese White Pine you do not decandle; you shorten the candles by pinching and balance strength between branches.
Move trees to their summer positions and check wire weekly — spring growth thickens branches fast, and wire left too long scars permanently.
Tropicals in spring: their year begins. Repot now through summer, resume full feeding, and move outdoors once night temperatures reliably stay above about 50F. Acclimatise gradually to avoid leaf scorch.
Summer: maintenance, water, and restraint
Summer is not a building season. It is a holding season: keep the tree healthy, keep it watered, and resist the urge to do major work in the heat.
June
Water becomes the dominant task. In hot weather many trees need water once or twice daily — check every tree individually rather than watering on a schedule, and water thoroughly until it runs from the drainage holes rather than giving frequent shallow sips.
Continue feeding, but reduce nitrogen if you want to slow extension growth on refined trees. Finish pine candle work. Provide afternoon shade for species that resent scorching sun: Japanese Maple in particular will crisp its leaf margins in full afternoon sun in a hot climate, as will European Beech and Flowering Dogwood.
Deadhead spent flowers on Satsuki Azalea and prune it now — its flower buds for next year set in mid-to-late summer, so pruning after roughly early July costs you the display.
July
Peak heat. Minimise stress: no repotting, no defoliation, no hard pruning. Light maintenance trimming only.
Watch for spider mites, which thrive in hot dry conditions — especially on junipers, Cotoneaster and dwarf conifers. Fine stippling on the foliage and faint webbing are the tell-tales, and a hard hose-down of the foliage several times a week is a genuinely effective control.
Drought-adapted species handle this month easily: Olive, Rosemary, Pomegranate and Crepe Myrtle all want heat. Moisture-lovers such as Bald Cypress and Dawn Redwood can stand in a shallow water tray through the hottest weeks.
If you are going away, arrange watering. A week unattended in July will kill trees that would shrug off the same neglect in October.
August
Heat continues but growth begins to slow. Shift fertiliser toward lower nitrogen and higher potassium to harden off the season's growth ahead of winter — soft, sappy late growth is what gets damaged by the first frosts.
Late August is a reasonable time to begin autumn wiring on deciduous species as growth firms up. Check every wire again: anything applied in spring is likely due to come off.
Tropicals in summer: their strongest growth. Feed heavily, prune and wire freely, and repot if needed. Outdoors they will grow several times faster than they ever will indoors.
Autumn: colour, hardening, and preparation
September
Growth slows and the tree begins moving resources into storage. Reduce or stop nitrogen feeding on temperate species; many growers give a final low-nitrogen feed early in the month and then stop.
This is a good window for wiring deciduous trees — the branches are lignified but still flexible, and once the leaves drop you can see exactly what you are doing.
Reduce watering frequency as temperatures fall and daylight shortens. Overwatering in autumn is a common and avoidable cause of root problems.
October
Autumn colour arrives. This is the payoff month for Japanese Maple, Trident Maple, Ginkgo, Sweetgum, Japanese Larch and Dawn Redwood — the last two being deciduous conifers that turn gold and drop their needles. Berrying species come into their own too: Pyracantha, Cotoneaster, Winterberry Holly and Beautyberry.
Bring tropicals back indoors before night temperatures drop below about 50F. Inspect thoroughly for pests first — bringing scale or mites into a warm house in October means fighting them all winter.
Begin preparing winter protection: clean out the cold frame, source mulch, and decide where each tree will spend the winter.
November
Leaf drop finishes. Clear all fallen leaves from the soil surface and the bench, since leaf litter harbours fungal spores and overwintering insects.
Apply winter protection as hard frosts arrive. The goal is not to keep trees warm — most temperate species genuinely need cold dormancy and perform poorly without it — but to keep the roots from freezing solid and to shield the tree from drying wind and winter sun.
Cold-hardy species make this easy: Japanese Larch, Norway Spruce, White Spruce, Mugo Pine and Scots Pine want a real winter and need only root insulation. Species marginal for your zone need more shelter.
Reduce watering to a weekly check. Take a final round of photographs — the bare structure in late autumn is the honest record of what you actually built this year.
Tropicals in autumn: move back indoors, reduce feeding and watering as light drops, and stop major work.
The year in one page
- Winter. Deciduous: structural prune, plan, protect roots. Conifers: wire, protect roots. Tropicals: maximum light, minimal water, no work.
- Spring. Deciduous: repot at bud swell, feed, pinch, defoliate late. Conifers: repot at bud swell, candle work in May and June. Tropicals: repot, resume feeding, move outdoors.
- Summer. Deciduous: water hard, light trim only, shade sensitive species. Conifers: water, watch for mites, finish candle work. Tropicals: peak growth — feed, prune and wire freely.
- Autumn. Deciduous and conifers: wire, low-nitrogen feed then stop, enjoy the colour. Tropicals: return indoors before 50F nights.
Make it specific to your trees
A calendar is a framework; your particular species and climate fill in the dates. Every care sheet in the species library lists the hardiness range, water preference and pruning window for that tree — and if you create a free account and save your collection, the site will send you seasonal reminders timed to the species you actually own rather than a generic schedule.