Seasonal Care Guide

Spring is the most important and most active period in the bonsai calendar. As temperatures rise and daylight hours increase, your trees will break dormancy and begin pushing new growth. Watch for buds swelling on deciduous species from late February onward, depending on the weather.

Watering needs increase rapidly during this period. A tree that needed water once every few days in winter may need daily watering by late April. Don't water on a fixed schedule. Check the soil surface every day and water thoroughly when the top centimetre feels dry. Water until it runs freely from the drainage holes, then move on. Underwatering in spring, when the tree is investing energy in new growth, can set a tree back badly.

Repotting is best done in early to mid spring, just as buds are beginning to swell but before new growth has fully extended. This is when root growth is about to kick in, so the tree can recover quickly and establish itself in fresh soil. For most species in the UK, that window is roughly mid-March to mid-April. Use a well-draining bonsai soil mix (akadama, pumice, and lava rock in roughly equal parts works well for most species). Trim back the root mass by about a third, removing any circling roots and dead material.

Begin feeding once you see new growth actively extending. A balanced fertiliser (equal nitrogen, phosphorus, and potassium) applied every two weeks is a good starting point. Organic solid fertilisers like Biogold or rapeseed cake are popular because they release slowly and are hard to overdo.

Keep a close eye on late frosts. Even hardy species can be damaged if caught with fresh, soft new growth exposed to a sharp overnight frost. If frost is forecast and your trees have already pushed new growth, move them somewhere sheltered overnight or cover them with fleece.

Summer care is dominated by watering. On hot, sunny days, outdoor bonsai in small pots can dry out alarmingly fast. Check the soil twice a day in hot weather: once in the morning and again in the late afternoon. Water thoroughly whenever the surface is dry. Don't just give a light sprinkle that wets the top layer and misses the roots below. The whole root mass needs soaking.

If you're going away for a few days and can't arrange someone to water, move your trees into full shade (which slows water loss), group them together, and water them very thoroughly before you leave. Capillary matting or self-watering trays can buy you an extra day or two, but they're not a long-term substitute for proper watering.

Deciduous trees in full leaf can be defoliated in early summer (late May to mid-June) to encourage a second flush of smaller, more refined leaves. Only defoliate healthy, vigorous trees that have been well-fed. The tree responds to losing all its leaves by pushing a new set, and these second-flush leaves come in smaller and with shorter internodes, which improves the overall refinement. Don't defoliate conifers, weak trees, or trees that were repotted the same year.

Continue feeding through summer, though you can reduce the frequency slightly during the hottest weeks if growth slows. Some growers switch to a lower-nitrogen feed in mid to late summer to avoid pushing too much soft growth heading into autumn.

Pest vigilance is important in summer. Aphids, spider mites, and scale insects are all active. Check the undersides of leaves regularly. A strong jet of water will dislodge aphids, and neem oil spray handles most common pests without harming the tree. Act quickly, because infestations spread fast in warm weather.

Protect trees from extreme heat. Afternoon sun in July and August can scorch leaves, especially on Japanese Maples and other thin-leaved species. Move vulnerable trees into dappled shade during heatwaves, or use shade cloth over your bench.

Autumn is a transitional period. Growth is slowing, and the tree is beginning to prepare for dormancy. Your job is to help it harden off and go into winter in the best possible condition.

Reduce feeding or switch to a low-nitrogen fertiliser (something with a higher ratio of phosphorus and potassium, like a 0-10-10 formula). Nitrogen promotes leafy growth, which you don't want heading into winter because soft new growth is vulnerable to frost damage. Phosphorus and potassium support root strength and overall hardiness.

Watering needs decrease as temperatures drop and days shorten, but don't stop paying attention. Autumn can be wet in the UK, which means your trees may need less supplementary watering, but they can also sit in waterlogged soil if drainage is poor. Make sure pots are draining freely and that saucers aren't collecting standing water.

This is an excellent time for structural pruning on deciduous trees. Once the leaves have dropped (usually by mid to late November in the Midlands), you can see the branch structure clearly for the first time since spring. Remove any branches that cross, grow directly upward or downward against the design, or are too thick relative to their position. The tree will heal pruning wounds more slowly while dormant, but there's no sap flow to worry about and no risk of die-back running into actively growing tissue.

Enjoy the autumn colour. Maples and other deciduous species put on a real show in October, and it's worth taking a moment to photograph your trees at their best. The colours can shift from day to day.

Start planning your winter protection. If you have any trees that are borderline hardy (Chinese Elm, Serissa, some Ficus), think about where they'll go once temperatures drop below freezing regularly.

Winter is the quiet season, but it's not a time to forget about your trees. Hardy species like Juniper, Pine, Maple, and native deciduous trees need a period of cold dormancy to stay healthy over the long term. Don't bring them indoors where the central heating will disrupt their rest.

The main risk in winter is not cold air but frozen rootballs. In the ground, tree roots are insulated by surrounding earth. In a shallow bonsai pot, they're exposed on all sides. A sustained hard frost can freeze the entire root mass solid, which can kill roots and damage the tree badly. Protect against this by grouping pots together (mass retains heat), placing them on the ground against a sheltered wall, and insulating with straw, bubble wrap around the pots, or burying them up to the rim in mulch. An unheated greenhouse, cold frame, or garage with a window works well for extra protection during severe cold snaps.

Water sparingly but consistently. The tree is dormant, not dead. The soil should never dry out completely, even in winter. Check once a week or so and water lightly if the soil surface is dry. Water on mild days when temperatures are above freezing, ideally in the morning so any excess moisture can drain before nightfall.

Don't prune or wire in the dead of winter unless you need to. Deciduous trees are brittle when dormant and branches are more likely to snap. If you want to do structural work on deciduous trees, late autumn or very early spring is better.

Use the quiet months for planning. Study your trees, look at them from different angles, decide what you want to work on in spring. Read books, watch videos, visit exhibitions. The learning side of bonsai doesn't stop in winter, even if the growing does.