Trident maple bonsai

Placement

Trident maple is an outdoor bonsai. It likes a sunny, airy spot: the more sun it gets, the smaller its leaves stay. During the hottest weeks of summer, however, shield it from the scorching afternoon sun, which can burn the foliage.

Winter is the tricky time. Its roots hold a lot of water and are sensitive to frost, and a frozen root ball can kill the tree, even though the species is very hardy in the ground. Do not expose it to temperatures below 23 °F. Once frosts become harder, move it into a frost-free greenhouse or a cold room, then bring it back out in spring.

Soil mix

Use a very free-draining mix with a pH between 5 and 7. For deciduous trees, a classic blend combines one half akadama, which holds water, one quarter pumice, which gives structure, and one quarter lava rock, which provides aeration and drainage. Sift the akadama to remove dust: it breaks down after about two years, which calls for regular repotting.

Adjust these proportions to your situation: add a little more akadama if you cannot check the tree several times a day in summer, and more lava rock or grit if you live in a wet climate.

Watering

Trident maple grows fast and drinks a lot during the growing season. Water in time, as soon as the surface of the mix starts to dry, but never leave it soggy: excess water rots the roots. Do not water on fixed days; check the mix with a finger, especially in hot weather. Slightly wilted leaves signal thirst, and the tree usually recovers quickly after watering. In winter, keep the root ball moist but never wet.

Rainwater is best: frequent watering with hard water causes chlorosis, with leaves turning yellow.

Fertilizer: during the growing season, apply solid organic fertilizer once a month or liquid fertilizer every week. Pour liquid fertilizer onto the mix, never over the leaves, which it can burn. The more the tree is fed, the more it grows, and the more pinching it needs.

Pruning

In spring, let new shoots develop several pairs of leaves, then shorten them to a single pair. The top grows more strongly than the lower branches: prune it harder so the weaker branches can catch up. New shoots appear all season long and need cutting back as they come. On a mature tree, pinch them very early to keep the fine outer twigs from thickening.

Make large cuts on branches or the trunk in summer, when wounds start healing right away; a vigorous tree can close even large wounds within a few years. Always seal cuts with wound paste to keep fungi, including verticillium, from getting in.

A healthy, compact tree can be partly or fully defoliated in summer, even several times a year where the warm season is long. Defoliation refines ramification, reduces leaf size and keeps inner twigs from dying for lack of light. Cut the leaves but leave the leaf stalks. Never defoliate a weak or freshly repotted tree; full defoliation should not be repeated every year, and it is safer to start by removing a third to half of the largest leaves. After partial defoliation, keep the tree in partial shade for about a month. The largest leaves can be removed at any time.

In fall, as the leaves drop, shorten the twigs, remove those that grow crooked and keep only two twigs at each point. Winter buds are tiny: a magnifying glass helps you see which way they point so you can cut above a well-placed bud.

Wiring

Young branches and twigs wire well during winter dormancy, when bare wood makes the structure easy to see. Use aluminum wire, which suits deciduous trees, about a third as thick as the branch and coiled at roughly 45°. The branches are rather brittle: bend them gradually and protect the bark.

Watch the wire closely: growth is so strong that it can scar the bark very soon after the spring shoots emerge. Remove it by cutting it at every turn rather than unwinding it. To lower an old branch that is too stiff, use a guy wire instead, anchored to a sturdy root or to the pot, with padding under the wire.

Trident maple lends itself to many styles, especially root-over-rock, thanks to its thick, gnarled roots.

Repotting

Repot every two or three years in early spring, just before the buds open; young trees can need it every year, old specimens much less often. The roots grow vigorously and tolerate hard pruning. Remove any that died back over winter.

The tree can be propagated from seed, cuttings or air layers, which root easily. It is rarely sick. Aphids, scale, caterpillars or spider mites occasionally appear, as do powdery mildew and leaf spots: treat with a suitable product, avoiding insecticidal soaps, which are said to harm this species. Overwatering leads to root rot.