Hinoki cypress bonsai

Placement

Chamaecyparis obtusa is a “false cypress” native to Japan and Taiwan, where it forms trees that can reach 131 ft, with massive trunks. Its dark green scale-like foliage forms flattened fans, and its reddish-brown bark peels in strips. For small bonsai, growers choose dwarf cultivars with very fine, compact foliage, such as ‘Yatsubusa’, ‘Chirimen’ or ‘Sekka’. The dwarf ornamental cultivar ‘Nana Gracilis’, on the other hand, is tricky: it does not bud from old wood, easily loses interior foliage without replacing it, and is usually grafted, with an unsightly swelling at the base of the trunk.

This is an outdoor bonsai. Keep it in full sun throughout the growing season and give it plenty of light in winter. Shelter it from strong wind, especially in winter, as well as from hard frost and icy wind. Its foliage enjoys humid air and suffers in hot, dry wind, so mist it regularly, but avoid wetting it in bright sun, which can leave burn spots. For winter, some collections move their trees into a cold shelter kept just above 32 °F: the tree must be fully dormant before it goes in and should come out before it starts growing again. Check the root ball’s moisture weekly while it is stored.

Soil mix

Use a free-draining, slightly acidic mix: hinoki dislikes lime. In hot climates, add a little humus to hold more water. For conifers, public bonsai collections use a mix of roughly half coarse sand, one quarter loam and one quarter peat or leaf mold.

Watering

Unlike many conifers, hinoki is thirsty and will not tolerate its soil mix drying out completely. Water as soon as it starts to dry, without leaving the roots constantly soaked. Lay your palm on the mix: if it feels dry, water. Fill the pot with water, let it drain, then fill it again so the whole root ball gets wet. Use lime-free water, such as rainwater. In winter, water less, but never let the root ball dry out.

Fertilizer: during the growing season, apply a solid organic fertilizer every four weeks or a liquid fertilizer every week. Another approach is a very dilute solution every one to two weeks from spring to midsummer, then every two to three weeks until fall, before stopping.

Pruning

Hinoki needs constant foliage care. Throughout the growing season, pinch new shoots regularly to keep the tree compact: if they grow too long, the interior of the canopy loses its foliage, and that loss cannot be undone. Also thin out excess or overlapping fans so light reaches the inner and lower twigs; scales that get no light die and do not grow back. Shaded foliage often dies back in winter.

Keep in mind that new buds appear only on branches that are still green, never on mature wood. Before shortening a branch, make sure it will keep some foliage, and pick a tree whose branches are already well placed. Avoid heavy pruning in summer.

Hinoki suits every style except broom, in all sizes.

Wiring

Styling can be done at any time of year. Conifers are wired with annealed copper, which is harder than aluminum, about one third the thickness of the branch and wound at roughly 45°. Hinoki branches take a long time to hold a new position and often need rewiring several times. Check the wire regularly, since a branch can grow around it within one to four months, and never leave it on for more than a year, or it will girdle the branch. Remove it by cutting at every turn rather than unwinding. On very old trees, taut nylon line works better than wire, and repositioning a branch can take two to three years. Don’t wire a weak or freshly repotted tree.

Repotting

Repot a young tree every two to three years; older or large trees can wait four to five years or longer. The best time is early spring, as growth begins; late summer is another option. The roots grow quickly and tolerate substantial pruning: trim about 1–1 in from the sides and bottom of the root ball and cut any root thicker than a pencil before setting the tree back in fresh mix.

Hinoki is propagated from seed, cuttings and air layers. Seeds need a cold treatment and can take up to a year to germinate; sow them outdoors in spring. Take softwood or semi-ripe cuttings in late summer, and air layer in late spring.

As for pests, watch for scale, spider mites and aphids, and treat them with a suitable product. Tip blight, which kills the ends of the twigs, is treated with a specific fungicide. Before assuming disease, remember that foliage browning inside the tree is often simply short of light.