Common myrtle bonsai

Placement

Myrtus communis is a Mediterranean evergreen shrub that cannot take frost. The simplest approach is to grow it outdoors in the warm season and shelter it in winter. It can also stay indoors all year, as long as it gets plenty of light and fresh air.

From spring to fall, set it in the sun, in a spot sheltered from cold, drying winds; during very hot summers, partial shade suits it better. It needs a long, warm summer to flower well: its fragrant white flowers open in late summer and are followed by pea-sized, bluish-black berries.

In fall, before frost, bring it into a cool room, ideally around 50 °F, at a south-facing window or under a grow light. Avoid a warm room with dry air and poor light: those are exactly the conditions that attract scale and whiteflies.

Soil mix

Myrtle does not tolerate lime well, either in the soil or in the water. Use a lime-free bonsai mix with added peat or kanuma. The mix must hold enough moisture, since the root ball should never dry out, while draining well to prevent root rot. There is no need for an oversized pot: slightly crowded roots encourage flowering.

Watering

This is the key point. The root ball must stay moist at all times without ever becoming waterlogged, because drying out completely can kill the tree very quickly. Water thoroughly as soon as the surface of the mix starts to dry, until water runs from the drainage holes. Do not follow a calendar: a pot in full summer sun dries far faster than one in a cool room in winter, where it stays damp much longer. Check the mix regularly and adjust.

Use rainwater whenever possible, or else water low in lime.

Fertilizer: during the growing season, apply liquid fertilizer every week. In winter, do not feed a myrtle kept cool. If it overwinters above 50 °F and keeps growing a little, give it liquid fertilizer twice a month.

Pruning

Its leaves are small, lance-shaped, and dark green, and it branches very well, which makes it an excellent subject for fine ramification. After flowering, let new shoots extend to six to eight pairs of leaves, then cut them back to one pair on each twig: new buds then form and fill out the canopy.

The trunk thickens slowly and the cinnamon-colored bark becomes lightly furrowed with age, so patience is needed for an impressive trunk. Seal large wounds with cut paste. Myrtle suits many bonsai styles, and especially the broom style, which shows off its dense branching.

Wiring

Wiring works on young shoots and twigs that are still flexible. Older branches become stiff and break easily, so the structure is set early and then refined by pruning. Softer anodized aluminum wire is easy to handle on these fine twigs. Choose wire about one third the thickness of the branch and wrap it at roughly 45°, which lets the branch thicken while keeping its shape. If a thicker branch has to be guided, protect it first with soaked raffia. Wire every branch you plan to move before bending any of them.

Twigs take a few months to hold their position, often six to twelve months, but the wire can mark the bark within one to four months during active growth, so check it often. To remove it, cut it at every turn rather than unwinding it, which could damage the tree. Bend by pushing from the inside of the curve, and avoid bending the same branch repeatedly.

Repotting

Repot young trees every two to three years and older ones every three to five years. The best time is early spring, when the buds begin to swell. Gently remove part of the old mix, trim overly long roots without taking more than 30% of the root mass, replant in fresh lime-free mix, and water thoroughly. Afterward, keep the tree in a stable spot and do not fertilize too soon.

Propagation: from seed or cuttings. Semi-hardwood cuttings taken in spring or summer give the best results, and air layering also works.

Pests and diseases: scale, mealybugs, and whiteflies are the usual enemies, especially indoors in winter with warm, dry air and little light. Outdoors in hot, dry weather, scale, spider mites, and thrips can also appear. Treat with a suitable product, but above all improve the growing conditions. In spring, a single late frost can damage young shoots, so wait until the risk has passed before moving the tree outside.