Pomegranate bonsai

Placement

Pomegranate is a deciduous outdoor tree native to a region stretching from Türkiye to Afghanistan. During the growing season, set it outside in full sun, in a warm, airy spot: it loves heat, and its fruit ripens only if fall stays warm. In hot, dry climates, a bonsai in a small pot appreciates light shade during the hottest afternoon hours.

In the ground, pomegranate tolerates light frost, but a bonsai, whose roots have little protection, should be sheltered as soon as temperatures drop below 32 °F in fall, ideally once the leaves have dropped. The ideal winter home is a frost-free cold frame or cold greenhouse at 36–46 °F; a bright garage also works. A cool winter helps it start growing earlier the following spring. Do not grow it indoors: it weakens there and falls prey to pests.

A vigorous pomegranate is rarely attacked. If it is weakened by a poor location or unsuitable care, aphids, scale, whiteflies, mealybugs and mites can move in: improve its growing conditions and treat with a suitable product. Powdery mildew sometimes appears in very damp weather. The pomegranate plant profile covers the shrub in the ground, its flowers, its fruit and its hardiness.

Soil mix

Choose a free-draining bonsai mix with a slightly acidic to neutral pH, no higher than 7. A blend of akadama, pumice and lava rock works well. Akadama, a fired Japanese clay, should be sifted before use to remove dust; it holds water and breaks down in about two years. Pumice holds water and nutrients and helps the roots branch; lava rock adds structure and aeration. In a wet climate, increase the share of draining materials; if you cannot check the tree often, a little more akadama keeps it moist for longer.

Watering

Water when the soil begins to dry, then soak the whole root ball until water runs from the drainage holes. There is no fixed schedule: needs rise sharply as the flowers open and through summer, and a small pot in full sun can dry out in a single day. So check the soil with a fingertip every day during the growing season. In winter, simply keep it slightly moist. Avoid hard, alkaline water: used repeatedly, it causes chlorosis, a yellowing of the leaves. Overwatering rots the roots.

Fertilizer: during the growing season, apply solid organic fertilizer every four weeks or liquid fertilizer every week. On a mature tree, to encourage flowers and fruit, choose a fertilizer low in nitrogen and high in phosphorus and potassium. Do not feed the tree while it is in bloom. If instead you want maximum growth to develop a young tree, remove the flowers and give a high-nitrogen fertilizer.

Pruning

• Structural pruning: do it during winter dormancy, when the bare branches are easy to see.
• Maintenance pruning: during the growing season, cut new shoots back to one or two pairs of leaves once they reach about 4–6 in.
• Keeping the flowers: flower buds form at the tips of new shoots. For flowers, let the shoots grow freely from midsummer until flowering is over, then resume pruning.
• Fruit: allow only a few fruits to develop; too many exhaust the tree.

Styles: pomegranate is most often trained as an informal upright (moyogi), in every size; ideally choose a tree large enough to keep its fruit in proportion. The dwarf cultivar ‘Nana’, with fine twigs and small fruit, suits small bonsai. The ‘Nejikan’ variety develops a twisted trunk and branches with age that are highly prized. Some shoots carry thorns, and the bark, smooth and gray-brown on young trees, becomes furrowed and flaky with age. Pomegranate can live for several hundred years.

Wiring

You can wire at any time, but it is easiest in winter when the tree has no leaves. Young twigs are flexible and easy to shape; old branches, stiff and brittle, call for great care. For a deciduous tree like pomegranate, use aluminum wire about one third the thickness of the branch, wound at roughly 45°. Branches set in one to four months; watch the wire during the growing season and remove it, cutting at every turn, as soon as it starts to mark the bark. To lower a thick branch that is too stiff, use a guy wire anchored to a strong root or to the pot.

Repotting

Repot every two to three years in early spring, when the buds begin to extend but before the leaves open; an old specimen can wait four years or more. The roots tolerate heavy pruning. Use the free-draining mix described above.

Propagation: sow seed in spring at 55–64 °F. Take hardwood cuttings in spring before the buds open and semi-hardwood cuttings in summer; root cuttings also work. Air layering is done once the spring growth has hardened off.