Thorny elaeagnus bonsai

Placement

Thorny elaeagnus is grown outdoors year-round. It needs bright light, with at least four to six hours of sun a day, in full sun or partial shade. In a very hot climate, protect it from intense midday sun, which can scorch the leaves. Good air movement around the foliage limits fungal diseases; the tree also copes very well with wind and even salt spray.

It suits temperate climates and tolerates frost. In the ground, the species survives severe winters, down to about 5–14 °F, but the roots of a bonsai in a shallow pot are far more exposed. Where temperatures often fall below 14 °F, move it to a cold frame or an unheated greenhouse during hard freezes, and vent them on sunny days. In a milder climate, set the pot on the ground, out of the wind, and wrap it in insulation if you like. As with all outdoor trees, avoid heated rooms: it needs the rhythm of the seasons.

Soil mix

Perfect drainage is what matters most: water must flow through the pot and out the bottom freely. Use a free-draining bonsai mix, for example equal parts akadama, pumice and lava rock, sifted to remove dust. If you cannot water often, raise the share of akadama, which holds more water; in a very rainy climate, add more lava rock. The species copes with poor soil and with acidic, neutral or alkaline pH, but a very chalky mix can turn its leaves yellow.

Watering

Keep the soil evenly moist, never soggy. Always check before watering: push a finger about 0 in into the soil and water when the surface is dry, soaking the whole root ball until water runs from the drainage holes. Then let it dry slightly before the next watering. Needs rise during the growing season, especially for a tree in full sun; they drop markedly in winter, but the root ball should never dry out completely. Too much water and too little air around the roots encourage root rot.

Feeding: every four to six weeks, from early spring through fall, use a balanced solid organic fertilizer placed on moist soil so it does not burn the roots. Stop in winter. Stick to the recommended dose: overfeeding produces too many leaves and weak branches.

Pruning

Thorny elaeagnus takes pruning very well, even hard pruning, and is easy to shape. Do structural pruning in early spring, before new growth, and remove any dead or damaged branches at the same time. Use a concave cutter on thick branches and cover large wounds with cut paste.

During the growing season, the species throws long, vigorous shoots in every direction: shorten them regularly to keep a compact outline. Pinch young shoots to trigger side branching, and prune the top and outer canopy harder, since they are more vigorous, so the interior stays full. Remove suckers from the base. On a variegated tree such as ‘Variegata’, cut out shoots that have reverted to plain green. Keep in mind that flowers form on old wood: if you want the fragrant fall bloom, do not shear off all the branches. Wear gloves, because the stems carry thorns.

Wiring

Its twigs are thin and delicate: wire carefully to avoid damaging them. Choose aluminum wire about a third as thick as the branch, applied at about 45° from the base toward the tip; wire every branch you plan to move before bending any of them, and apply pressure on the inside of the curve. Evergreens can be wired year-round, but check often during the growing season, because wire can mark the bark within one to four months. Remove it by cutting at each turn. For a branch that is too thick, use a guy wire instead.

Repotting

Repot every two or three years, or when roots fill the pot, in early spring, just before growth resumes. Shorten overly long or damaged roots, removing no more than about a third of the root mass, and replace the old soil with a fresh, free-draining mix. Water thoroughly, then keep the tree in shade and out of strong wind for a few weeks until it recovers. Do not feed too soon or add hard pruning during that time.

To propagate it, take semi-hardwood cuttings 4–6 in long with a few leaves in late summer or early fall. Strip the lower leaves, dip the base in rooting hormone and insert them in a free-draining mix of sand and peat, kept humid and in indirect light; rooting takes from a few weeks to a few months. Layering also works: wound a branch and bury it so it roots. The species can be trained into a variety of styles.

The tree resists pests well, but watch for aphids, spider mites and scale: sticky residue or fine webbing should put you on alert. Treat with insecticidal soap or neem oil. Against powdery mildew and root rot, both encouraged by overwatering and poor air movement, remove affected parts promptly and correct your watering.