Japanese pittosporum

Identification and origin

Pittosporum tobira belongs to the family Pittosporaceae. It is native to East Asia: southern Japan and the Ryukyu Islands, Korea, and Taiwan. Widely planted in the southern United States and southern Europe, it has naturalized around the Mediterranean and on several Atlantic islands.

It is an evergreen shrub or small tree with a dense, rounded to spreading habit, reaching 8–13 ft tall in cultivation and often growing wider with age; growth is fast when young, then slows considerably. The alternate, obovate leaves are thick and leathery, 1–4 in long, glossy dark green with a pale midrib and edges slightly rolled under, and they are crowded in whorls at the branch tips. They curl inward even more when the plant is stressed.

In spring, terminal clusters of five-petaled flowers about 1 in across open creamy white and turn yellow as they age. Their strong fragrance recalls orange blossoms. The fruits are pear-shaped capsules about 1 in across, green turning brown, which split open in fall to reveal red seeds coated in sticky pulp.

There are many cultivars: ‘Variegata’, with gray-green leaves edged in cream, stays around 5–10 ft; ‘Wheeler’s Dwarf’ forms a dense mound about 3 ft tall; ‘Shima’ (Cream de Mint) barely exceeds 2–2.5 ft; ‘Nanum’ is another compact form.

Light

It grows in sun or shade, even fairly heavy shade. Variegated forms appreciate some afternoon shade. If you grow it in a container indoors or under glass, give it the brightest room, in full light.

Watering

In the ground, water regularly during the first two years in dry spells in spring and summer while the roots establish. After that the shrub is quite drought-tolerant, although it looks better with regular summer watering if the soil dries out quickly.

In a container, check the root ball often and water as soon as the surface of the mix dries, keeping it moist but never soggy. A long dry spell causes leaf drop, and overwatering is even worse: in poorly drained soil, root rot kills the plant quickly.

Potting mix

It tolerates sandy, loamy, clay, or chalky soils, acidic or alkaline, as long as they drain well. Growth is fastest in acidic soil of average fertility; in very alkaline soil, micronutrient and magnesium deficiencies can appear.

In a container, use a peat-free, loam-based potting mix, or an equal mix of loam-based and multipurpose potting mix. A 2–3 in layer of compost mulch around planted shrubs keeps the soil moist. A general fertilizer in spring is enough, and only if the soil is poor or the plant is growing weakly.

Temperature

Indoors or in a cool greenhouse it prefers cool conditions: about 50–64 °F by day and 45–55 °F at night. Outdoors it tolerates brief frosts down to about 23 °F and is grown in the ground in USDA zones 8a to 10b; some cultivars, such as MoJo, are hardier. Cold can split the bark, and those wounds let fungi in.

Where it is not hardy, grow it in a large container on the patio and bring it under cover for winter. If you have no room, set the container against a south-facing wall and cover the plant with frost cloth, which gives about 36 °F of protection. In mid-spring, trim off any shoot tips damaged by cold.

Repotting

Plant preferably in fall or spring. For a container plant, choose a pot only slightly larger than the root ball, 1–2 in wider. After two or three years, when the roots fill the container, repot in spring into a slightly larger one.

Pruning

Flowers form on the previous year’s growth: if you want to enjoy their fragrance, prune right after flowering, because later pruning removes the next year’s blooms. It takes pruning well: it can be kept at any height, sheared as a hedge two or three times during the growing season, or trained as a small multi-stemmed tree by removing the lower branches.

An overgrown hedge can be cut back in spring as long as you don’t cut into old, bare wood, but regrowth is slow and sometimes patchy: spread the work over two or three years, removing no more than a third each year, then fertilize. Cut diseased branches 6 in below the symptoms, disinfecting your pruners with alcohol between cuts.

Propagation

Cuttings are easy. From late summer to early fall, take semi-hardwood cuttings 2–3 in long from the current season’s growth, dip the base in rooting hormone, and stick them in a very well-drained mix that is half perlite, keeping humidity high around them.

Layering is even simpler: in spring, bend a low young shoot to the ground and bury part of it until it roots. It can also be grown from seed.

Common problems

• Leaves blackened by sooty mold: scale insects, especially cottony cushion scale, mealybugs, or aphids.
• Shoot dieback and swollen twigs: pittosporum psyllid.
• Under glass or in a sunroom: spider mites and scale; whiteflies can also appear.
• Spots on the leaves: leaf spot diseases, common on variegated forms; improve air flow, avoid wetting the foliage, and clean up fallen leaves.
• White powdery coating: powdery mildew, rarely a concern.
• Yellowing between the veins and along the edges of older leaves: magnesium deficiency, in overly alkaline soil.
• Sudden wilting: root rot in waterlogged soil.
• Leaf drop: loss of older inner leaves is normal; heavy drop within a few weeks can come from frost, overwatering, or a long dry spell.
• Galls on branches: fungi entering through wounds.

The same symptom can have several causes: always check watering, drainage, exposure, and insects before drawing conclusions.

Toxicity

No toxicity has been reported: the plant is classified as non-toxic to dogs, cats, and horses. As with any ornamental plant, discourage children and pets from chewing the leaves and fruits.