Pittosporum Nigricans as a Hedge

Pittosporum Varieties

• Pittosporum nigricans shrubs generally grow to a height and width of 8 to 15 feet, but there are shorter and even dwarf cultivars and hybrids that grow to no more than 2 or 3 feet tall. Some cultivars have small leaves while others have larger leaves. “Marjorie Channon” or variegated kohuhu (Pittosporum tenuifolium “Marjorie Channon”) grows to a height of 8 to 12 feet and width of 6 to 8 feet with light green leaves that are edged in creamy white. It produces dark red flowers in the spring. The leaves are small to medium in size with slightly undulating edges. “Silver Sheen” kohuhu (Pittosporum tenuifolium “Silver Sheen”) grows to a height of 15 to 20 feet and a width of 6 to 8 feet with black stems and small green leaves that have a silver sheen. It produces purple spring flowers.

Growing Requirements

• Pittosporum nigricans shrubs are hardy in U.S. Department of Agriculture plant hardiness zones 8b to 11. Their high tolerance for salty conditions makes them ideal for hedges near the ocean, and they are rarely bothered by deer. They grow equally well in partial shade or full sun. Average soil is fine for these shrubs as long as it drains well. Slow-draining soil can cause crown or root rot. They prefer slightly acidic soil with moderate fertility and may become deficient in magnesium when planted in alkaline soil. These are drought-tolerant shrubs, but they should be watered two or three times per week for the first year and every two weeks or so after that during extended dry periods. Give each shrub 2 to 3 gallons of water each time. Sprinkle 2 or 3 tablespoons of 10-10-10 fertilizer per shrub around the hedge in late winter or early spring before the shrubs start their new spring growth.

Planting and Pruning

• Pittosporum nigricans shrubs should be planted 4 to 6 feet apart for a hedge. They will quickly fill in the space to form a solid barrier of stems and foliage, but there will be ample room for good air circulation which will reduce the risk of leaf spot diseases. Reduce the height of each shrub by one-third right after planting and again the following summer. Always prune these shrubs in the summer right after they bloom. In subsequent years, trim them back by 6 inches after they put on 1 foot of additional height. Clippers can be used to shear these shrubs, although they will leave ragged edges on larger leaves. Pruners may be more time-consuming but will result in a neater-looking hedge. Shape the hedge so that it is more narrow at the top so sunlight can reach the lower branches. Disinfect the clippers or pruners with rubbing alcohol after using them.

Pests and Diseases

• Pittosporum nigricans shrubs can be afflicted by fungi which cause them to develop branch dieback and galls. If this happens, trim off the affected branches to healthy wood about 6 inches below the diseased section. Use disinfectant to sterilize the pruners between cuts to prevent spreading the disease. Aphids, mealybugs and whiteflies sometimes attack pittosporums. They can usually be controlled by simply spraying them off the shrubs with a strong stream of water. Severe infestations of these bugs and scale insects can be eliminated with insecticidal soap. Spray the soap directly on the bugs which often congregate on the bottoms of leaves. Insecticidal soaps are usually sold pre-mixed in ready-to-use spray bottles. These shrubs are also susceptible to root-knot nematodes which will cause them to wilt, develop yellow leaves and appear stunted; there is no cure for them.