If you're looking for an attractive flowering shrub that also brings sweet fragrance to the garden, the pittosporum plant (Pittosporum tobira) makes a great choice. Also called the Japanese mock orange because it's an Asian native, this densely branched, rounded shrub needs only basic care to grow well.
The pittosporum plant grows as a reliably hardy plant in U.S. Department of Agriculture plant hardiness zones 8 through 10. The commonly grown variety reaches a height of 8 to 12 feet at maturity, with a spread that can cover 12 to 18 feet. Its growth rate is slow-to-moderate, and it generally adds 1 or 2 feet to its height each year when grown in ideal conditions. Once it reaches its mature size, growth slows and the plant adds little or no additional height. Dwarf cultivars such as "Wheeler's Dwarf" (Pittosporum tobira "Wheeler's Dwarf) and "Mojo" (Pittosporum tobira "Mojo), which are only 2 or 3 feet tall at maturity, tend to grow at a slightly slower rate than the larger, more widely grown plant.
2. Promoting Growth
The pittosporum plant tolerates full sun or partial shade, but it develops an especially attractive, bushy shape with branches radiating out from the main stems when growing in bright sun for most of the day. In shade, the plant may grow slightly taller, but its branches could end up more widely spaced and it can become a bit leggy over time. Pittosporum is exceptionally tolerant of heat, and also grows well in regions with salty air or soil, making it a good choice for coastal locations.
3. Controlling Size
You can help control the size of a pittosporum plant by pruning it regularly, cutting branches back by about one-third or less. This is best done immediately after the plant flowers in the spring, because it blooms on old wood and needs to put out growth during summer and fall that develops flower buds for the next season. An older plant also responds well to severe pruning of most or all of its branches, quickly putting out bushy new growth at branch tips. You can also train a young plant into a more treelike form by choosing two or three main stems and cutting away any others, then removing new growth from the lower portions of these main trunks in subsequent years.
4. Other Needs
A young pittosporum grows at its fastest rate when given moderate moisture, although it's an especially drought-tolerant plant once it's well established. It also does best when grown in fertile, well-drained soil and can do poorly in soil that tends to stay soggy for long periods. If your soil drains slowly, add some fine sand at planting to improve its drainage. You can also mix in some compost to increase the organic content and promote soil fertility. Pittosporum is usually free of any serious pest or disease problems, but it can attract mealybugs and aphids. These are best controlled by spraying with insecticidal soap, diluted at a rate of 5 tablespoons per gallon.