The Pittosporum genus comprises diverse evergreen shrubs and small trees valued in landscaping for their dense foliage and occasional fragrant flowers. They are frequently chosen for hedges, screens, and foundation plantings due to their adaptability and generally quick establishment. The speed at which a Pittosporum plant grows is highly variable, depending on both the specific species and the environmental conditions.
Defining the Growth Rate
Pittosporum is classified as a medium to fast-growing genus. Under optimal conditions, most popular varieties achieve an annual vertical growth of 1 to 2 feet (30 to 60 centimeters). Certain fast-growing cultivars, especially in warm climates with consistent moisture, can sometimes push this rate to nearly 3 feet in a single growing season.
The growth rate is not constant throughout the plant’s life cycle. Young plants require time to establish a robust root system, meaning initial growth may appear slower in the first year or two. Once the root system is fully developed, above-ground growth accelerates significantly, reaching maximum speed before slowing down as the plant approaches maturity. This rapid growth phase makes Pittosporum a favored choice for quickly creating privacy screens and hedges.
Environmental Factors Influencing Speed
The rate of growth defined by genetics is influenced by external factors, starting with light availability. Pittosporum species perform best and exhibit the fastest growth when provided with full sun (at least six hours of direct sunlight daily). While they tolerate partial shade, insufficient light causes the plant to grow slower and potentially develop a thinner habit as it stretches toward the light source.
Soil quality and drainage are major determinants of growth speed. These plants thrive in fertile, moist, and very well-drained soil. Poor drainage or heavy clay inhibits growth and may lead to root rot. Adequate organic matter in the soil supports faster root expansion, which directly correlates with vigorous top growth.
Water consistency is particularly important during the establishment phase, as regular, deep watering supports rapid growth. Though mature plants are relatively drought-tolerant, prolonged water stress halts growth entirely as the plant conserves energy. The climate, specifically the USDA Hardiness Zone, dictates the length of the growing season; growth is maximized in warmer zones, typically 8 to 11, and slows dramatically during cold winters.
Managing and Controlling Growth
Because the genus is known for quick growth, gardeners often intervene to maintain a desired size and shape. Pruning is the primary method of control, with the best time for major cuts being in late winter or early spring just before new growth begins. Light tip-pruning can be done throughout the year to encourage bushiness and denser foliage.
For significant size reduction or rejuvenation, it is possible to cut back up to one-third of the plant, focusing on removing older, thicker branches. Excessive or heavy pruning should be approached with caution, as cutting into very old wood may not stimulate new growth in all species. Regular maintenance, such as trimming one to three times during the growing season, is necessary to keep hedges neat and at the appropriate size.
Proper spacing at planting is an important management consideration to accommodate fast growth and prevent overcrowding. For container-grown Pittosporum, the rapid growth rate means the plant quickly becomes root-bound. Containerized plants require more frequent root pruning and repotting every few years to ensure continued health and moderate overall size.
Species-Specific Growth Variations
The general growth rate of 1 to 2 feet per year does not apply to all 200 species and numerous cultivars within the Pittosporum genus. Fast growers, like many varieties of Pittosporum tenuifolium, exemplify the high end of the growth scale. P. tenuifolium cultivars such as ‘Silver Sheen’ can add up to 2 feet of height annually, maturing into large shrubs or small trees reaching 12 to 15 feet.
In contrast, several compact cultivars have been bred for a slower growth rate and smaller mature size. Pittosporum tobira ‘Wheeler’s Dwarf’ is a prime example, growing moderately slow to 2 to 3 feet tall with a spread of 4 to 5 feet. Another slow-growing option is Pittosporum tobira ‘MoJo’, a dwarf variety that rarely exceeds 3 feet in height. Selecting these compact varieties is the most effective way to manage growth rate, as they require significantly less pruning and maintenance.