Freeze Danger for Pittosporum

Appearance Counts

• Although the pittosporums’ maximum height can vary from 15 to 40 feet if the plants are raised as trees, they are often sheared shorter. They generally produce small, fragrant and bell-shaped flowers in white, yellow or maroon hues in the spring, which are followed by hard-shelled, pea-sized green, white, yellow, orange or brown fruits in fall. Stalks of pittosporum leaves and fruit make attractive additions to floral bouquets, but children should be warned not to eat the berries, which can be toxic.

Where To Grow Pittosporum

• The hardiest varieties of pittosporum, such as karo (PIttosporum crassifolium), lemonwood (PIttosporum eugenioides), desert willow (Pittosporum phillyraeoides), kohuhu (Pittosporum tenuifolium), Japanese mock orange (Pittosporum tobira) and their cultivars can survive in USDA zones 8 through 11. The more tender types such as Queensland pittosporum (Pittosporum rhombifolium), golden fragrance (Pittosporum napaulense), Victorian box (PIttosporum undulatum) and their cultivars should be limited to USDA zones 9 through 11.

Plan for Cold Weather

• To prevent freeze damage, plant only pittosporums that are listed as hardy for your zone. If you must grow a type that is marginal, site it in a protected location, such as on the south side of a building or wall. Low-lying positions or those open on their north or northwest sides should be avoided. Refrain from fertilizing or pruning the shrub in the fall, as this can stimulate new growth, which is much more easily damaged than the old growth. Spray the plant in early winter with an anti-transpirant, which prevents it from losing too much water through its leaves during stressfully cold conditions. Periods when the temperature falls gradually won’t stress a shrub as much as sudden freezes do.

Last-Minute Freeze Prevention

• If your weather is forecast to drop abruptly to temperatures near or below the minimum for your zone, find ways to raise the temperature around your pittosporum. You can set black plastic buckets or garbage cans filled with water around the plant during the day to soak up heat from the sun, which should radiate during the colder night. Another possibility is to place stakes slightly taller than the pittosporum around it, cover those stakes with a blanket, and insert a fixture with a lit incandescent bulb under that blanket. For this to work properly, you need to keep the bulb within 2 or 3 feet of the plant but not touching either it or the blanket. The blanket should rest above rather than on top of the pittosporum and fall all the way to the ground on the sides without touching the leaves. Fluorescent or LED bulbs won’t work for this, as they don’t create enough heat.