Cold Tolerant Pawpaw Trees

Characteristics

• Asimina triloba is a perennial deciduous tree which can grow anywhere from 10 feet to 25 feet, and generally in the shelter of larger forest trees. The leaves grow up to 12 inches long, turning yellow in fall. Their drooping habit gives the narrow conical tree a tropical appearance.The hanging flowers are dark red and may contain a number of ovaries but do not pollinate easily as the release of male pollen often lags well behind the female receptors. Although the flowers are complete, containing both male and female parts, cross pollination is required. Fruit from a single flower form in a cluster pointing out or up, like bananas. More often the plants regenerate by shooting from horizontal roots, eventually forming a thicket of plants.

Habitat

• The pawpaw is a far more cold tolerant plant than its tropical cousins of the Annonaceae family, the soursop and custard apple. They may be found as far north as southern Ontario on the shores of Lake Ontario; south to eastern Texas and Oklahoma; and west to south eastern Nebraska and Kansas, including southern Michigan. This includes Zone 5B of the USDA plant hardiness map, which is designated an average minimum temperature of -15 Fahrenheit to -10 Fahrenheit.

Growing Pawpaws

• The pawpaw is most successfully grown from seed for the first two years under filtered light conditions such as a canopy of larger trees. The seeds require refrigeration to break dormancy; planting the seeds outdoors and allowing them to overwinter will accomplish the same thing. Grow in deep, fertile, well-drained soil with a pH of 5 to 7. Water well, but do not allow the pawpaw to become waterlogged. Once the tree is two years old it will benefit from full sun, but the large leaves are vulnerable to strong winds. The fruit are ready to harvest when they have darkened and wrinkled, usually in fall.

Pawpaw Development

• In its natural state the pawpaw produces little fruit due to pollination problems. In Florence, Italy research is being conducted to improve the productivity, fruit quality, size and post harvest handling of the pawpaw. The pawpaw is cold-tolerant, which makes it suitable for development in cooler climates as an ornamental and food plant. The pawpaw has been found to contain anti-tumour and pesticide chemicals and has the added advantage of not being subject to disease or pests.