Kiwifruit has become a staple in the produce sections of grocery stores in North America. Its sweet-acidic flavor, soft pulpy texture and bright-green colored flesh have quickly made the fuzzy brown egg-shaped "Chinese gooseberry" a favorite of exotic fruit-lovers. Its high concentration of vitamin C makes it as healthful as it is delightful. In this excerpt adapted from the CD-ROM, Uncommon Fruits Worthy of Attention, longtime Organic Gardening contributor Lee Reich, Ph.D., explains how to grow your own kiwifruit anywhere in North America.
The kiwifruit found in grocery stores (Actinidia deliciosa) is a product of New Zealand that thrives where winter temperatures dip to just 30 and 45 degrees Fahrenheit, which includes USDA Hardiness Zones 7 through 9. Gardeners in northern zones can grow this exotic treat, too—hardy (A. arguta) and super-hardy kiwifruit (A. kolomikta) survive temperatures as low as -25˚F and -40˚F, respectively.
Grocery store kiwifruit
Kiwifruit (A. deliciosa)—which has the largest edible fruits of the species and is therefore the actinidia of commerce—can be grown in temperate climates experiencing some, but not excessive, winter cold (USDA Hardiness Zones 7 through 9). At least 30 days of cool weather— between about 30 and 45˚F—are needed before vines can resume normal growth in late winter or early spring, though some cultivars will resume growth with a shorter cold period. The latter are referred to as "low-chill" cultivars. In the dead of winter, the vines are apt to be damaged if the mercury dips below somewhere between 0 and 15˚F (researchers in various parts of the globe have not reached a consensus on this figure). Kiwifruits need a long growing season—200 to 225 days—to ripen their fruits.
Ripe fruits are hairy, brown, and about the size of a hen's egg, with a vitamin C concentration twice that of oranges. The emerald green interior is speckled near the core with tiny black seeds, and fruit sliced crosswise exhibit the lighter colored rays that are the source of the genus's name ("actin" means "ray" in Latin).
As an ornamental vine, A. arguta has been sold as "bower vine," and the fruits have been known as "bowerberry." By any name, this vine is a rampant grower, with wild vines sometimes climbing 100 feet high into trees in forests of Japan, Korea, north China, and Siberia. Cultivation can suppress and redirect some of this energy. Vigor aside, this plant has a more delicate appearance than the semi-tropical kiwifruit plant of A. deliciosa. The leaves of hardy kiwi are only the size of apple leaves, and are attached to the stems on red petioles. The contrast between red and green is pleasant, not harsh, because of the pale intensity of both colors.
As implied by the name and the native habitat, this plant can tolerate cold. Plants generally are hardy to about -25˚F (adapted to USDA Hardiness Zones 4 through 7), and require about 150 frost-free days to ripen their fruits.
The fruit itself looks quite different from that of the grocery store kiwifruit. Hardy kiwifruits are smaller, an inch or so long. Fruits are borne in clusters and have smooth, edible skins so can be eaten just like grapes. The hardy kiwifruit has the same emerald-green interior and similar flavor to the grocery store kiwifruit, except that hardy kiwifruits are sweeter.
The Russians have been breeding hardy kiwifruits for the past few decades, and some of those cultivars now are available outside Russia. Other available cultivars are the result of limited, recent breeding efforts in North America, or else are propagated from mature vines growing at old estates and public grounds. The latter category includes plants such as 'Geneva' (from a plant at the New York State Agricultural Experiment Station at Geneva, New York), 'MSU' (a plant at Michigan State University campus), and 'Dumbarton Oaks' (a plant at an old public garden in Washington, D.C.).
A. kolomikta is another species producing smooth-skinned, small fruits on a cold hardy—in this case extremely cold hardy—vine. The plant reputedly can tolerate winter lows below -40˚F (it's hardy in Zones 3 through 7) and needs only about 130 frost-free days to ripen its fruit.
For want of a better name, this plant has been referred to as "hardy kiwifruit," "super-hardy kiwifruit," and "Arctic beauty kiwifruit."
There are a few differences between this species and A. arguta. A. kolomikta fruits are smaller and often have the nasty habit of dropping their ripe fruits to the ground. The fruit is brimming with vitamin C (average of 1,000 mg per 100 g of fruit has been reported; as compared with 60 for oranges). The plant itself is less rampant than that of the previous two species, and prefers some shade, especially when young.
Male vines have a decorative white and pink variegation to their leaves, though the variegation is not present on young plants or those grown in too much shade.