Have you tasted these remarkable miniature kiwis yet? Every bit as delicious as the larger, more familiar fuzzy kiwi, hardy kiwis are much easier to grow and eat (skin and all). And just about every home gardener in North America can grow them.
Hardy kiwi is a catchall term for types of kiwis (Actinidia) that, when dormant, can survive temperatures as low as -40oF (USDA Hardiness Zone 3). These beautiful, vigorous natives of Russia, China, Japan, and Korea have deep green leaves and long whiplike vines that can grow as much as 20 feet in a season. In the wild, they may climb 50 feet or more into treetops.
The fruits, somewhat larger and rounder than grapes and with a more opaque green skin, hang in long, heavy clusters. Like fuzzy kiwis, they have soft flesh with small, black, crunchy seeds. They taste sweeter than fuzzy kiwis and don't require peeling. Hardy kiwis are not common in markets because they don't ship very well. But you might notice them sold in specialty markets as "baby kiwis."
The short answer is, just about everywhere. Since hardy kiwis are cold tolerant but don't require much winter chill to set fruit, most have a wide growing range -- from Florida to Massachusetts and San Diego to Vancouver -- anywhere temperatures stay above -25oF (zone 4). In colder parts of this range, plants need protection during occasional false springs, when a brief warm period induces leaves and shoots to sprout, only to be set back in the cold snap that follows. When that happens, the year's crop will be pretty much wiped out.
If you live where winter temperatures dip below -25oF (zone 3 and colder parts of zone 4), you have two options. You can either grow the hardiest of the hardy kiwis, (A. kolomikta) 'Arctic Beauty', or grow any of the hardy species in 15-gallon pots in a greenhouse. Greenhouse-grown plants should fruit as long as they receive at least 100 hours below 45° F during the dormant season. Hardy kiwis require considerable amounts of water during the growing season, so they may not be well suited to drought-prone areas.
If you prefer to plant bare-root, buy and plant hardy kiwis in winter or early spring, when you would any other bare-root fruit. In cold-winter areas, plant after all chances of frost have passed, from spring until midsummer. In areas with long growing seasons, plant hardy kiwis anytime, but do avoid the hottest parts of summer, when transplant stress is high.
Hardy kiwis must have strong vertical support. In their native forests, these heavy vines climb trees. In a home garden, they require a sturdy structure such as a patio overhead or a trellis with 4-by-4 supports.
Kiwis are dioecious, meaning you need to grow male and female plants in order for the female plants to set fruit. A single male will pollinate at least eight females. Space plants about 12 feet apart. If space is limited, place both a male and a female plant in one planting hole, or grow (A. arguta) 'Issai', the only self-fertile variety.
Hardy kiwis need rich soil. Generally, about 10 pounds of compost or manure per plant, in both early and late spring, is enough. However, if growth seems to lag, or if leaves are pale, supplement with a pound of soy or cottonseed meal per plant in late spring or early summer.
Growers have different fertilization schemes. Roger Meyer, a commercial grower in southern California, applies half of his plants' yearly fertilizer allotment in late winter and the rest in monthly applications through July. Michael McConkey, who grows and sells hardy kiwi at his nursery in Virginia, fertilizes twice a year. He applies a third of each plant's yearly allotment before spring growth starts and the rest after fruit sets.
Pruning. Hardy kiwis are long-lived. Careful and rigorous pruning is essential to create strong and productive plants. In their native forests, these plants put most of their energy into climbing to reach the sunlight at the top of the trees. In your garden, however, you want them to direct that energy into making fruit. You need to prune often, once every few weeks during the growing season. As one grower notes, "You can't overprune a kiwi."
Your goal is to create an umbrella-shaped plant. In the first year, limit each plant to one vertical shoot, and direct that shoot to the top of its support. That shoot will become the plant's trunk. Wire or tie it loosely to the support.
In the first dormant season, prune each vine back to the top of its support.
In the second growing season, select two strong side branches near the top of the trellis and train them horizontally along the support. In the second dormant season, prune the side branches back to 1 to 2 feet long (12 to 18 buds on each). New branches will sprout from these side branches and become next year's fruiting wood.
From the third year on, prune female kiwis in the dormant season so that fruiting branches are at least 6 inches apart along the main branches. Cut out any dead or weak wood, and all tangled branches. Cut off branches that reach the ground or are so close that their fruit clusters could reach the ground.
In cooler areas, prune males back hard in summer. Prune as often as necessary thereafter to keep them tidy and to prevent them from overtaking the female vines. Restrict pruning to spring and fall in hot climates because bare branches are susceptible to sunburn. Whenever you prune, be sure to leave some of the previous year's wood so the plants flower and produce pollen.
Vines have a tendency to bleed if pruned too late in the dormant season, so do dormant pruning in the dead of winter.
Most hardy kiwis take about three years to bear fruit, though 'Arctic Beauty' and 'Issai' often bear the first year after planting. Depending upon your region, most 'Arctic Beauty' fruits ripen in early to mid-August, while fruits of the others ripen from late August through mid-October. Fruits are picked hard-ripe, then allowed to soften off the vine, like avocado and fuzzy kiwi.
Starting in late August, pick a few fruits and let them ripen on a windowsill or in a paper bag. Taste them when the flesh is soft and the seeds are black. If they don't ripen, wait several weeks and then test a few more fruits. When you notice the first fruit softening on the vine, pick all the fruit. Store hard-ripe fruit in airtight plastic containers or sealed bags in the refrigerator. Take out a few at a time to ripen. Eventually, all of the fruit on the vine will soften, but if you wait that long, you will have an overwhelming harvest of fruits that will last only a short time. Regardless of when you start to harvest, be sure to pick all the fruits before the first frost.
In Russia, hardy kiwis are made into jam, but they're also delicious simply sliced in half and drizzled with fresh cream.
Actinidia arguta -- Zones 5 through 10. Mature plants produce up to 100 pounds of fruit per season. Pest- and disease-free.
'Anna' -- Zones 5 through 10. In Russia, this variety is called 'Ananasnaya', meaning "pineapple-like." It is vigorous, productive, and promising commercially. Very ornamental with red leaf stems. One of the best-tasting ("addictive") and sweetest of the hardy kiwis.
'Dumbarton Oaks' -- Zones 5 through 8. Excellent flavor and early ripening.
'Issai' -- Zones 6 through 10. Only self-fertile variety (a male pollenizing plant is not needed). Fruits the first year after planting. Medium-sized green fruit. Susceptible to spider mites in hot, dry climates.
A. cordifolia -- Zones 5 through 10. Perhaps the sweetest of all and the first to ripen. It has been less successful in the Pacific Northwest.
A. kolomikta 'Arctic Beauty' -- Zones 3 through 8. Best suited to short-season and cold-winter areas. Compared to A. arguta, plants are smaller and more delicate; fruits are smaller and ripen earlier. Fruits first year after planting. Plant where it receives partial to full shade. Leaves of male plants start the season deep green, then paint themselves with splashes of white and pink.
A. purpurea 'Hardy Red' -- Zones 5 through 10. Vigorous vine; oblong red fruit is sweet with a bit of tartness.
Nan Sterman is a gardener and writer who lives in Olivenhain, California.
Article published on June 23, 2008.