Actinidia kolomikta
A. kolomikta, sometimes called "Arctic Beauty Kiwi," can be hardy below -40° F, although some plants may not bear fruit the season following a winter that cold. This plant is native to northern China, Siberia, Japan and Korea. It's a twining vine that will grow about ten feet tall and spread about three feet wide. A. kolomikta foliage is attractive, with variegated pink, white and green leaves, and is sometimes planted for its ornamental value alone. The male plants are commonly more variegated than female plants, and variegation increases as the plants mature.

Plants should begin to bear fruit one to two years after planting, and once established they can live fifty years or more. Only the female plants produce fruit, and they must be grown with a male plant to provide pollen. The small whitish flowers appear in May or June, and pollination is carried out by insects.

The berries begin to ripen in August and bearing may extend into late September. Cool night temperatures facilitate berry ripening. Immature fruit is bright green and shiny. Berries become slightly darker green and somewhat translucent as they ripen and soften. Like kiwifruit available in the grocery store, they are best eaten fresh, and can be refrigerated for a week or two without their quality declining.

A. kolomikta performs best in partially shaded sites with well-drained soil and some protection from strong winds. They are neither drought tolerant nor flood tolerant: if the soil becomes too dry, the vine may survive, but the fruit will drop, and if the soil is too wet, the vine is likely to succumb to root rot. Actinidia vines grow well in soil that is acidic to slightly alkaline (pH 5.5-7.5). Sunlight for most of the day is necessary for best growth and fruiting, but too much sun in winter can harm the vines. To protect them over winter, paint the stems with white latex exterior paint after the leaves have fallen (usually in mid-October). Alternatively, use tree wrap or place a burlap screen south of the trunk before the ground freezes in fall.

Kiwi vines require support.

Actinidia vines require support. Construct or purchase a durable trellis made of metal or wood, with wires or other supports extending horizontally. Wire fencing, supported by side posts, makes an adequate trellis. Actinidia vines climb by twining, rather than by anchoring themselves with tendrils, so the thickness of the supports is not critical. Plant bare-root or container-grown plants early in the spring. Mulch the base of each vine with wood chips, straw, compost or similar material, and train the young shoot to grow up towards the trellis wires. Start the vine climbing up a bamboo pole rather than wire or twine, as this will provide a more stable support. It's best for young stems not to wind too tightly around narrow supports, because the stems will not grow and expand properly if they are tightly coiled.

The year after planting, thicker and more vigorous shoots will emerge from the base of the vine. The straightest and most vigorous of these should be selected as the permanent trunk. The rest of the shoots should be pinched back at the tip and pruned out entirely the following winter. During the first year or two after planting, the vine may not grow very tall. Underground, though, it will be developing a strong root system to support more vigorous growth and fruiting in future seasons.

Once the vine has begun fruiting, it may be necessary to fertilize it yearly at a rate of 1 ounce to 4 ounces actual nitrogen per plant. (For a fertilizer with the analysis of 33-0-0, 3 ounces to 12 ounces would provide this much nitrogen.) Most Minnesota soils have adequate potassium and phosphorous for plant growth and fruiting; however, if a soil test shows a lack of either of these nutrients, be sure to use a complete fertilizer. Apply fertilizer to the entire root zone of the vine, about a ten square foot area around the trunk, in April, May, or June.

A. kolomikta is not a vigorous vine, so little pruning should be necessary. Train the vine to a single trunk, as described above, for best flowering and fruiting, but don't head back or thin out shoots from this trunk, since fruit will be borne along the length of the stems. Cut stems will "bleed" or run with sap, if pruning is done in spring, so any pruning should be done in January and February, with only light pruning in July, if necessary.

Aside from the root rots common to Actinidias in poorly drained soil, there are no significant diseases or insect pests to worry about when growing hardy kiwis.

Some of the best varieties of A. kolomikta have Russian names, such as 'Aromatnaya,' named for its aromatic fruit; 'Krupnopladnaya' which has larger fruits than other varieties; and 'Sentayabraskaya,' which is particularly sweet.

Actinidia arguta
Another hardy kiwi, Actinidia arguta, was known as "Bower Actinidia" for many years, until kiwifruit became popular. Now, it's likely to be listed in nursery catalogs as "Hardy Kiwi." In milder climates, this vigorous species produces hairless, cherry-sized fruit; however, the vine dies to the ground except in the warmest of Minnesota winters. It's only cold hardy to between -10° F and -23° F, depending on the variety. Although the vine will grow back up again from its roots, the flower buds needed to produce fruit will have been killed.

Actinidia arguta is more useful in Minnesota for screening, with red petioles (leaf stalks) that provide an interesting contrast to its green leaves. It can grow more than 20 feet tall in a single season, and spread to eight feet wide. Trellises for A. arguta must be sturdy and firmly anchored, since the vines grow vigorously and can be quite heavy. Because it dies to the ground each year, pruning is limited to removing dead stems from the trellis before growth starts in spring.

Some kiwifruit enthusiasts in the state have harvested crops of fruit from A. arguta by training it on a trellis that can be lowered to the ground for the winter. The vines are then mulched with a thick layer of straw, and become buried by snow as well. In spring, the trellis is brought back to the upright position, the vine and its flower buds having survived winter under the insulating layers of mulch and snow.

If A. arguta is grown this way, prune the vines back severely for best fruiting. In winter, thin out any weak branches and the thick vertical stems known as "watersprouts." Now identify the wood that will be fruitful and the wood that will produce leaves. Fruiting spurs have closely spaced buds. Canes that will produce only leaves in the spring, rather than flowers (and then fruit), have buds spaced farther apart. Prune out most of these vegetative canes. Cut the remaining canes back as far as the short fruiting spurs. Fertility requirements of A. arguta grown for fruit are similar to those of A. kolomikta.

A number of different cultivars of this species are available. The one most commonly found at Minnesota garden centers is 'Issai,' valued as a self-fertile female that produces small seedless fruits. However, this cultivar lacks sufficient cold hardiness to be grown for fruit in Minnesota. If you try growing A. arguta for fruit, plant a male of the same species, since flowering times and chromosome numbers differ between Actinida species; don't rely on a male A. kolomikta as a pollenizer.