Commercial kiwiberry production in Minnesota

Several named varieties of each species are available, and new varieties will likely be available soon thanks to fruit breeding programs across the U.S. 

In the wild, trees shade the trunks of kiwifruit vines. The tops of the plant receive sunlight by growing up into the forest canopy. Successful vine growth and fruit production in a cultivated setting can be achieved by imitating environmental conditions found in its native habitat.

Site

• Plant vines in a location where they will be shaded from afternoon sun and winter sun, ideally north or east of a tree line, building or structure.
  • This location will contribute to the cool, moist soil conditions favored by kiwiberry vines and will help delay bud break in the spring.
• A treeline also provides protection from strong winds and helps protect tender shoots during spring growth.
  • Diagrams showing regional wind patterns in each month are available online for many areas across Minnesota. Use these diagrams to determine the direction and speed of prevailing winds.
• The selected location should also allow for air drainage (sloping ground). Avoid low-lying areas that can become frost pockets.

Soil

Kiwiberry grows best in well-drained, aerated, moisture-retentive soil that is rich in organic matter and slightly acidic to neutral (pH 5.5-7.5).

Mulch

Use a 4-inch-thick layer of mulch to retain moisture, regulate soil temperatures, control weeds, and encourage healthy root growth. In the spring, cooler soil temperatures beneath the mulch layer can delay budbreak and reduce the risk of spring freeze injury.

Compared with plants grown in bare soil, A. kolomikta grown under a thick layer of mulch tends to have a much more laterally extensive and denser fine root system. Many of these roots are distributed along the mulch-soil interface and can extend several feet out from the trunk. 

Recommended mulch materials:

• Wood chips
• Leaf mulch
• Corn stover

Kiwiberry vines need sturdy support for growth. The vine twists counterclockwise around support structures, and the vigorous growth becomes very heavy by mid-season. 

Vines can be trained to a pole or tree stake and then onto a trellis structure, such as a T-bar or pergola. Both T-bar and pergola trellis systems use high-tensile steel wire to support the vegetative canopy. 

T-bar system benefits

• Simpler - it can fit into the row structure of a larger diversified orchard and allow for some mechanization.
• Offers lower humidity which may reduce incidence of sooty blotch or flyspeck.

Pergola trellis structure benefits

• Higher fruit production with a lower incidence of berry rub marks.
• Easier harvest because the berries hang down from the overlying vegetative canopy.
• Maintains cool, moist soil conditions once the foliage canopy is established.
• Less weed growth because of the shade.
• Less suckering at the base of the trunk because of the shade.

New vines take four to five years to train for production. Vines with an established root system that need to be regrown and trained due to winter injury may take 1 to 3 years to train.

First growing season

• Transplant bare-root or container-grown vines early in spring, after the risk of frost has passed. 
  • This will allow the root system to become well-established before winter, and will promote vegetative growth the following year. 
• Most vegetative growth occurs in late spring to early summer. 
• Rapid growth in A. kolomikta ends earlier than in A. arguta.
• You can also plant dormant vines in the fall before the soil freezes. 

Second growing season

• In the spring, look for a thick and vigorous shoot that is about the thickness of a pencil emerging near the base of the trunk. 
• In late June, once this shoot starts to become woody, prune away all other growth to leave this single shoot. This will become the vine’s main trunk. 
• Loosely secure the shoot about 1 foot below the growing tip to the support stake, and allow it to grow for the remainder of the season or until it reaches the trellis wire above. 
• Pinch back the growing tip to encourage the development of a secondary side shoot. 
  • This second shoot should be located about two-thirds of the way up the trunk, near the trellis wire, to form a “Y” configuration at the split. 
• These will become the two main branches, or cordons.

Third growing season

• Cross the two cordons past one another so that one cordon arm of the “Y” goes from 2:00 to 10:00, while the other cordon arm of the “Y” goes from 10:00 to 2:00.
• As growth progresses, loosely tie the two cordons to the trellis wire. 
• Allow secondary shoots to emerge and grow out from the two cordons at uniformly spaced intervals of 8 to 12 inches. 
• Snip off any side shoots that appear lower down on the trunk. 
• Remove any vigorous “explorer shoots” that may emerge from the cordon since these will not produce flowers or fruit, and will crowd the canopy.

Fourth growing season

• Tie down the secondary canes to the support wires. 
• Specialized plastic vine buckle clips keep the shoots in place and prevent shifting. 
• Flower-bearing shoots are recognized by their closely-spaced buds. 
  • These shoots will bear the fruit crop (on female plants) the following year.

Fifth season and beyond

Prune out old secondary canes and tie down new secondary canes that formed during the preceding growing season.

Much of the vegetative growth occurs during the spring and early summer. Left unchecked, vines can grow into a tangled mess within a few seasons. In Minnesota, pruning is done in three seasons, and each season’s pruning is a little different.

Mid- to late autumn

Major pruning should be done at this time of year, once the soil begins to freeze. At this time, cuts on exposed wood will have the opportunity to dry out over the winter and reduce the potential for sap flow, or “bleeding” in the spring.

Late winter

It is ideal to do dormant pruning in late fall before heavy snowfall. But if pruning isn’t completed in late fall, it can also be done in late winter. Prune while the soil is still frozen. 

Pruning cuts made at this time of year will be subject to profuse sap flow, or “bleeding.” Prevent this by painting the cut areas with latex paint on a day when air temperatures are expected to remain above freezing for several hours so the paint can dry.

Spring and early summer

• Pruning at this time of year consists mostly of shearing, shaping, thinning and training to retain the desired plant architecture. 
• Kiwifruit plants store starch in the woody tissue of the vine canopy, and these starches are converted to sugar and translocated to the roots. 
• Any pruning that has not been done by mid-July should be delayed until the fall when the soil begins to freeze.

Supplemental watering will be needed during most Minnesota summers as drought-stressed plants are prone to smaller fruit, lower yields and premature berry drop.

Drought stress also makes plants much more susceptible to winter cold injury.

Fertilizing

We do not yet have specific soil recommendations for kiwiberries, but these general guidelines have been successful in research trials:

• Kiwiberry benefits from the application of fertilizer containing nitrogen and potassium. 
• Light applications should be broadcast around the trunk area from the spring, after the soil thaws, through late June.
• Most Minnesota soils have adequate phosphorus for plant growth. 
  • If a soil test shows a phosphorus deficiency, be sure to use a complete fertilizer. 
• Wood chip mulch generally does not tie up nitrogen unless the chips are incorporated into the soil during planting.
  • The woodchips will need to be replenished every few years to maintain a substantial cover.

• The berries begin to ripen in late July, and harvest may extend into late September and October.
• Cool night temperatures facilitate ripening.
• Immature berries are hard, opaque and glossy.
• As they ripen, the berries become dull, translucent and soft when gently squeezed.
  • In many A. kolomikta varieties, berries may also develop vertical stripes that are slightly yellowish.

• Once the berries start to ripen, it is time to pick them all.
• Like fuzzy kiwifruit, they are best eaten fresh and can be refrigerated for a week or two.
• To extend storage life, separate firm berries from soft ones, and remove all debris and damaged fruit.
  • Place the firm berries in special plastic fruit storage bags designed to absorb ethylene gas produced during fruit ripening. These can be found in many grocery stores and online.

Insect damage is rare on kiwiberry, though spotted wing drosophila may appear where overripe fruit is left on the vine or on the ground. Pick all the fruit during harvest, and remove any fruit that falls to the ground.

Rabbits and deer can injure the trunk and foliage. 

• Rabbits chew on the bark in fall and winter and may completely girdle the vine’s trunk.
  • Surround the trunks with fencing taller than the expected snow depth to protect from rabbit damage. 
• Deer may browse kiwiberry leaves throughout the growing season until the vines reach a height where the deer can no longer reach the foliage.

Aside from the root rots common to kiwifruit in poorly drained soil, there are no significant diseases to worry about when growing kiwiberry. 

• Prevent root rot by planting vines in well-drained soil, and be sure not to over-water.  
• Do not plant near black walnuts or hickories, as juglones in the soil derived from those trees will kill the vines. 

In late winter, the warmth of the sun, combined with the reflection from the snow surface, heats the wood tissue in the vine’s trunk. After sunset, the temperature cools quickly, refreezing this tissue. That rapid thaw-and-freeze cycle can kill cambium-layer tissue under the bark and cause trunk cracking, severely damaging the vine. This is called sunscald injury, and may be important for small-scale growers.

• All young vines are susceptible to sunscald because of their thin bark.
• A. kolomikta vines of all ages are susceptible because of their dark-colored bark that readily absorbs heat. 
• Mature vines of A. arguta develop a thick, shaggy bark. Once mature, these vines are less prone to sunscald and require less protection from winter sun. 

Ways to protect vines from sunscald

• Place a shade barrier on the south and southwest sides of the vine’s trunk to protect from sunscald if insufficient shade is available.
• Use plastic spiral wraps, split grow tubes, full grow tubes, or tree shelters around the trunk. 
  • If using split grow-tubes, place the split side on the north side of the trunk and secure it at the top to keep it from blowing off in strong winds. 

Spiral and full grow tubes or tree shelters can also prevent rabbit damage in winter. Split tubes do not protect the vines from rabbit damage, since the animals can access the trunk from the open side.