Cold-climate grapes

About cold-climate grapes

Cold-climate grapes include a range of varieties that have resulted from crossbreeding multiple grape species to create hybrid grapes suitable for production in cold-climate regions.

Vitis vinifera is a grape species well-known for producing wine grapes, such as Merlot and Cabernet. However, V. vinifera varieties are not cold-hardy enough to thrive and survive in cold-climate regions such as Minnesota and the Upper Midwest without interventions, such as burying vines to protect against extreme winter cold.

Some native grape species that grow in Minnesota and throughout North America are hardy enough to survive the colder winter conditions here, where extreme winter temperatures can drop below -30 degrees F.

Some grape production and breeding efforts took place before the University of Minnesota initiated its breeding program in the early 1900s, which paused during Prohibition.

A number of varieties were bred through the University’s collaboration with private breeder Elmer Swenson, who bred grapes from the 1940s until the late 1970s.

Today, the University of Minnesota cultivates seven different wine grape varieties: Marquette, Frontenac, Frontenac blanc, Frontenac gris, La Crescent, Itasca, and Clarion. The program has released several table grape varieties (Swenson Red, Bluebell) and is continuing to breed new varieties suitable for survival in USDA Growing Zone 4 and warmer Upper Midwest regions.

In addition to the University’s breeding program, other programs have developed cold-climate varieties, such as Petite Pearl and Verona.

Fruit characteristics

There is significant variation in cold-climate grape variety fruit cluster attributes (size and shape), berry qualities (flavor, color, aroma), and growth habits (tendency to grow upright or trail). These differences often result from a grape variety’s background or heritage and the grape species that contribute to its unique genetics. 

Grape and wine characteristics specific to a given variety are what give way to its typicity, or how true to type a grape or wine is to its varietal type.

Terroir refers to grape and wine characteristics influenced by specific site features, such as soil composition, topography, and climate. 

Cold-climate grapes are not grafted

Because cold-climate grape roots have inherent resistance to phylloxera (a pest that can damage non-resistant grape roots), they are not grafted and do not require the use of rootstock, unless special circumstances exist. This is an advantage for cold-climate vineyards because they can be easily retrained after a polar vortex event that causes severe damage to older vine parts.

Pest management

Due to the humid conditions in the Upper Midwest, a pest management program is needed to prevent diseases such as black rot (Guignardia spp.), phomopsis (Phomopsis viticola), downy mildew (Plasmopara viticola), and anthracnose (Elsinoe ampelina).

Some insect pests can be a concern for growers in the Upper Midwest, but grape diseases are usually of much greater concern. Insect pests that are problematic to grape production in the Upper Midwest include grape flea beetle (Altica chalybea), foliar grape phylloxera (Dactylosphaera vitifoliae), Japanese beetles (Popillia japonica), and harvest-disrupting insects like yellow jackets (Vespula spp.) and multicolored Asian lady beetles (Harmonia axyridis). 

Bud-break and harvest windows

In Minnesota, many varieties begin to grow in May, and the earliest-ripening varieties are harvested in mid-August, while later-ripening varieties may hang until mid-to-late October.

Growers are encouraged to track fruit ripening using tools such as refractometers to estimate sugar content, and pH meters and titrators to measure total acid concentration. 

When grapes are harvested for wine, single varieties are usually harvested all at once. In contrast, fresh-eating grapes can be harvested as clusters ripen and meet specific ripening goals, including visual inspection of fruit color.

Wine production styles also vary for cold-climate grapes.

Grapevine anatomy and terminology

Grapes are botanically classified as vines. They climb as they grow and use tendrils to hold onto support structures, such as trellises in vineyards or trees and other plants in the wild.

Their tree-like shape, evident in many vineyards, results from years of training the grapevine into that shape, as older vine parts become thicker with each growing season.

Mature grapevine root systems are extensive compared to those of other fruit crops. They can grow deep below ground as the vine ages, making it tolerant of moderately competitive ground covers.

Young grapevines benefit from attention to competitive vegetation and irrigation as they become established. 

Common terms for grapevine anatomy

• Shoot – current season’s growth. Produces leaves, tendrils and clusters.
• Cane – a mature shoot after one growing season. Shoots emerging from buds on canes can produce fruit.
• Fruiting zone – region where fruit clusters exist.
• Cordon­ – wood older than two years. The “arms” that support the fruiting zone.
• Spur – a cane pruned back to two to five buds. Spurs exist in the fruiting zone and can “stack” on top of older spurs from previous years.
• Dormant bud – composed of overlapping immature leaves and clusters. Where shoots originate.
• Cluster – the compound inflorescence that blooms and sets fruit.
• Watersprouts – shoots originating from latent buds from the trunk, cordon, or other older woody parts of the vine.
• Suckers – shoots originating from the trunk crown or base.
• Trunk – semi-permanent or permanent structure providing support for the arms and canopy.
• Head – the grapevine trunk top where the cordons or arms and trunk meet.

Nodes, internodes, and compound buds:

Nodes are regions along shoots and woody canes (one-year-old shoots) where leaves are or have previously attached. On a shoot, each node also contains a lateral (branching) shoot, tendril, and developing compound bud (on left) that will produce shoots and, potentially, clusters the following growing season.

The internode is the space between two nodes.

• Very short internodes are usually found on smaller, weaker shoots and canes.
• Excessively long internodes are characteristic of bull canes or shoots.
• Long internodes can be problematic for establishing vine parts like cordons, as the distance between spurs can affect the vines’ total yield.
• Healthy, moderately vigorous shoots and canes have internodes that are about one adult fist long.

Compound buds contain three or more separate buds, in which the largest, primary bud and secondary bud give way to shoots that produce fruit. Non-fruiting buds may take over when cold damage occurs in the primary and secondary buds, helping the vine survive to the next season.