Frost grape (Vitis vulpina) is a species of perennial grapevine found throughout the United States and Canada. Frost grape is also called the winter grape, fox grape, and the wild grape. This species is used commercially for making wine.
I. Appearance and Characteristics
Vitis vulpina (with common names frost grape, winter grape, fox grape, and wild grape.) is a North American species of herbaceous perennial vines in the grape family. It is widespread across most of the eastern and central United States as well as the Canadian Province of Ontario.
The genus name Vitis comes from the Latin word for “vine” and the species name vulpina comes from the Latin word for “fox-like” or belonging to a fox. It is believed that foxes were attracted to this type of grapevine, and Linnaeus used the term vulpina to differentiate these smaller wild grapes from the other American known grapes. The more common name, frost grape, refers to the fact that this otherwise acidic/tart-tasting grape becomes more desirable and sweet once it is exposed to a frost. II. How to Grow and Care
Vitis vulpina has a relatively long lifespan with a moderate growth rate. Typically the vine will reach a maximum height of about 83 feet. Contrary to the name “Frost Grape,” the plant does not do well in cold temperatures below -23 degrees F. The only benefit of the frost on the grape is further ripening of these grapes between the months of September and October. The berry (grape) is round and very tart/acidic, becoming sweet after a frost due to a drop in acid levels as the grape decomposes.
Along with the ripening of the grapes in colder months, the leaves eventually fall off as the plant enters the dormant stage. Grapes tend to shrivel up on the vine, turning into raisins if not harvested before meteorological winter. The shriveled grapes are advantageous for animals looking for food during these months.
The grape vine can be either monoecious or diecious, with flowers appearing in May to June. The flowers are arranged in compound panicles with 5 yellow petals, 5 sepals and 5 stamen (floral number is 5). The leaves are arranged alternately with a cordate shape. Venation is palmate. Unlike other wild grapes there are no tufts of hair present on the leaves. Tendrils appear every third leaf oppositely are reddish in color and used for growth along surfaces. The grapes are tiny and dark purple.
It is most commonly found in moist or dry soils in woods, flood plains, and ravines. Due to its known ability to climb, the vine is often used along fences and trellises for ornamentation.
II. How to Grow and Care
Sunlight
Frost grape thrives best in full sun conditions where it can receive direct and intense light for the majority of the day, which is essential for its vigorous growth and fruitful production. While frost grape is capable of tolerating partial sun, less than optimal light exposure may result in reduced growth rate and smaller yields.
The plant exhibits adaptive traits to manage light fluctuations, such as leaf angle and orientation adjustments to optimize light absorption. For outdoor cultivation, frost grape should be planted in areas with clear exposure to sunlight, avoiding shaded regions that might impede its development.
Temperature
Frost grape needs a growing season of at least 150 days, with a winter temperature higher than -32 ℃. Hardiness varies depending on variety; some require extra protection in cold winter environments. Ideally, frost grape needs dry heat during the day, with cool, humid nights.
Watering
Originating from the moist woodlands, frost grape thrives in environments that mimic the consistent moisture of its native habitat. This species exhibits a preference for regular hydration but is adaptable to brief periods without water. Following its natural rhythm, frost grape benefits from watering every week to maintain its vitality. Cultivated primarily outdoors due to its growth habit, frost grape shows resilience in various climate zones and can adapt its water usage accordingly during different growing seasons.
Soil
Frost grape requires deep soil with good drainage; ideally, a sandy loam. The optimum pH value ranges from 5.5 to 7.0. Make sure that water does not accumulate around the plants after rainfall.
Fertilizing
For frost grape, fertilize in early spring with balanced nutrition fertilizer, like 10-10-10, to support new growth. During the growing season, apply a half-strength, more phosphorus-rich mix to promote fruiting every 4-6 weeks. Avoid excess; 1-2 cups per vine is ample. Seasonal adjustments: reduced feeding in fall, none in winter. Use granules around the base and water thoroughly to prevent root burn. This regimen ensures vigorous vines and bountiful fruit.
Pruning
Pruning your frost grape is very important to maintain growth and prevent diseases and pests.
Bud picking and pinching. As soon as mature plants start to bud, keep only one strong bud on each node of the strong branches, picking off any buds. Remove overgrown or stunted branches, axillary shoots, and tendrils as soon as possible to facilitate ventilation and transmission of light. New frost grape shoots must be pinched so that only 4-8 leaves remain above the spike.
Flower thinning. The number of flower spikes is usually determined according to the species and the weight of the spike. For small-spike species of frost grape, 2 spikes can be left on each fruiting branch. For medium-spike species, 1 spike can be left on each fruiting branch. For large-spike species, no spikes should be left on the new vine near the main vine.
Flower-spike thinning should be carried out before flowers start to bloom to avoid excess nutrient consumption. Remaining spikes need to be pinched off by 1/4 of the length of the spike tip. The secondary and tertiary spikes that grow later can be thinned in time.
Winter pruning. For newly planted seedlings in their first two years, all axillary shoots should be cut off to keep the trunk strong. Only the trunk and leaves directly attached to the trunk should be left. Once the trunk grows 91 cm tall, the top tip should be pulled horizontally and tied to an iron wire at a higher level.
After the first two years, select the robust fruiting branches close to the trunk for cutting back. Each pruned spur should have 2 or 3 buds. After new shoots sprout in the spring of the following year, the shoots at the upper part of the plant are the ones that will bear fruit. Then the rest of the branches can be cut off.
When you winter prune the following year, a strong branch near the base of the trunk should be selected for short-tip pruning as a new fruiting branch, ensuring that 2 or 3 buds are once again retained. Repeat in this way, and robust fruiting branches can be kept while the year-by-year outward movement of fruiting parts can be prevented. When a wound caused by winter pruning is larger than 1 cm, a protective agent should be applied to prevent bacteria infection. Any cut branches and tendrils should be burned in bulk.
Propagation
Frost grape can be propagated through softwood cuttings or layering in the spring or summer. Propagation difficulty is moderate, but signs of successful propagation include the development of roots and new growth. To ensure success, use well-draining soil and provide adequate water and nutrients.
Transplanting
The ideally charming seasons to transplant frost grape are late winter to early spring (S3-S4), a time when the plant is in dormancy. The location for frost grape should have well-drained soil and full sun exposure. Always handled with extensive care, ensuring no damage to the roots during the transplant process.
Repotting
Refresh the vigorous climber frost grape every 2-3 years in early spring before rapid growth. Select a large, sturdy container to accommodate its extensive root system. Post-repotting, ensure frost grape has ample support for vertical growth. Maintain consistent moisture and avoid disturbing the roots for swift recovery. Adhering to these guidelines promotes robust vines and bountiful fruiting.
III. Harvesting and Storage
To ensure the best flavor, pick only fully ripe fruit. The simplest and most reliable way to confirm maturity is by tasting. Clusters can then be cut off with scissors and stored. Berry quality declines rapidly in later stages of maturity, and rotten fruit can damage the frost grape.
