One high-value horticultural crop that is worthy of trial is seedless table grapes. These grapes are in the same family that the seeded ones are in: Vitis labrusca. Most people are familiar with the Concord, Niagara, Catawba and Delaware. The seedless varieties are available in the same colors.
Dr. Bruce Reisch, a grape breeder at Cornell University, has worked with several of the seedless varieties and commented:
“Grape breeders have responded to consumer preferences for seedless grapes with the development of numerous improved varieties…Because the trait originated in cultivars not suitable for surviving the cold temperatures of New York winters, many seedless varieties are not sufficiently winter hardy in New York, although they are much hardier than their seedless parents. More recently named seedless cultivars such as Canadice, Einset Seedless, Reliance and Vanessa represent a distinct improvement in cold hardiness. Breeding programs in New York, Ontario, Arkansas and elsewhere continue to produce seedless selections with improved hardiness and quality.
“A wide range of flavors and appearances are available among the seedless table grapes. Vitis labrusca is the parent species of many of the flavorful eastern grapes. The degree of seedlessness varies greatly among seedless grape varieties. Most seedless grapes have vestigial seed traces that range in size from very small to large and noticeable. Seed traces in berries of the same variety may vary greatly in size and in the hardness of seed coats. Climate is also known to affect seed trace size.”
A study was initiated in 2005 to look at the possibility of growing seedless, fresh market table grapes (Vitis labrusca) in the northern Piedmont of North Carolina. Research done on these grapes was scant and to my knowledge, no one had grown these grapes on a commercial scale in the North Carolina Piedmont.
I decided to put out a replicated cultivar trial, consisting of 14 different table grapes on one acre, which were varieties from the breeding programs at Cornell University and the University of Arkansas to see what cultivars would perform best in the Piedmont. This consisted of planting 360 vines on one acre. A randomized complete block design with five plants per plot and five replications was used. Vines were spaced 10 feet between vines in the row, 10 feet between rows and were planted on May 18, 2005 in a clay loam soil.
Trial cultivar descriptions
Time of ripening of each variety is noted for Oxford, NC.
- Marquis is a cross of Athens x Emerald Seedless and is a white seedless grape with excellent mild American flavor. The berries are large, often 3.5-5.0 g/berry, with a juicy, melting texture. Clusters are large and attractive, while the vines are very productive. Ripens Aug. 2 – 10. Ripe fruit holds well on the vine, with the flavors going from a mild fruity flavor when first ripe, to a stronger labrusca flavor two weeks later.
- Himrod is produced from a cross between Ontario and Thompson Seedless and is the most successful table grape released from the Cornell University grape breeding program. It produces large bunches of white seedless grapes with excellent, honey-like flavor and melting, juicy texture. The clusters are loosely filled (cluster weight = 0.36 lb., berry weight = 2.1g). Ripens July 20 – 27.
- Lakemont was also produced from the same cross as Himrod but has a milder flavor and more compact clusters of small to medium-sized berries. Cluster thinning prevents over cropping (cluster weight = 0.48lb., berry weight = 1.7g). Ripens July 26 – Aug. 3.
- Interlaken is a sister seedling of Himrod (same parents) with seedless green to golden berries. The clusters are medium sized and compact with small, white berries that ripen very early. Cluster weight = 0.27lb., berry weight = 1.5g.
- Einset Seedless resulted from the cross of ‘Fredonia’ x ‘Canner’ (‘Hunisa’ x ‘Sultanina’). The berries are oval and bright red with a light waxy bloom (powdery covering on the fruit). The medium soft seed remnant is not usually noticeable. Berries are medium sized (cluster weight = 0.32 lb., berry weight = 2.3g). The flavor is fruity with a mild note of labrusca and sweet strawberry-like taste. Ripens July 20 – 26.
- Vanessa was developed by the Horticultural Research Institute of Ontario, Canada and is a red dessert grape of excellent quality. The seed remnant is usually large and soft when noticeable. Berries are medium in size on medium, well-filled clusters. The flavor is mild and fruity, and berry texture is firm to crisp. The fruit quality is among the best of the red seedless types. Ripens July 20 – 27.
- Canadice produces medium, excessively compact clusters with small red berries (cluster weight = 0.50lb., berry weight = 1.6g). Ripens July 26.
- Reliance comes from the University of Arkansas and produces large clusters of round, red, medium-sized berries. The skin is tender and the flesh is melting in texture, with a sweet labrusca flavor. Cold hardiness is among the highest of the seedless varieties (cluster weight = 0.62lb., berry weight = 2.3 g).
- Suffolk Red produces medium to large clusters of mild-flavored red berries. The clusters are loose (cluster weight = 0.32lb., berry weight = 2.7g). Ripens Aug. 10.
- Mars is a release from the University of Arkansas, and is a vigorous, blue seedless grape. The flavor is mildly labrusca and the berries are slipskin (having a tough skin which separates readily from the pulpy flesh). Clusters are medium-sized, cylindrical and well filled. A very high-yielding cultivar (cluster weight = 0.40lb., berry weight = 3g). It has a long ripening season from July 27 to Aug. 10.
- Venus, also from the University of Arkansas, is a vigorous and productive blue-black grape. The medium-large clusters produce large berries with mild labrusca flavors. (cluster weight = 0.60 lb). Berry weight = 2.9g. Seed traces may be noticeable. Ripens July 20 – Aug. 3.
- Glenora produces medium-sized blue berries. The clusters are extremely loose. The taste is very bland and not as flavorful as the other varieties. Ripens July 20 -27.
- Jupiter was released from the University of Arkansas in 1998. It is an early maturing reddish-blue to blue variety when mature. It has large, firm, non-slipskin berries on medium-sized clusters. Fruit has a distinct Muscat flavor. (cluster weight = 0.5lb., berry weight = 5g). Ripens July 20 – 27.
- Concord Seedless is similar in flavor and texture to Concord. The clusters and berries are much smaller than those of Concord. Ripens Aug. 10. Productivity is erratic, due to its uneven ripening under hot temperatures. When grown in hot climates, the berries produce seeds, hence, it is not seedless.
During 2005 and 2006, the vines were trained and pruned to prepare for a first harvest in 2007. Despite a freeze on Easter weekend in 2007, which killed the primary buds, the secondary buds emerged and produced a small crop. In 2008, hail destroyed most of the grape crop so yield data was not taken. In 2009, a much larger crop was harvested. Yields are presented in the table provided.
All of these varieties are easily sold at farmers markets and can bring prices over $4/lb. Yields can approach 4,000 lbs. per acre or more.