By: Mary H. Dyer, Credentialed Garden Writer
Seedless grapes are rich in flavorful juiciness without the bother of pesky seeds. Most consumers and gardeners may not give a lot of thought to seedless grapes facts, but when you stop to think about it, exactly what are seedless grapes and without seeds, how does a seedless grape reproduce? Read on for answers to those questions, and more.
If you’re concerned that seedless grapes are the result of some sort of genetic modification or weird scientific wizardry, you can relax. The first seedless grapes actually came about as a result of a natural (not laboratory-produced) mutation. Grape growers who noticed this interesting development got busy and grew more seedless grapes by planting cuttings from those vines.
How does a seedless grape reproduce? The seedless grapes you see in the supermarket are propagated the same way – through cuttings that produce clones of an existing, seedless grape variety.
Most fruits, including cherries, apples and blueberries, are produced in this manner. (Citrus fruits are still propagated the old-fashioned way – by seed.) Often, seedless grapes have tiny, unusable seeds.
There are many different types of seedless grapes, with seedless grape varieties available to home gardeners in nearly every climate across the country. Here are just a few:
‘Somerset’ tolerates chilly temperatures as far north as USDA plant hardiness zone 4. This heavy-bearing vine produces sweet grapes with an unusual flavor that is reminiscent of strawberries.
‘Saint Theresa’ is another hardy seedless grape suitable for growing in zones 4 through 9. This vigorous vine, which produces attractive purple grapes, grows well on a screen or arbor.
‘Neptune,’ suitable for zones 5 through 8, produces large, juicy, pale green grapes on showy vines. This disease-resistant variety ripens in early September.
‘Joy’ is a blue grape that tolerates rainy weather better than many varieties. Joy is ready to harvest relatively early, ripening in mid-August.
‘Himrod’ produces clusters of sweet, juicy, golden grapes that ripen in mid-August. This variety performs well in zones 5 through 8.
‘Canadice’ produces compact clusters of sweet, firm, dazzling red grapes from mid-August through September. This mild-flavored variety is suitable for zones 5 through 9.
‘Faith’ is a reliable producer for zones 6 through 8. The attractive blue, mellow fruit typically ripens very early – in late July and early August.
‘Venus’ is a vigorous vine that produces large, blue-black grapes. This hardy vine prefers zones 6 through 10.
‘Thomcord’ is a cross between familiar Concord and Thompson grapes. This heat-tolerant vine produces fruit with the richness of Concord and the mild, sweet flavor of Thompson.
‘Flame,’ a good choice for warmer climates, this grape variety thrives in zones 7 through 10. The sweet, juicy fruit ripens in August.
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Grape breeders have responded to consumer preferences for seedless grapes with the development of numerous improved varieties. The seedless trait in grapes was originally derived from cultivars of ancient origin such as Thompson Seedless and Black Monukka. Most seedless grapes suitable for the eastern United States are descended from crosses with these two cultivars. 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 (Table 2), although they are much hardier than their seedless parents. More recently named seedless cultivars (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. Promising selections from the New York program are available for test purposes only.
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 their seed coats. Climate is also known to affect seed trace size. Occasionally the seed traces in some seedless grapes are large enough to be bothersome to consumers. Notes on seed remnant sizes are given for varieties in which problems exist.
Marquis (Plant patent 11,012) was named and released at Geneva in 1996. Clusters are very large, medium compact, and attractive, with large, round, yellow-green berries (3.5 - 5.0 gm/berry). Texture is melting, and the taste is very flavorful. 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. Giberrellic acid treatment is not recommended, but well-timed cluster thinning and cane girdling can increase berry size and improve cluster compactness. Vines are moderately hardy, medium in vigor and productive.
For more information, see the Marquis Release Bulletin.
Neptune (Plant patent 12,302), a 1998 release from the University of Arkansas, is a yellow-green seedless grape cultivar of moderate vigor. The clusters are large and very showy, but productivity is moderate. Flavor is mild and fruity, while fruit texture is firm with a relatively thick skin, similar to many eastern seedless grapes. There is relatively little experience growing Neptune in New York. It is reported to be more winter hardy than Venus. Maturity was mid- to late-season in 2004. Berry weight = 3 g in Arkansas
Venus, also from the University of Arkansas, is a vigorous and productive blue-black seedless grape. The medium-large clusters ripen early, producing large berries with mild labrusca flavors. In New York, the seed remnants are hard and noticeable, and fruit rot has been a problem at harvest. Fruit quality is only fair. Cluster weight = 0.60 lb. Berry weight = 2.9 g
Seeds are only one way that plants are reproduce. Plants can also spread by growing bigger and spreading out across the ground. At some point the plant becomes so big that different parts of it are capable of growing by themselves. The plant may then split or the mature parts simply fall off. These off-spring are usually called "clones," because they are genetically identical to their parent plants. Classic examples of these clones include familiar garden plants like strawberries (they have long roots called stolens that spread out from existing plants). Another special way of reproducing plants is called grafting. When plants are grafted the green top of one plant is combined with the living roots of another plant. This process can establish plants that might not be able to reproduce on their own. Nuts, apples, and stone fruits are often grafted (sometimes you can see a strange line near the base of the tree where the width of the tree changes or maybe the bark is a different color). So, back to your watermelons and grapes.
Given those options, if you were a farmer how would you grow more?
Hint: You've probably already got a whole field full of healthy watermelons and grapes to work with.
How do you plant seedless fruit? You don't. Plants that produce seedless fruit ("sterile" plants) do not occur in nature since they cannot reproduce. Scientists have created certain special varieties of commercial fruit to grow without seeds (e.g. oranges, grapes) or with smaller, reduced seeds (bananas, "seedless" watermelons) in order to make it more convenient for humans to eat them. However, these varieties must be specially cultivated since they cannot be re-planted from seeds.
For seedless grapes, new plants must be made from existing ones. The easiest method involves slicing the stem of an adult plant diagonally and cutting sections from it.One end of each cutting can then be dipped in a rooting hormone. (Yes, plants have growth hormones! Rooting hormones stimulate the production of roots.) The cuttings are planted and eventually grow into new plants that produce fruit. Grapes from seedless plants are small, and must be treated with plant growth hormone in order to ripen to normal size. The process of growing seedless grapes is a form of asexual reproduction, as the new plant is basically a genetic clone of the original parent plant. Some seedless grape varieties have been grown this way since Roman times (a grape plant that is 2,000 years old)! Wild grape plants reproduce sexually, by a process called pollination. In sexual reproduction, male gametes combine with female gametes to produce a new organism which has half of its genetic identity from the mother and half from the father. Find a book about general plant biology ("botany") or
look on the web and try to answer these questions: What parts of plant flowers contain the male gametes (pollen)? What parts contain the female gametes (eggs)? How does pollination occur (that is, how does the pollen make it to the egg)?
In order to create seedless watermelon plants, normal seed-producing plants which have 2 sets of chromosomes are pollinated with pollen from plants that have been engineered to have 4 sets of chromosomes. The resulting seeds produce plants ("hybrids") that have 3 sets of chromosomes. These hybrids are sterile, which means they produce seedless fruit. In this way, a seedless watermelon can be grown from
Scientists are working on new ways to produce seedless watermelon, tomatoes, eggplant, cherries, cucumbers and green peppers.
Grapevines will become stunted if weeds and grass are allowed to grow at their base, so take care to weed the area around your vine carefully. Use mulch to help contain weeds and retain moisture. The University of Arizona cautions against fertilizing during the first year.
All grapevines need a support system. In your home garden, fences, single stakes and arbors are great options for training your vine. Pruning a grapevine is an encyclopedic topic, but here's a summary: Your goal is to develop a straight trunk, so in the first year, select a single, strong shoot and tie it to a stake. Then remove all other shoots. It will grow quite a bit in its first season. If you are training it on a fence, cut it back just below the top of the fence. New canes will form below the cut next spring, and you can train these sideways along the fence. If you're training it instead on an arbor, you want the cane to reach as close as possible to the top of the arbor, so it can begin to branch there. Each year, you'll prune your vine back during dormancy, just before bud break in the spring. Regular pruning will support the production of a good grape harvest.
Begin a regular fertilizer program in your vine's third year, applying about 10 ounces of 10-10-10 fertilizer per vine each year, and doubling this amount every three years for six years. Apply that same amount of fertilizer each subsequent year.
Thompson Seedless grapes are susceptible to a few typical grapevine diseases, in particular, a fungus Botryosphaeria canker the vine is also moderately susceptible to powdery mildew, reports University of California at Davis. But the real problem for Thompson Seedless growers is Phomopsis cane and leaf spot, formerly known as "dead-arm." This is particularly a potential problem if the spring was unusually wet. Diseased shoots may have hampered growth, and in the winter, infected canes can look whitish or bleached. Use a foliar fungicide if your vine develops these symptoms.
Grapes not used to make wine are known as table grapes (Vitis vinifera), and seddless varieties are the most popular. Supply the vine with a sturdy trellis or arbor on which to grow, lots of sunshine and acidic soil and you’ll be repaid with a bounty of green, yellow, purple or red seedless grapes. Cultivars to consider include Thompson (V. vinifera “Thompson Seedless”), hardy in U.S. Department of Agriculture plant hardiness zones 7 to 10 Concord Seedless (V.vinifera “Concord Seedless”) hardy in USDA zones 4 through 9 and, if you prefer red grapes, Flame (V.vinifera “Flame”) hardy in USDA zones 7 through 10. Wait until the vine is dormant and the buds are beginning to swell in the spring to take the cutting.
Fill the planting pot with potting soil and slowly run water over it until it is evenly moist. You may need to stir the mix to check for dry spots.
Select woody stems about the same diameter as a pencil. Use pruning shears to snip 12-inch pieces that include three buds. Make a diagonal cut at the tip that grew the furthest from the main branch as soon as you remove the stem from the vine.
Stick the flat end of the seedless grape cuttings into the soil far enough so one bud remains above the surface.
Place the pot in a sunny window and keep the soil moist while the cuttings root. This should take from three to six weeks. New foliage lets you know that the cuttings are producing roots.
Continue keeping the soil slightly moist and transplant the seedless grape cuttings outdoors at the end of the summer.
Seedless grapes are easy-to-grow and are healthy, easy-to-eat snacks. Learn what makes grapes seedless and find tips on growing seedless grapes.
Grapes are the "queen of fruits" in many parts of the world. They are a treasure trove of anti-inflammatories, vitamins, minerals, and nutrients – including antioxidants, found in grape skins. They're low in fat, calories, and are cholesterol-free, so there's no guilt when you're snacking on grapes! Seeded grapes and seedless grapes can both be grown at home, but growing seedless grapes is more popular for how easy they are to grow as well as harvest and snack on.
1. Somerset Grape | Seedless • Self-pollinating • Color: Red/purple
A unique, strawberry-like flavor. Bears heavy, compact clusters of medium-sized table grapes that are good for fresh-eating and making jelly. Vigorous, disease-resistant, and cold-hardy vines. Fruit ripens in August.
2. Gratitude Grape | Seedless • Self-pollinating • Color: White/green
Exceptionally crisp and juicy. Bears gorgeous, tight clusters of bright, sweet-tart, crack-resistant, thin-skinned fruit. Developed at the University of Arkansas. Fruit ripens in late August.
3. Thomcord Grape | Seedless • Self-pollinating • Color: Blue/black
The best of both worlds! Offspring of parents: Thompson and Concord. Fruit retains the rich flavor of Concord and the light sweetness of Thompson. Vines are heat-tolerant. Fruit ripens in August.
Some seedless grape varieties may develop tiny seeds/vestigial seeds or seed remnants/traces depending on the variety and the climate in which they are grown. While some seed development is attributed to cross-pollination by seeded grapes, this is not so likely.
Dig the hole. Assess the size of the vine's root system and dig a hole approximately twice as large. Place the grapevine in the hole, spreading out the roots, and back-fill with soil until the hole is three-quarters full. Water to settle the soil. Finish filling with soil and water again.
Prune after planting. Cut back the plant to two buds. These should be encouraged to grow in opposite directions along the trellis. Each successive year, prune off old/dead canes to leave room for the most vigorous canes.
Water as needed. New plants need more water than established vines water weekly for the first year, especially in hot/dry spells.
*Once you decide to grow your own seedless grapes, remember that the vines require a support system – like a sturdy fence, arbor, or trellis – as they grow and mature. The support should be in place before planting, or very soon after.
» Watch this great "DIY" video from the Oklahoma State University: Building a Grape Trellis. If you don't have room to turn your backyard into a vineyard, The Fruit Gardener's Bible book has wonderful instructions on growing grapes in containers – perfect for small-space gardening!