by Jack Ruttle The news in blackberries, with the introduction last year of two new varieties -- Navaho in Arkansas and Waldo in Oregon -- is that there are now thornless varieties for all but the very coldest parts of the country. These new plants will surprise anyone who is familiar with the wild blackberries that colonize the roadsides of America throughout zone 5 and southward. Besides being thoroughly smooth-stemmed, the new varieties have lost the weedy tendency to throw up vigorous suckers in all directions. And their fruit is large and is borne abundantly. A single plant can yield 20 pounds of fruit; two plants can keep a family of four in berries for nearly a month. The sight of one of these plants literally dripping with big, glossy black fruits from the top of the trellis to the ground is truly astonishing. These newer varieties are sure to make blackberries as popular with gardeners as are strawberries or raspberries. The older varieties of blackberries are not ideally suited to today's smaller gardens. To raise them you need space where they can grow in a hedgerow or as a large bush. The arching canes get big, eight feet or taller, and are heavily armed with long, recurved thorns. They aren't plants you want near walkways or lawns. Pruning them takes thick leather gloves and loppers, and picking them without getting scratched or caught takes considerable practice. The more civilized thornless varieties have changed all that. Their stems are glossy and smooth, without a vestige of prickles. These blackberries are even easier to handle than red raspberries, though the plants are much taller. With summer pruning to keep them in bounds and a simple trellis, you can now grow any of the thornless varieties in ground space as small as eight feet long by 1 1/2 feet wide. If space is not a limiting factor in your garden, however, you may still want to plant some of the modern thorny varieties like Shawnee. Most of them require no trellising, and all are tops for flavor. Moreover, among the thorny varieties, you'll find both the most cold-tolerant and heat-tolerant kinds. To know which blackberries -- thornless or not -- might grow best for you, it's helpful to know a little about how these modern varieties originated. An American tale Blackberry cultivation was essentially invented in the United States a little over a hundred years ago, when a few people began naming superior wild plants and growing them in a controlled way. For a long time some of those wild selections dominated blackberry culture. So as you might expect, blackberries are well adapted to the climate, insects and diseases of North America. Still, regional differences have come to limit which particular varieties will grow best where you live. And although breeding efforts are scrambling the gene pool pretty thoroughly, you can think of blackberries as falling into four distinct groups. There are erect varieties for the North, erect varieties for the South, trailing varieties for the west and thronless varieties for all three regions. For the North, Chester and Hull are the two best cold-hardy thronless blackberries, both hardy to about -10oF. Chester and Hull began life in central Illinois, and were rigorously tested for over a decade before being released from the USDA station in Beltsville, Maryland, in the early 1980s. Both varieties are less acidic and have about 50% more sugar than the first generation of thornless varieties -- Smoothstem, Black Satin and Thornfree -- and as a result are much sweeter. Of the throny cold-hardy varieties, Darrow is the most cold resistant, fruiting after winters of -20oF. In the South, the blackberries that have been developed are notable for their heat tolerance and for their resistance to such diseases as orange rust, which sometimes devastaste varieties developed in other regions. Navaho is a thornless variety developed by Dr. James Moore in Arkansas, and so far the only erect, self- supporting thornless variety. The other varieties from the Arkasas program -- all of them have Indian names (Cherokee, Cheyenne, Comanche an so on) -- are thorny and notable for very high yields and large, high-quality fruit. As an added bonus, most are tolerant to temperatures as low as -10oF, so can be grown in the Midwest as well. In the Deep South, where a short winter-chilling period can be a problem, the thorny variety Brazos is the best bet. Floragard and Gem are other good thorny varieties for the heat. In the mild coastal areas of the west (zones 7,8,9), you can grow almost any blackberry you want. However, the traditional varieties in the west are a bit different. These are trailing, moderately thorny varieties that must be trellised. They ripen a month or more before varieties like Chester, Hull and Navaho. And they have a different, delectable flavor, perhaps derived from a combination of the wild trailing Pacific Coast blackberry and the red raspberry, which several of the varieties have in their heritage. The new introduction Waldo is completely thornless and ripens about a week later than the throny varieties. The favored throny varieties are Olallie and Marion, both introduced by Oregon breeders in the 1950s. These varieties suffer winter damage to the canes at temperatures below 10oF and die back at 0oF. Some, like Olallie, are occassionally grown in the southeast, but they can be troubled with disease there. Knowledgeable blackberry growers agree that the modern, post- 1940s, varieties have superseded the older varieties in all respects. They'll advise you, however, that if a recommended variety does poorly for you to try another before quitting on blackberries. Regional vagaries of climate or disease can affect everything from survival to fruit flavor. Ollalie, for example, develops much better taste in California than it does in its home state of Oregon, and no one knows quite why. Bringing in the berries After you've determined which varieties are your best bet, growing them will be relatively easy, provided you buy certified virus-free stock. Viruses can cause the plants to decline in productivity, and with thriving populations of wild blackberries all over the country, the chances for infection are high. For the same reason, don't plant your berries where bramble fruits have grown before and eradicate wild blackberries within 50 yards, if practical. The sweetest berries will develop in full sun, but you'll get good fruit with a half day or more of sunshine. The plants are not fussy about soil as long as it's well drained. A one- to two-inch mulch of decomposed or shredded leaves will keep the soil moist and provide all the fertility the plants need. Space erect varieties three feet apart in the row. Suckers arising from the roots will quickly fill the space between them. Trailing types don't sucker, but as the plants age new plants may form close to the crown. Space those plants five to 10 feet apart in the row, depending on the vigor of the variety. Fruiting starts the year after planting. Like their Rubus relatives the red and black raspberries, the long-lived roots of the blackberry produce biennial canes that grow one year, fruit the next, then die. You can cut out canes any time between the final harvest through the dormant season. Small blackberries are tricky to pick because they look perfect before they are fully ripe, though they're still very bitter at that stage. Wait to pick until the berries fall easily into your hand. Some varieties turn from bright and shiny to a dull luster when they're ready. High-wire action Erect blackberrries grow and bear fruit very differently than the trailing types. (Thornless blackberries, with the exception of Navaho, grow like the trailing types.) Erect varieties don't really need a trellis, though if you're trying to keep them within bounds a trellis can make it easier. The traditional practice is to let them form a thicket. Late in their first growing season, as the canes reach their full height, erect blackberries begin producing side branches from the top half dozen or so leaf axils. All the fruit next year will arise from shoots produced on these side branches. In other words, they produce all their fruit relatively near their extremities. So if the variety produces very long canes, the weight of the crop -- especially the newest heavy-yielding varieties -- can pull the canes toward the ground, compounding the blackberry's space-hungry nature. The simplest solution is to prune out the top of the canes in the first season when they reach about 48 inches. The ideal is to clip three to five inches off the tip. This forces the side shoots to develop at a more convenient height, and makes a more self- supporting plant. Since the side shoots begin developing so early in the season, they can get quite long -- perhaps three feet -- by the time autumn shuts things down. Left to themselves, these will form the next year's fruiting shoots at the half dozen or so buds nearest the tip, and the weight can pull the side branches down. By cutting each side shoot back to 18 inches during the dormant season, you'll encourage the branch to flower and fruit along its full length. If you're growing erect blackberries in a very small space, you can tie each cane to a single wire strung 40 inches above the ground, and prune off all side shoots except those growing in the direction of the wire. Though you sacrifice potential fruit, this creates a flat, narrow row of blackberries that intrudes as little as possible. You'll also have to cut root suckers diligently. All erect blackberries spread by sprouting from their roots, and strong shoots can spring up at surprising distances from the original plant. Navaho is the only thornless variety that grows with the erect habit. It does not produce suckers as readily as other thorny erect varieties, but it will fill the row just fine when you plant it three feet apart. The other thornless varieties grow like the trailing types popular on the West Coast. The plant maintains a compact crown and does not spread. The new canes can range far. My plants of Hull produce canes 15 feet long with several six-foot side branches. In the second season, flowering laterals arise from all the leaf nodes, top to bottom. The less you prune, the more fruit you get. The most space-efficient way to grow trailing blackberries is in a fan-shape along a wire trellis or espaliered to a wall. The canes are very flexible and can be bent to cover a space completely. To get the most from the plants, let them get as tall as you can comfortably reach. On a six-foot trellis, use five wires, the lowest positioned two feet above the ground, and the rest spaced a foot apart. Let the new canes grow along the ground. Bunch them together directly under the trellis periodically to keep them out of the way. Where cold damage is no danger, you can tie them up to the trellis as soon as you prune away the old canes after fruiting. (This seasonal handling of canes is why Waldo is such a boon.) Where snow cover is dependable, you could leave them on the ground all winter to grow varieties far too tender to survive the winter unprotected. A loose, dry mulch also works. The traditional trellis for trailing berries uses just two wires, one at four and a half feet and the other at six. The canes are laced up and down through these wires. It is fast and keeps all the berries up high high for easy picking. But the space below the bottom wire is nonproductive. The history of all the bramble fruits -- blackberries and raspberries -- is one of constant improvement, so keep alert for even better new varieties in the future. Thornlessness is high on everyone's list of desirable traits, so there will certainly be more of those. Breeders are always looking for better cold- hardiness and disease resistance too. If you know of any especially cold-hardy blackberries, breeders would appreciate hearing about them. And although the phenomenal size of the newest blackberry introductions make it hard to believe, fruit size and yields are likely to go still higher. The new Arkansas varieties have berries twice as big and yield five times more than varieties developed prior to 1970, and their originator, Moore predicts even more prolific plants. When you look at the history of fruit breeding, blackberries have recieved the least attention of any crop we grow. Our work is really still in its early stages. The yields can go even higher, and the fruit can get bigger. My biggest fruit are 11 grams now, and I expect we'll get to 16 grams in the near future. That's fruit the size of small plums. And there are a lot of interesting flavors we will be able to work into them. We've come a long way with blackberries in a very short time, but in many respects our improvements have just begun. Jack Ruttle is senior editor at National Gardening
Provided by NGA Reprinted with permission HouseNet, Inc.
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