University of Vermont Extension 
Department of Plant and Soil Science

Spring News Article

Dr. Leonard Perry, Extension Professor
University of Vermont 
Raspberries and blackberries are the two most common bramble fruits—those shrubs with edible berries, and generally with thorns.  Although fairly easy to grow, there are a few cultural tips and pruning techniques which will help you to harvest not only a crop of fruit, but a bountiful one of beautiful berries.
If you’re just planting a berry patch, make sure to choose cultivars (cultivated varieties) hardy and suited to your area.  This is especially true if buying online from distant nurseries, or you live in a colder part of the north.  Many cultivars of red, and fall-bearing yellow, raspberries are hardy through most of the north country.  Be aware that red raspberries generally bear one crop in mid-summer, but some that are often called fall or everbearing have two crops—one in summer and one in fall.  This is important in how they are cared for.
Black and purple raspberries are generally less hardy, so look for hardier selections such as ‘Bristol’ or ‘Jewel’ black raspberry, and ‘Brandywine’ or ‘Royalty’ purple raspberry. Upright blackberries are generally the hardiest types, with the trailing and thornless ones generally less hardy.  Some of the hardiest to USDA zone 5 (-10 to -20 degrees F average minimum in winter) include ‘Darrow’, ‘Illini’, and ‘Kiowa’. ‘Chester’ and ‘Triple Crown’ are somewhat hardy, semi-upright or trailing types.
Once you’ve chosen and obtained your brambles, plant in a well-drained soil in full sun.  As they like to spread, allow plenty of space and don’t plant near flower or vegetable beds.  Best is an area where you can keep rows mowed.  Amend the soil with plenty of compost prior to planting. If you’re planting bare-root plants, cut tops back to a couple inches above the ground after planting.  If planting rooted plants in pots, don’t cut back. 
Space plants 2-feet apart in rows (farther apart for trailing blackberries).  Rows should be about 6-feet apart for raspberries, and perhaps 10-feet apart for blackberries.  Often trailing blackberries need cross pollination between cultivars in order to fruit (so buy more than one), but most brambles are self-fertile and will produce fruit just with the aid of bees (so you can have just one cultivar).
Water well for the first few weeks, if little rain, until plants are established.  If you have fertile soil you may only need compost at planting.  Testing the soil with kits from your local Extension office will yield results on how much fertilizer and lime, if any, to add.  Otherwise, use about 2 to 3 pounds of a low analysis, organic fertilizer such as 5-3-4 per 100 linear feet of row or a liquid fertilizer of your choice.  Apply this again about a month after planting.  Mulch with an organic material such as wood chips, straw, or shredded bark.
In spring of the second year for raspberries, cut back to a couple inches high all plants that didn’t grow vigorously the first year.  This encourages maximum cane growth for a big crop the following year. Add to the mulch, and apply fertilizer as in year one.  Fertilize two-crop cultivars again in mid-summer.  Then, in fall of year two, cut tops of plants back so canes are about 4 feet tall. This makes a stiff plant that doesn’t fall over in winter’s snow and wind. Install a fence or other support if you didn’t already. This can be as simple as two strands of smooth wire on each side of the row between stakes, to keep future canes from falling over.
In spring of future years, add fertilizer and mulch, as last year, to your raspberries.  Trim out any broken canes. Spray with a fungicide according to label directions if you spot any evidence of spur blight, and reapply if needed in early summer.  If young beautiful leaves in spring suddenly turn yellow, and the canes die, this is likely spur blight. 
During summer, keep plants watered if insufficient rain during the 3 to 4 weeks prior to harvest.  Remove any wilted tips which are likely from the cane borer, a common pest.  Cut off just below the two circles you see on the cane near the tip where you’ll often find the larvae inside, living and dining.  
Another common pest on this and other members of the rose family in summer is the Japanese beetle.  Simply knock off into a pail of soapy water.  If using traps for them, place far away from your berry bushes.  The traps have powerful attractants, and beetles will feed on your plants before getting to the traps.  Milky spore is useful on the beetle grubs only in warm climates.
A recent pest causing great concern on soft fruits, including brambles, is the spotted wing drosophila.  Late season fruits appear more vulnerable than those in summer.  Like a fruit fly, this vinegar fly is so named as it is attracted to vinegar.  So one control, and means for monitoring for this pest, is to hang plastic cups among your plants with apple cider vinegar.  Use 32-ounce cups with several holes in the sides, and cover on top.  Use a couple drops of dish detergent, which helps flies sink into the vinegar.
The spotted wing drosophila first arrived on the west coast in 2008 from Asia, and has rapidly spread east and into the northeast, thanks mainly to human transport of infected fruit and plants.  The flies lay eggs in ripening fruit, which hatch into larvae in the ripe fruit.  So one way to prevent this pest is to cover bushes before fruits ripen with a very fine mesh netting or fabric row cover, as used on vegetable crops.  Anchor well to the ground.  Pick fruit right as they ripen, and remove any old or dropped fruit.  Look for organic sprays containing either spinosad, pyrethrin, or azadiractin (from the neem tree), and apply as appropriate and as listed on the label.
In fall, cut one-crop raspberries to ground level and remove all the canes (“floricanes”) that bore fruit that season. These tend to be more woody and brittle, and lighter in color.  Cut out all weak canes, and thin remaining first-year canes (those that did not fruit, the “primocanes”) to 6 inches apart.  These will be the canes that bear fruit the following season.  Cut back remaining canes to 4 to 5 feet high. If you’re growing two-crop cultivars just for their fall crops, you can cut all their canes back in late fall to a couple inches high, as they’ll bear fruit on canes produced the following summer.
With the right care, you should get at least 10 years of harvests from your berry patch, often more, with first harvests the second year.  Figure on one to two pints per mature plant, depending on cultivar and culture.  For 4 people, depending on preference and uses, a guideline might be to plant 8 blackberry plants, 40 red raspberries, and 10 yellow or fall-crop raspberries.  With such a patch you should have plenty for freezing (easy) and jams, in addition to fresh eating. If for fresh eating, choose several cultivars that ripen at different times.  If for processing, you might choose ones that ripen at the same time for ease of handling.
More details on culture of these and less common brambles such as dewberries, loganberries, and boysenberries, can be found in The Fruit Gardener’s Bible, by Lewis Hill and Leonard Perry.

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