Raspberries- September 2017 Plant of the Month
Who doesn’t love raspberries? Not only are they sweet and delicious, these nutritional super-fruits are also chock-full of healthful antioxidants, vitamins, minerals, and fiber. Fortunately, they are easy to grow in school or home gardens in most parts of the country. Fall-bearing varieties (see below for more info) are especially well suited for school gardens, as their harvest period occurs when students have returned after the summer break. How many plants to set out? Well, you can never have too many raspberries, but you can expect about 18-20 pints of berries from 10 red raspberry plants once they are established.
- Season of Bearing: If you look in catalogs or go to a garden center, you'll see two different categories of raspberries for sale—summer-bearing and fall-bearing (also called everbearing). To understand the difference, you need to delve into a little berry biology. The new shoots, or canes, that grow each year in the spring from a raspberry plant’s root system are called primocanes. On summer-bearing varieties, these canes grow vegetatively the first year, producing only leaves. Then, in response to the shortening days and cooler temperatures of fall, they develop flower buds that will overwinter. The following summer, the flower buds on these canes, now called floricanes, produce flowers, which in turn produce fruits. After they finish bearing, these two-year-old canes die. Meanwhile, new primocanes sprout in the spring to continue the cycle.
Fall-bearing (or everbearing) varieties of raspberries behave a little differently. Unlike the summer-bearing types, in the fall the first-year primocanes produce flowers and set fruits on the top 10 to 12 buds on the cane. The following summer these same canes, now called floricanes, produce a smaller crop of berries farther down on the cane, after which they die. While you can harvest two crops from fall-bearing varieties, many gardeners cut down all the primocanes after the fall harvest, bypassing next season’s second, smaller summer crop, in order to have the plants produce one larger harvest each autumn.
- Color: Red raspberries are probably most familiar, but there are also yellow, purple, and black varieties to choose from, each with its own distinctive flavor. Try visiting a farmers’ market to sample different colors and varieties of raspberries to help you decide what to plant in your garden.
- Regional Adaptation: Raspberries generally grow best in areas of the country with relatively moderate summer temperatures. If you garden in the warmest parts of the country, such as the Gulf Coast, Southwest, and southern California, look for varieties that have been bred to tolerate heat better. Your local Cooperative Extension Service may be able to suggest varieties that will do well in your climate. Black and purple raspberries are generally less winter cold hardy than red and yellow varieties. If you garden in a northern part of the country, select varieties adapted to your cold hardiness zone.
- Thornless Canes: The canes of most raspberry varieties are covered with spiny prickles. However, some varieties have been bred to have thornless (or nearly thornless) canes. These might be especially well-suited for plantings that will be cared for and harvested by young children.
Site: Prepare a bed for your raspberries that is 2 feet wide and as long as you like. Full sun and well-drained soil are musts. Test your soil and, if necessary, amend to bring the pH level to about 6.0. Work in several inches of compost and a complete organic fertilizer. It's a good idea to avoid planting raspberries in a spot where strawberries or members of the tomato family grew previously to avoid the possibility of transmitting a fungal disease called Verticillium wilt. And, if you can, try to plant at least 600 feet from any wild brambles to reduce the likelihood of disease transmission from the wild plants.
When to Plant: Plant dormant, bare-root plants (this is how plants will come by mail-order) in early spring as soon as you receive them. Container-grown plants can be set out later into the summer months, but spring weather is usually most conducive to the plants’ establishment.
Planting: Space your red raspberry bushes 2 feet apart in the row (black and purple raspberries need a little more room, 30" and 40" respectively). But before you do any planting, you'll need to erect some sort of trellis to support the canes as they grow. This will help to keep the berries clean and make them easier to pick. One common design uses a five foot high, T-shaped support at each end of the row, with the crossbar the width of the row. Lengths of 12-14 gauge wire are strung 4 feet above the ground and 3 feet apart from one crossbar to the other along each side of the bed.
If you are planting dormant, bareroot bushes in spring, soak them in water for a couple of hours to rehydrate the roots before planting. Set plants in the ground so that the crown is just at ground level. Now comes the hard part. Cut the tops of bareroot plants back to the ground; this will remove any diseases that may be present on the canes and helps to get the plants off to a good start. You don't need to cut back container-grown plants.
Raspberries have shallow root systems and will benefit from a mulch to keep weeds down and soil moisture consistent. Placing a soaker or drip irrigation hose under the mulch is a good way to assure your plants get the water they need.
Care: Give your raspberry patch a light feeding with a complete organic fertilizer such as 5-10-10 each spring and a topdressing of compost each fall.
In late winter or early spring, before new growth begins, prune out last year’s dead floricanes by cutting them back to ground level. Their silvery-brown, peeling bark will distinguish these spent canes from the greener, more succulent overwintered primocanes (which will become the current season’s floricanes) that you will leave growing. If the row has filled in and is crowded, thin out these bearing canes, leaving 3 to 5 of the strongest per linear foot. If you notice suckers coming up outside of the bed, dig them out so your patch doesn't turn into a jungle. Finally, tie the bearing canes to your trellis, tying roughly half the canes to the wire on one side of the bed and half to the second wire. This opens up the center of the row to light and air, reducing disease problems, and makes harvesting easier.
Follow the same pruning procedures to harvest two crops from fall-bearing varieties. To harvest only one fall crop, cut back all the canes to ground level in late winter or early spring.
- Raspberries are generally pretty problem-free. But there are a couple of insects that you may need to deal with, chief among them Japanese beetles. These omnivorous pests enjoy a good raspberry leaf, so you may need to control them with handpicking or sprays of neem oil. If you notice the tips of your canes drooping over, the raspberry cane borer is probably at work. Look for rows of punctures about 6 inches from the tip of the cane. This is where the female beetle has laid her eggs. When these hatch, the developing larvae tunnel down through the shoot, causing it to wither. To control this pest, simply cut off and destroy the shoots below where the larvae are active.
- If you see a whitish-gray powder on the leaves, it is probably a fungal disease called powdery mildew. This is often more of a problem in a crowded patch with poor air circulation, so be sure to thin out your raspberry bed each spring.
Harvesting: Raspberry fruits are ready to pick when they separate easily from their core, which stays attached to the plant. Ripe fruits are very perishable, so harvest berries frequently. Pick into shallow containers to avoid crushing fragile berries. Wash berries right before eating since they won’t store well if they are damp.
Fresh-picked raspberries are so delicious, you’ll probably find most of them get eaten as is, straight from the garden! But if you have some extras, try this tasty and easy recipe for Pineapple-Raspberry Parfaits from Eating Well.
- Raspberries are in the same botanical family as roses.
- One cup of raspberries supplies over half the daily value of Vitamin C. Raspberries also supply an abundance of healthful antioxidants.
- Each raspberry fruit contains approximately 100-120 small seeds.
- Black raspberries are native to North America. Red raspberries originated in the Near East. It is thought that Roman soldiers helped to spread the plants throughout Europe.