Published on Wednesday, 30 November -0001 00:00
Most summer-bearing raspberry plants are through producing and a few of the fall-bearing varieties are starting to ripen. In most cases, raspberry plants produced a good crop of fruit over an extended period of time. Now it is time to renovate the patch and prepare for a good crop of easy-to-harvest berries for next year.
Left unchecked, a summer-bearing red raspberry patch can become an unproductive, unattractive thicket in a short time. An overcrowded raspberry planting produces small, poorly flavored, crumbly fruit. In addition, the decreased sunlight and air circulation that results from overcrowding increases the likelihood of fungal disease, including anthracnose and spur blight.
Annual renovation of your summer-bearing raspberry plants will keep them at their productive, healthy best. Although raspberries can be renovated any time from late summer after harvest is finished until late March of the following year, late summer renovation often results in slightly more vigorous canes and larger fruit. If plant hardiness is a concern and canes may be lost to winter damage, March renovation is preferable.
To renovate, simply remove all canes that have already produced fruit and then thin all broken or weak first-year canes. Those canes that have fruited are easy to spot at this stage as they have numerous side branches. These canes will die soon anyway, and removing them to the ground will help prevent disease and give the new canes room to grow. The first year canes, on the other hand, are relatively unbranched. A common recommendation is to leave four to six canes per foot of row or six or seven canes per hill in the hill system, but the actual number of canes left in the row after renovation is unimportant as long as they are sturdy, healthy and have room to grow. Do not cut back the cane tips until the following spring when you can determine die-back and winter damage. Never cut off more than 25 percent of the tip of the cane to avoid lowering the yield.
After thinning the old, weak, and broken canes, check your row width. Raspberry rows should be no wider than 12 inches in order to maximize light penetration and air circulation. Removing canes that grow outside the 12-inch width requires frequent attention, but it results in a healthy, easy-to-harvest patch.
Summer is not a good time to fertilize raspberries and it is wise to wait until early spring to apply nitrogen. Summer, however, is a good time to add mulch to the existing mulch or, if you have not mulched your raspberries, put about six inches of straw, hay, pine needles, compost or other organic material between the rows.
If you wish to harvest two crops per year, fall-bearing cultivars of raspberries, like Heritage, Redwing, Autumn Bliss or Autumn Britten, can be renovated as described for summer-bearing raspberries. However, the canes that produced the fall crop should not be removed as they will produce fruit the following summer. Prune them back in the spring to the last node that produced fruit. To maximize yield from fall-bearing raspberries and to avoid many disease and insect problems, cut all the canes to about two inches from the soil surface in late fall when plants are dormant or in early spring before growth resumes. You will harvest ripe berries only in the fall, but the yield will be greater and the quality of the berries will be better.