Blackberries (Rubus fruticosus) and raspberries (Rubus idaeus and Rubus occidentalis) belong to the same genus, and their close relationship shows in the similarities of their form, growth habit and fruit. Because their cultural requirements are generally compatible, blackberries and raspberries usually can be grown together successfully in a garden.
Raspberry and Blackberry Species
Blackberries and raspberries are members of the rose family (Rosaceae), and they belong to the group of plants commonly referred to as brambles. They produce long, arching stems called canes, and the canes are often thorny. The fruit of blackberry plants is borne on canes that were new the previous growing season -- canes in their second year. Depending on their variety, raspberry plants produce fruit either on their second-year canes or their first-year canes -- those that formed during the current growing season.
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Blackberries are winter-hardy, or perennial, in U.S. Department of Agriculture plant hardiness zones 3 through 9, and raspberries are winter-hardy in USDA zones 4 through 9. Blackberry and raspberry cultivars, however, have been developed to tolerate a wide range of climatic conditions. If you intend to plant blackberries and raspberries together, then choose cultivars with similar temperature tolerances, which their USDA zones indicate.
Blackberries and raspberries can be distinguished from one another by the structure of their fruit. When picked, raspberry fruit pulls away from the central core around which the fruit grows, leaving a hollow space in the center of the berry. Blackberry fruit comes away from its stem with its core intact.
Both raspberry and blackberry plants do best when grown in a location that is exposed to full sun. They thrive in loamy soil that holds moisture well but drains adequately and does not remain saturated with water. Working compost into the planting bed helps to increase the moisture-retention capability of the soil and improve the soil's texture and nutrient content.
Water, Reproduction and Harvest
Raspberries and blackberries require consistent moisture throughout the growing season, but their access to water is especially important while the plants develop fruit. Irrigate the plants' soil as needed to ensure it receives 1 to 2 inches of water per week total from rain and/or irrigation.
Blackberry and raspberry plants reproduce via suckers, which sprout from the plants' bases. Both kinds of plants also take root and develop new plants where the tips of their canes touch the ground. Propagation is simple, either by separating and transplanting suckers or by intentionally burying cane tips to produce new plants.
Blackberry fruit is usually ready for harvest in summer, typically in July in many parts of the United States. Many raspberry cultivars also produce fruit in summer, but ever-bearing types can produce two crops per year, one in spring and one in fall. Planting ever-bearing and summer-bearing cultivars together can provide a berry harvest throughout much of the growing season.
Blackberries tend to be vigorous spreaders, and they're likely to require pruning to control their growth. Prune fruit-bearing canes of both blackberry and raspberry all the way to the ground right after they finish producing fruit. In late winter or early spring, before their new growth begins, prune away all dead canes and canes that were damaged during winter, and remove some canes so that each plant has four or five healthy canes to begin the growing season.
Use sharp pruners, and dip their blades in isopropyl rubbing alcohol before you begin pruning and after each cut to avoid spreading plant diseases and pests.
The precise fertilizer needs of your blackberries and raspberries will depend on the nutritional content of their soil, which you can determine through a soil test from your county's Cooperative Extension Service office or a garden center.
In general, give each first-year plant 1/4 pound of dry, 10-10-10 fertilizer in late spring after planting it. Give each established plant 1/4 to 1/2 pound of dry, 10-10-10 fertilizer in winter or early spring before their new growth begins and again in summer. Scatter the dry fertilizer in an 18-inch circle around the base of each plant, and then water the soil well.
Pests and Diseases
Blackberries and raspberries are vulnerable to fungal diseases such as anthracnose, botrytis, Verticillium wilt and rusts. In the garden, it's often possible to control these diseases by removing some canes to provide good air flow between the remaining canes and plants, avoiding overwatering and keeping the planting area free of weeds. Remove and destroy all infected plants as soon as you see disease symptoms, which include stunted or deformed growth, stem lesions, powdery substances on leaves and leaf drop.
Common insect pests include cane borers, which weaken and kill canes as they feed. Control infestations by cutting canes just below the spots where you see pest damage, and immediately remove and destroy the affected tissue.