What is Raspberry? Information about Raspberry types, cultivation, growing, care instructions and diseases.
Raspberry; any of a number of species of the genus Rubus, the fruits of which separate freely from the receptacle when ripe. The plants are perennial, but they have a characteristic biennial growth habit. New shoots arise from belowground parts in one season, overwinter, fruit in the following season, and then die. Shoots newly arising during the spring of the fruiting season bear the next season’s crop. The canes are generally erect and prickly. The fruits are not true berries but aggregates composed of a number of drupelets.
Species of raspberries are native to most temperate parts of the world. The modern cultivated raspberry has been developed since the 16th century through the use of spccies native to North America and Europe. Raspberries are now grown in many temperate regions for home use and for market. The berries are prized as dessert fruits and in pies, jellies, and jams.
Types: There are two main classes of cultivated raspberry, distinct both in growth and in fruiting characteristics; the red raspberry, a hybrid between the American species R. strigosus and the European species R. idaeus; and the black raspberry, which is derived from the American species R. occidentalis. The red raspberry produces many slender, upright, generally unbranched shoots and spreads rapidly by means of sucker plants. These sucker plants are dug for the establishment of new plantings. The fruit is borne on shoots that arise from the main cane. The black raspberry produces new shoots from individual crowns and forms no sucker plants. The shoots are heavy and branch freely, the lateral branches arching over until the tips touch the ground. These tips root freely when they come into contact with the soil. Propagation is accomplished by tip layering. The fruit is borne on shoots that arise from the laterals. The more important red raspberry varieties are Latham and Williamette; the leading black raspberry varieties, Bristol and New Logan.
Purple raspberries, hybrids between the black and red sorts, have been grown for many years. The plants are vigorous and productive, and the berries are large but of an unusual appearance and flavor. Yellow- or amber-fruited sorts also are grown. In addition, everbearing types of raspberries, which produce one crop in the fall and a second crop in the following spring on the same cane, have been developed. None of these types has challenged the commercial acceptance of the red or black raspberry, and they are of only local interest.
Cultivation: Raspberries grow best in cool, temperate areas in soils that are fertile, moist, and well drained. They may be grown in solid rows or hedgerows or in individual hills. Plants grown in hedgerows are spaced from 2.5 to 3 feet apart in rows 6 to 10 feet apart. Hill-system plants are spaced from 5 to 6 feet apart in both directions. Planting is best accomplished in the very early spring while the new plants are dormant. To maintain high production fertilizer must be applied annually. Bigger yields of larger berries have been associated with the use of straw or similar mulches.
Pruning is essential to the maintenance of a raspberry planting. The black raspberry requires summer topping, breaking out the top 4 inches of the new shoot when it reaches a height of 24 to 28 inches, to foster lateral development and strong plants. The laterals are shortened to a length of 8 to 10 inches in the following spring before growth starts. The red raspberry should not be summer topped. It is pruned in the spring prior to growth to limit the number of canes, and the remaining canes are shortened sufficiently to support the weight of the crop. Stakes or trellises are employed in some areas to prevent wind damage.
Limited production can be expected in the second harvest season, and full production in the third to fourth season. Red raspberries yield from 3,000 to 3,500 quarts per acre, and black sorts from 4,000 to 4,500 quarts per acre. Depending on the grower’s skill, profitable production should be expected for 10 years or more.
Diseases: The longevity of individual plantings is limited by a number of disease problems. The most serious of these problems are created by a group of virus diseases : leaf curl, mosaic, and streak. These diseases cannot be controlled by spraying or by other conventional methods, but must be avoided by the use of planting stock free from the soil sterilant diuron, by isolation of the stock from other Rubus, and by the immediate destruction of plants showing disease symptoms. Although there are differences in susceptibility between species and varieties, all raspberries appear to be affected. Anthracnose, which causes lesions on the stems, has been a major problem in many areas. It can be controlled by means of liquid-lime sulfur sprays in the early spring, followed by sprays of ferbam or captan. Raspberries are also affected by crown gall and verticillium wilt. These organisms can best be avoided in the selection of the planting site.