by Fred W. Card, reprinted from the Cyclopedia of American Horticulture, 1902
A name applied to various species of Rubus, of which the receptacle remains with the drupelets when fruit is picked. As a commercial fruit, it is known only in America. Although a well-known wild fruit from the earliest times, the Blackberry has only recently made its appearance among the more orderly and promising garden fruits. The type species is Rubus nigrobaccus, although it has long been known under the name Rubus villosus (see Rubus). It is a most variable species, and the number of forms which may be recognized depends only upon the judgment of the botanist who is reviewing them. There are several distinct types or groups in cultivation. (1) The Long-Cluster Blackberries, Rubus nigrobaccus. The plants grow tall and upright, the leaflets are long-stalked, rather finely serrate and taper pointed. The flower cluster is long, leafless and open, with the individual flowers standing almost at right angles to the central stem. The fruit is normally oblong or thimbleshaped, sweet, rather dull in color, with drupelets small and closely packed. The Taylor is one of the best representative of this class. (2) The White Blackberry, R. nigrobaccus, var. albinus. Similar to the above, but with nearly round, yellowish green canes and pinkish cream- or amber-colored fruit. Many varieties of this type have been introduced, but none have attained prominence. (3) The Short-Cluster Blackberries, R. nigrobaccus, var. sativus. This is the commonest form of cultivated Blackberry, and includes such varieties as the Snyder, Lawton and Agawam. In this type the clusters are shorter, but leafless, the pedicels more oblique, the fruits shorter and rounder, glossy black, the drupelets large and irregularly set. The leaflets are broader, coarsely and unevenly serrate, or jagged and less tapering at the point. (4) The Leafy-Cluster Blackberries, R. argutus. This is a lower and more bushy form, with narrow, coarsely toothed, light-colored leaflets and short cluster, having simple leaves intermingled with the flowers. Its best common representative is the Early Harvest. (5) The Loose- Cluster Blackberries, R. nigrobaccus x villosus. This is a group of hybrid origin, being intermediate between the Blackberry and dewberry (see Dewberry). The plants have a low, spreading habit of growth, broad jagged and notched leaves, short dewberry-like clusters, with large, roundish fruits, made up of very large, loosely set drupelets. The Early Wilson and Wilson Junior are its best known representatives. (6) The Sand Blackberry, R. cuneifolius. A sturdy little shrub, armed with vicious recurved thorns, with thickish, wedge-shaped leaflets, whitened woolly beneath. The clusters are few flowered, opening from the center outward, the fruit roundish, loose-grained, very black and good. Known in cultivation only as the Topsy, or Tree Blackberry. (7) There is still another type of Blackberry, known as the Thornless or Mountain Blackberry (R. Canadensis), but it is not in cultivation. This is characterized by smooth, unarmed canes, narrow, sharp-pointed leaflets, the upper ones borne on long, slender leaf-stalks, an open flower-cluster, a short, roundish, glossy blackfruit, with large drupelets. It ripens later than the common Blackberry, and is not so good in quality. For further account of the Blackberry tribes, see Bailey, Evolution of Our Native Fruits.
The first Blackberry introduced into cultivation was the Dorchester, which was exhibited before the Massachusetts Horticultural Society in 1841. This was followed by the Lawton a few years later, which became much more prominent. The Kittatinny soon divided honors with this, and both now largely have given place to the Snyder, which is undoubtedly the most widely grown variety of the present day. This, like many commercial fruits, is a variety of poor quality, but extremely hardy and productive. The rapid strides made by the Blackberry in cultivation prove that a place was ready and waiting for it in the pomological world, a place which it has proved itself eminently fitted to fill, owing both to its desirable qualities in general and to its ability to rapidly vary and develop new types. At the present time (1902) it is one of the most important, most generally liked and most profitable bush-fruits grown.
The blackberry thrives on almost all soils, but to reach perfection demands a strong loam, retentive of moisture and tending toward clay rather than sand. Soil must be well drained at all times. If too rich in humus and nitrogen, a tendency toward a rank growth of plant, with diminished fruitfulness, appears, while a light, sandy soil will fail to carry the fruit through periods of drought, which is usually the greatest obstacle to success with this fruit. For this reason a cool northern exposure is always desirable, and in the region of the Plains, a good windbreak on the south and west is very beneficial. Fertilizers containing a liberal proportion of potash are most suitable. Too much stable manure, or nitrogen in other forms, will induce a rank growth of canes at the expense of fruit.
Plants are propagated either by root-cuttings, or by means of the suckers which naturally spring up about the parent plants. The latter are most commonly used in commercial work. Root-cuttings may be made in the fall and carried over winter in sand, or started under glass toward spring, or the cuttings can be made in spring and sowed in furrows, like peas. Planting is best done in spring, as a rule. If set in the fall, each plant should be covered with a mulch of earth or strawy manure, which should be removed in spring. The rows should be about 8 feet apart, and the plants may be set from 2 to 4 feet apart in the row. At the latter distance, cultivation may be given in both directions for the first year or two. With high culture, good results may be obtained by planting in hills, 7 or 8 feet apart each way.
Pruning the Blackberry is not difficult, yet upon its proper performance depends much of the success of the crop. The old canes should be removed yearly, preferably in summer, as soon as they have borne their crop of fruit. They then no longer interfere with the symmetrical development of the young canes, and if gathered and burned at once, much is gained in keeping the field clear of certain fungi and insects. The young canes should be slipped off when they reach a height of 18 inches or 2 feet, in order to induce early branching and a stocky bush with well developed laterals, capable of producing and holding up a heavy crop of fruit. It is very important that the shoots be not allowed to get higher than 2 feet before this clipping is done. They will then elongate and make the bush high enough. If neglected, and later cut back to 2 feet, the buds will be weak, the growth poor, the bush low, and the crop small. The laterals are usually cut back to about 18 inches in length the following spring, but varieties differ in their habit of bearing fruit-buds, and it is not safe to cut by measure. It should be remembered that this spring pruning is the method of thinning the Blackberry, and judgment must always enter into the question of thinning fruit. In the region of the Plains, where moisture is likely to be deficient, both in soil and atmosphere, it is frequently found better not to cut back the growing shoots in summer, but to let them develop one straight cane, which is cut back to 2 ½ or 3 feet in spring. This will generally develop all the fruit which the plant can carry to maturity under such conditions. A few growers in other parts of the country train to wires, and in that case the shoots are also allowed to grow at will, but are left much longer in spring and tied to the wires for support. Close-pruned, stocky bushes may be covered with straw as a protection against late spring frosts.
The best of cultivation is always demanded. In a crop in which so much depends upon an abundant supply of moisture in the soil, none should be allowed to go to waste. Hence, the cultivation should be frequent and constant, but always shallow, for deep cultivation disturbs the roots and induces increased suckering. In small garden patches mulching may be substituted. Growers in the middle West have found mulching with green clover in the row, and cultivating between, very beneficial. In many parts of the country winter protection is absolutely essential to success, and often adds greatly to the yield in other regions, where not considered a necessity. This protection is by no means always called for by reason of extreme cold. The winters of Nebraska and Kansas are nearly always milder than those of central New York; yet during one of the mildest of these, when the mercury reached zero but once, and was then only five degrees below. Taylor Blackberries were killed to the ground, while the succeeding winter, which was decidedly colder, they came through unharmed. It may be as much a matter of moisture as of temperature. The needed protection is best given by loosening the earth on both sides of the plant, carefully turning it down and covering the tips with soil, laying the next plant upon the roots of this, and so on. In mild climates, covering the tips is sufficient; in especially unfavorable ones the whole plant must be covered. The cost of this need not exceed $5 to $8 an acre.
The fruit of the Blackberry should be left upon the plants as long as possible before picking, for it is not ripe when it first turns black. It should never be exposed to the sun after it is removed from the bushes. The Blackberry generally outyields all the other members of this family, and is usually one of the most profitable to grow when properly managed, provided the climate and other general conditions are favorable.
There are several formidable enemies of the Blackberry, but they are generally easily mastered by the alert and energetic grower. Cutting out the bearing canes as soon as they are through fruiting will circumvent the borer which sometimes works in the canes, and will aid in preventing the spread of anthracnose and leaf rusts. The orange rust must be fought by digging up and burning infected bushes as soon as detected, for there is no cure. But this trouble is seldom serious.