The selection of planting stock is of major importance. Good quality planting stock is the key to success in the bramble fruit enterprise. The disadvantages of poor stock can never be overcome. Many serious production problems are often directly associated with the plants used in establishing the planting.
It is necessary to secure stock from a reputable source to be sure of getting disease-free, true-to-name plants. To secure plants of the desired cultivar, place orders as early as possible. When placing the order, indicate the desired delivery date. One-year-old plants are best.
The state certificate of nursery inspection is the grower's assurance that the plants are as free of disease and insect pests as possible. It is unwise to use plants that do not carry this certificate. Generally, the better the planting stock, the longer lived and more profitable the planting.
Bramble plants, "certified" as having been grown from plants known to be free of virus by indexing and under special conditions to limit virus infestation, have become available through a number of nurseries. The superior growth and productivity of such plants have been well established. Every effort should be made, particularly by commercial growers, to obtain this kind of stock for establishing new plantings. It must be remembered that this superior grade of planting stock is only free of virus and not immune to it. Therefore, the grower must use every precaution to avoid the possibility of the reintroduction of viruses once the new plantings are established.
Nursery stock is available as transplants, suckers, tips, root cuttings, or tissue-cultured plants. Transplants are larger and more vigorous than suckers. Nurseries develop transplants by replanting suckers (red raspberries) or tips (black raspberries and blackberries) and allowing them to grow another year. Transplants usually cost more than suckers. The extra cost charged for these year-old plants is usually not worthwhile for commercial growers.
Dormant suckers are the traditional red raspberry transplant. Black raspberries rarely produce suckers. Purple raspberry suckers are sometimes used but, like black raspberries, they are most commonly propagated by rooting primocane tips, i.e., by tip-layering, during late summer and fall.
To be good quality transplants, red raspberry suckers should retain a portion of the parent plant root, so they may have an inverted "T" or an "L" shape. Transplants with relatively large root systems are acceptable, but those with few or no roots and no part of the parent root are less likely to survive.
Succulent red raspberry suckers (primocanes) may be transplanted in early spring when suckers are five to eight inches tall; however, care must be taken to provide adequate moisture and weed control.
Black and purple raspberries and some blackberry cultivars are propagated by "tip-layering." This is usually done in late August by burying the tips of the current season's cane two to four inches in the soil. The buried tips develop roots and form new plants before dormancy the same year. Before digging, they are cut from the original plant. About six inches of old cane (called the "handle") is left attached to the rooted tip. Plants are shipped with these handles attached.
Rooting cuttings can be used either to produce red raspberry and some blackberry cultivar transplants or to directly establish plantations for fruit production. Roots of variable lengths and 1/16 to 3/16 inch in diameter should be placed at about a three-inch depth in the soil with approximately two ounces of roots per hill, or per three feet of hedgerow.
In vitro "tip cultured," or so-called "tissue cultured," red, purple, and black raspberry plants are available from certain nurseries. When derived from virus-free parent plants and rooted in sterile potting media, this kind of transplant should be free of most serious disease, insects, and nematodes. Tip-cultured transplants may be acquired in several forms:
The second of these forms may be the best choice because cubes can be planted directly in the field after spring frost danger has passed. Using rooting cubes avoids insect, fungus, or nematode contaminations, which can occur even on fumigated nursery land. However, the third kind may reach maturity sooner, and the larger root system may allow survival under drier soil conditions during the planting year.
Dormant plants are best for planting. Plants dug and held dormant in storage, if properly handled, are as good as freshly dug ones. In some cases, they may be superior to freshly dug ones. It is important to keep plants from drying out.
As soon as the dormant plants arrive, open the packages and, if necessary, moisten the roots. Unless planting can be done within a few days, place the plants in storage at about 35°F, or heel them in until they can be planted. To do this, dig a shallow trench, deep enough to accommodate the root systems, in a sheltered area where the soil is well drained. Open the bundles and place a single layer of plants against one side of the trench so that the root systems are completely below the soil surface. Cover the roots with soil and firm carefully. Plants so treated can be held safely for a reasonable length of time (one to two weeks) if they are not allowed to dry out. Do not delay setting plants any longer than absolutely necessary.
When any freshly dug or tissue-cultured plant is shipped with living or growing tissues, it requires a "hardening" process before being put into the field. Set plants outdoors in soil if necessary and place them in a shaded area for two to three days and move to full sun gradually over a five- to seven-day period. Maintain moisture with frequent or daily watering and protect from any hard freezes (28°F or lower).
Although bramble fruits can be propagated rather easily, most growers find it wiser, unless they are keen observers of disease problems, to purchase nursery stock rather than use their own or their neighbor's plants.