Blackberries and Raspberries
Three main types of raspberries are grown in the United States: red, purple and black. They differ in ways other than fruit color. Red raspberries have erect canes and are propagated by suckers. These are usually grown in the Western States. Black raspberries have arched canes that root at the tips. Purple raspberries are hybrids of red and black varieties. The black and purple varieties are grown in the Eastern States.
Varieties of blackberries include boysenberries, ollalieberries, loganberries, and youngberries. Boysenberries are reddish black with an aroma and flavor similar to raspberries. Ollalieberries are slightly longer and more slender than the boysenberry and are a cross between black, logan and youngberries.
Raspberries grow best in cool climates. A wide range of soil types are suitable for growing raspberries, from sandy loam to clay. The most important requirement for the berries is that the soil be deep so that the roots are not restricted. Raspberries should not be planted in an area following the cultivation of tomatoes, eggplant or potatoes. Diseases that affect these plants may remain in the soil and damage the berries. Plants may be set in hills or in rows. Red raspberry plants should be set 2' to 3' apart if planted in rows. Before planting, cut the tops of the plants back to six inches. Set the plants into the hole so they are 2–3" deeper than they were in the nursery. Water after transplanting.
Blackberries do best in deep well-drained soils such as sandy loams and loamy sands. They should be planted in January or February but definitely by April 1. Planting them on raised beds is not recommended; they will easily dry out if this is done. Space the plants 3.5' apart in rows. Space the rows 8' apart. The biggest problem growers have is placing the plants too deep; plant the berries at the same depth they were growing before transplanting. Water after transplanting.
To get maximum yields from raspberries, apply fertilizer every year in the early spring just as new growth begins. Manure works well as does a commercial 5-10-5 fertilizer. Apply this as a top dressing at the rate of 500–600 lbs/acre or spread in a wide band no closer than about 6" from the crown around each hill.
Blackberries require only nitrogen as fertilizer; 200 lbs of actual nitrogen per year is required per acre. This works out to 50 lbs before growth starts, 15–20 lbs about every third irrigation, and 50 lbs after pruning.
BUILDING A TRELLIS
Some red raspberry varieties have long, slender canes that must be tied. They can be staked or tied to a trellis. Set the trellis posts 15–30' apart and run wires between them. Most red raspberry varieties are stout caned and can be planted in hills without training them to stakes.
To build a trellis for boysenberries, use 4" by 5" or larger timbers for the end posts (2" by 2" posts with braces works as well). Use 2" by 2" grape stakes in between the posts at 20' foot intervals, 6' long with 18" in the ground. For ollalies build a 4.5' trellis and run the first wire 1.5' from the ground, the second wire one foot above the first, and so on.
THINNING AND PRUNING
Raspberry canes are biennial; they grow the first year, fruit the second, then die. Only the crown and the roots are perennial. Old canes should be removed as soon as the fruit is harvested. New canes grow from buds on the base of the old canes. Two new shoots usually come up each year. In addition, suckers grow directly from the roots of red raspberries. The new canes and suckers should be thinned immediately after harvest.
Blackberries should be pruned as soon as the harvest is completed. All wood that has produced the current crop should be removed. The berries should be trellised immediately after pruning. Put up only the larger canes and prune the small ones. Generally, no more than 9 canes should be put up on the trellis. A fan-like arrangement is the best way to trellis the vines. The fruiting wood (canes about 6–8' long) is well spread out over the wire, put them over the top wire, wrap them around the middle wire, and then remove the tip. In coastal areas where canes are 10–12' long, they are taken over and under the top and middle wires three or four times; this is referred to as the barrel roll. Tipping, removing the end of the canes, forces out the laterals on which fruits will be borne the following season. A cane that is not tipped will continue growing. The farther berries are from the crown of the plant, the smaller they will be. Winter pruning is done around Thanksgiving; prune to remove all laterals below the lower wire and head back the long laterals at the top of the trellis to 12–15".
By Nancy Garrison, former Horticultural Advisor, Santa Clara County