Blackberries

Growing Blackberries in the Owens Valley

by Alison Collin, Inyo-Mono Master Gardener Volunteer

Blackberries and their hybrids have similar requirements and growth patterns.

Requirements: Partial sun, shaded from strongest afternoon rays either from dappled shade produced by a high canopy tree, or artificial shade cloth. Slightly acid soil with pH around 6 -6.5. Good organic matter content in soil with surface mulch. Cool roots with moist, but not wet, soil. Regular irrigation; 1”-2” of water per week during growing season - they should not dry out. These are more vigorous than raspberries with much longer canes so need a support system of wires attached to sturdy posts in order to keep them tidy. This year I found that a plant which had been attached to an east-facing solid, wooden fence had problems with reflected heat.

Fertilizing: If you use manure or compost, apply it in the late fall or early winter to allow leaching of excess salts by rain. Blackberries require at least yearly applications of a nitrogen-containing fertilizer for good growth and fruit production. Fertilize blackberry bushes in the early spring just as they begin to put forth new growth. Use 1 pound of 20-20-20 granular fertilizer for every 25 feet of row, broadcasting it evenly around the base of your shrubs. If you use 10-10-10 fertilizer, apply 2 pounds for every 25 feet of row.

Basic types and growth habit: Varieties may be thorny (and they are very thorny) or thornless; erect or trailing. They have a 2 year cycle, growing vegetatively one year, and producing fruit on those stems the second year, after which those stems die. Some have now been bred to produce fruit on the first year canes (these often have the word “Prime” in their name) but these perform poorly where summers are hot, so will not be covered here.

Varieties: The original wild blackberries tend to be sweeter and less acidic than the thornless erect varieties, some of which don’t become sweet enough to eat out of hand until they are almost too soft to pick, but do make excellent jams and jellies, requiring no added pectin.

In Bishop the following thornless varieties have proved to be both winter hardy and tolerant of summer heat, although most growers had some issues with fruit shriveling in the exceptionally hot summer of 2017.

The following varieties have proved reliable over several seasons in the Bishop area:

Triple Crown - thornless, vigorous, excellent flavor, ripens August.
Chester – semi erect, cold tolerant, firm berries, mild flavor and is a heavy, late cropper.
Navaho – thornless, erect variety, large crops, sweet berries.
Arapaho – very early, thornless, erect.
Marionberry – Variety “Black Pearl” is thornless and has an excellent flavor, good yields.
Loganberries - These are a hybrid between a blackberry and a raspberry, look rather like a very dark, elongated raspberry with a sharper taste (which has not deterred my small grandson from eating them fresh). They are the first to fruit (June). The roots are not as spreading as raspberries. Produce a few long trailing canes. Floricane bearers only. The bonus is that thornless varieties are readily available, and once the canes have been tied to a support all one has to do is wait for the crop.
Boysenberries - Large, elongated sweet/tart purple fruit of excellent flavor. Trailing habit, thornless varieties available.

Planting and Pruning: Planting is best done in early spring in cold winter areas. For semi-erect cultivars, space plants 5 to 6 feet apart. Space erect cultivars 3 feet apart. Space trailing varieties 5 to 8 feet apart. Space rows about 8 feet apart. Buy plants from a reputable source since they can be infected viruses in home gardens, especially if growing near wild blackberries. Healthy stock may be propagated by tip rooted cuttings – the tip of a new stem is allowed to touch the ground and is buried under an inch or so of soil where it will then root and form a new plant, and can be detached from the mother plant in spring.

Plant shallowly: about one inch deeper than they were grown in the nursery in good moisture-retentive soil containing a generous amount of organic matter. Mulch well with organic matter.

Pruning basically consists of removing the two-year-old canes that have borne fruit and tying the new current-season canes to supports. These can be identified by darker, older-looking stems which have the remains of fruiting laterals evident.

Unfortunately one of the features of blackberries and their relatives is that the new canes grow vigorously and can attain quite a size before the older canes have been harvested, so it is important to prevent damage to the new growth from trampling. Erect and semi- erect varieties can be tied in to the wires as they grow, but in colder areas the new trailing primocanes are often laid out in bundles along the rows where they can be protected from frosts if necessary, and are then tied up in spring.

Trailing blackberries: After the fruit harvest period, the old fruiting (floricanes) are removed to the ground. However, unless there is a lot of disease, it’s best to delay removing the old fruiting canes until they have died back considerably. This allows the dying canes to move nutrients back into the crown and roots. After old fruiting canes are removed, train the primocanes up on the wires. Work with one or two canes at a time in a spiral around the trellis wires. Canes from adjacent plants may overlap a little. No pruning of primocanes is necessary.

Erect blackberries produce stiff, shorter canes that come from the crown and from root suckering (often forming a hedgerow). These benefit from summer pruning. Remove the top one to two inches of new primocanes when they are four feet tall. This causes the canes to branch, increasing next year’s yields. Plants will require several pruning sessions to tip each cane as it reaches the four foot height. Suckers that grow outside the hedgerow should be regularly removed. In the winter, remove the dead floricanes (old fruiting canes) from the hedgerow. Also shorten the lateral branches to about 1½ to 2½ feet.

If you have semi-erect blackberries, they are easier to manage on a Double T trellis. Install four-foot cross arms at the top of a six-foot post. Install a three-foot cross arm about two feet below the top line. String high-tensile wire down the rows, connecting to the cross arms. Semi-erect berries need to be pruned in the summer. When the primocanes (New growth canes)are five feet tall, remove the top two inches to encourage branching. Several pruning sessions will be required as canes reach the appropriate height. In the winter, remove the dead floricanes (old fruiting canes). Spread the new growth canes along the wires. Canes do not need to be shortened. However, they can be if they are difficult to train.

Harvesting: Can be extended by planting varieties that ripen at different times. Pick ripe fruit at its prime since these berries do not continue to ripen once picked.

Pests and Diseases: From my own experience, and from talking to local gardeners who have grown berries consistently for many years, it seems that those grown in this area suffer surprisingly little from problems. However, these potentially include verticillium wilt, armillaria and phytophthora root rots, cane borers, rust, aphids, and such insects as Raspberry sawfly. For more information and control details: http://www.ipm.ucdavis.edu/PMG/selectnewpest.caneberry.html.

Further blackberry information on the web: