   Growing Blackberries - December 27, 2006 Jeff Schalau, County Director, Associate Agent, Agriculture & Natural Resources Arizona Cooperative Extension, Yavapai County Blackberries are fairly easy to grow and very rewarding at harvest time. Your level of success will be dependent on good site selection, soil type, and cultural practices which include fertilization, irrigation, and pruning. The payoff is a four-week harvest period of delicious fruit that can be eaten during the growing season or easily frozen for later enjoyment. The blackberry belongs to a group of small-fruit crops called brambles. Brambles have perennial root systems and biennial canes. Canes produced during the first growing season (primocanes) produce fruit the following summer. The canes then die back to ground level during the winter. Blackberry canes are generally prickly with small to large thorns, although some thornless cultivars have been cultivated for many years. Himalaya berries are non-native blackberries with stout, ribbed canes. While the berries are edible, these plants are highly invasive and undesirable for cultivation. Blackberries grow best in sandy loam soil. Otherwise, they can be grown in soils that are at least one foot deep, have good drainage, and have a pH between 4.5 and 7.5. On soils with a pH of 8.0 or above, plants may experience zinc or iron deficiency and applications of zinc sulfate or iron chelate may be necessary. If soil drainage is inadequate, grow blackberries in a raised bed. They perform best in full sun when grown at elevations above 2,500 ft. Blossoms may be damaged at temperatures below 26 degree F and drying winds can damage canes between 20 and 24 degrees F. For this reason, a wind-protected location on a slight slope (non-cold air trapping) will make the best site where wind and temperature are concerns. Blackberries are described as erect, semi-erect, or trailing and thorned or thornless. Erect varieties tend to have square stems and trailing varieties have rounder stems. The University of Arkansas has developed several erect varieties having Native American tribal names. Of these, Navaho and Choctaw should perform well in north central Arizona. Brazos and Roseborough are other erect varieties that should also do well here. Black Satin is a semi-erect variety and Olallie is an excellent trailing variety. New blackberry plants should be purchased from a reputable nursery to ensure they are free of nematodes and disease. Plant vines between February and April. Do not allow the roots to dry out before planting. Cut plant tops back to 6 inches before planting and any broken or damaged roots should also be pruned back. Spacing between individual vines within a row should be 2 to 3 feet for erect varieties and 4 to 6 feet apart for trailing varieties. Rows should be spaced at least 6 to 8 feet apart. Both erect and trailing blackberries should be trained to a trellis. Trellises for trailing varieties are constructed by stretching two wires (3 and 5 feet above ground level) between steel or rot-resistant wooden posts. Erect varieties may be adequately stake with one wire 3 feet above the soil. End posts will need to be strong and well anchored. Proper pruning is essential for good production. Erect varieties should be topped at 3 feet during the first summer. This encourages lateral branching, which is where the fruit will be produced the following year. These laterals should be pruned to 12 inches the following spring. Erect varieties should be thinned to 5 or 6 strong canes per foot of row in the spring. Trailing varieties should be thinned to 6 to 12 strong canes per foot of row and trained to the trellis wires in spring. For both trailing and erect varieties, old canes that have produced fruit the previous year should always be removed. Nitrogen and phosphorus fertilization are the most critical nutrients for blackberry production. Nitrogen should be applied ¼ to ½ lb N per 1,000 sq. ft each spring (at least 6 weeks after planting the first year). Phosphorus can be banded near the root zone at a rate of 1-2 lbs of P2O5 per 1,000 sq. ft. Zinc or iron deficiency may occur and should be treated if symptoms appear. Weekly irrigation should be applied by flood, furrow, drip, or other method that wets the soil to a depth of 1 foot. Sandy soils may require more frequent irrigation. Avoid aerial sprinklers that wet foliage as this could promote disease. Have fun growing and enjoying your blackberries! The University of Arizona Cooperative Extension has publications and information on gardening and pest control. If you have other gardening questions, call the Master Gardener line in the Cottonwood office at 646-9113 ext. 14 or E-mail us at cottonwoodmg@yahoo.com and be sure to include your address and phone number. Find past Backyard Gardener columns or submit column ideas at the Backyard Gardener web site: http://cals.arizona.edu/yavapai/anr/hort/byg/. |