Blackberries, delicious in jams and pies, can actually be black, dark red or yellow, according to the Oklahoma 4-H. The United States is the world's biggest producer of the fruit, and much of it is grown commercially in Oklahoma. Blackberries also are easy to grow in the home garden.
Plant your blackberry bushes in a sandy, loamy soil that has been amended with organic material. Blackberries need good drainage and should be planted up to 3 feet apart. According to the Oklahoma Cooperative Extension Service, blackberries in this windy state need a slight, north facing slope to prevent spring frost injury and to protect plants from southwest winds in summer.
Mulch your blackberry bushes 4 inches deep with pine bark or wheat straw. According to the OCES, not only will the mulch control weeds, it also will conserve moisture, prevent winter injury to crowns and promote growth of the extensive fibrous blackberry root system. Put down fresh mulch each fall after the first frost. Protect trailing varieties by covering canes on the ground with straw mulch at least 4 inches deep through winter.
Fertilize after the first year when the bushes are blooming. Fertilize a second time immediately after harvest. According to the OCES, use a total of about 10 lbs. (5 lbs. at each application) of a complete fertilizer such as 10-20-10 or 5 pounds of ammonium nitrate per 100 feet of row.
Prune bushes starting in the second year. Do not prune first-year plants or train them to a trellis. After the second year's harvest, trim the last few inches of new canes, leaving them about 3 feet tall, OCES suggests. Also remove old canes near the plant's crown and dispose of them far from the planting area to prevent the spread of disease.
Support trailing blackberries and semi-erect blackberries with a trellis. OCES suggests a trellis shaped like an "F" or a "T," adding lower wires and crossbars to the “T” to make a “V” trellis for easier training.
Water your bushes when the first inch of soil below the mulch is dry or when the plants begin to wilt. The more water the bushes receive, the more juicy the fruit will be. Water deeply, at least 6 inches down. Do not overwater, as it will kill the roots.
Pick your fruit when it turns a deep blue-black color and starts to soften. According to OCES, a “taste test” is the often best indicator of when to pick. Harvest in the morning before the sun heats up the field.