If you have any extra plot of land that gets moderate amounts of sunlight during the day, there's no reason why you can't grow blackberries for food. After planting, there is no real cost to upkeep your blackberries, and year after year you'll be able to collect a few pints or quarts of berries right from your own yard. Be certain of the place where you grow your blackberries, however, because the sweet fruits come on thorny stems your blackberries should be out of the way of children and pets.
Purchase blackberry cuttings or transplants in early spring. Dig a hole for each plant twice the size of the pot or root bag it is in. Space upright varieties three feet apart and plant trailing varieties six to eight feet apart to allow room for growth.
Install a trellis for trailing blackberry varieties that will be able to hold the weight of a heavy trailing vine pulling it downward. Typically, two posts are anchored in the ground behind each planting hole, and horizontal wires are run between them halfway up the height of the posts and at the top.
Plant each blackberry plant into a hole an inch deeper than it was in its packaging. Move soil in around the roots and firm it up without packing the soil in. If your soil is very sandy or clay-like, then replace a quarter of the soil with compost and mix it in well.
Water the new plants well to soak the soil thoroughly. Give the new plants up to an inch of water each week either by rainfall or manual watering over the first two to three months as the blackberry plants become established.
Use twist ties or string to attach the first year's growing stems, or canes, to the trellis system you are using. Allow upright canes to form a natural growth habit and bend over unrestrained.
Feed each plant with a half cup of fertilizer a foot out from the base of each planting in the spring. As summer comes, look for berries to begin to form on the existing two year old stems as new canes emerge from the ground as one-year-olds that only produce leaves.
Collect berries in the morning every three to six days when they start to mature until all of the berries have ripened and been picked. Cut away the canes that set fruit this year after all harvesting is complete. Attach the new one-year-old growth to the trellis so it is prepared for the following year.