Blackberries are red before ripening.
image by Laurie Reece/sxc.hu
There are two types of blackberry plants: ones that are strong enough to stand on their own or ones that need trellises or posts for support. No matter which kind you have, blackberries are biennial plant that only bear fruit once. Fortunately, blackberries do not need much care, but doing a few things can help your blackberries thrive to their fullest potential.
Prune blackberry plants after harvesting. In their second year, blackberries bear fruit. The first year they only produce leaves. Prune away the plants that produced fruit and any weak or damaged plants. Keep all the other green blackberry plants which will bear fruit next year.
Prune away weeds, grasses and other unwanted plants. This is essential so that the blackberries can use all the possible water and nutrients.
Keep blackberry plants watered. Blackberry plants have deep roots, so water them well enough so that the water soaks in, especially while fruiting. Typically one inch per week from June until the end of the harvest is sufficient. Using mulch, such as sawdust or bark, will help retain moisture. It will also keep the plants warm underground during the winter.
Fertilize blackberry plants in early spring. Use a fertilizer that is labeled 10-20-20 and follow label instructions as each brand of fertilizer has different potencies and release rates. You can also add an additional pound of ammonium nitrate, which is 33 percent nitrogen per 100 feet of plants.