Blackberries produce on two year old canes, after which they die, but the crown is busy making many more canes for you and you have to be diligent to keep them up off the ground, for they will root wherever the growing tips touch the ground. This will quickly make a thick blackberry patch that will be difficult to cultivate and pick from. But this also makes it easy to propagate them to fill in empty spots along your row. You can just poke the tips of a growing new cane into the dirt and step on it. In a few week it will grow roots. Then you can cut it off and plant it wherever you want. In the spring, cut out the old dead canes and dispose of them.
Blackberries are very drought hardy, but the key to large fruit is water. From first bloom until you pick the last berry make sure to water them when needed. Don't over fertilize them. A little each spring and fall is all they need as the roots are very shallow, and too much will easily burn them. Don't water with a sprinkler because this encourages disease; instead use a soaker hose or drip irrigation under a thick mulch. A black hose heats up a lot in the sun and you will be watering your plants with boiling hot water!
Blackberries get some diseases, but most of their problems are viruses for which there is no cure except to destroy the plants and replant in fresh dirt somewhere else. Order from a responsible nursery and keep an eye out for virus symptoms. If you find some with virus dispose of it quickly before it infects the other plants. Be sure to wash your tools in bleach that you used to cut out the diseased plants, for you can spread disease with infected tools. Wild blackberries canes are often hosts of viruses. The one disease that you might watch for is Can and Leaf Rust that responds to a fungicide. Lots of rain encourages disease, but that is usually not a problem here in Central Texas. The climate in Central Texas is actually quite suitable for growing blackberries. They are tolerant of many soil types. They like it best on the neutral side, but they are not really very picky. Using mulch over several years will help even out your soil pH, and help conserve water, especially if you have sandy loam.Blackberry disease pictures and descriptions
Blackberries need aeration, adequate water during production, and good drainage. That's all there is too it except for maintaining your patch by pruning and propagating new canes, and tying up your rows. I don't know why more people don't grow them here in Central Texas. The huge clusters of fat, juicy blackberries the size of the first knuckle on your thumb are much easier to pick standing up, than going out and trying to pick thorny, wild dewberries trailing on the ground amongst all the poison ivy.
Blackberry row at Hummingbird Hill, June 2010