Ask Mr. Smarty Plants

We don't want to sound snobbish, but we really wish you hadn't bought your plant at a big box store. The bottom line is we have no idea what your plant is or what its growth habits will be. This plant could be a native of some other country, or grown in another state where they prospered and shipped here, where they won't. They almost undoubtedly are hybridized, which makes it harder still.

Botany.com has a long article on blackberries, from which you might try to figure out if your blackberry has tall, relatively stiff stems, which means it will need a supporting trellis or fence, or trails and roots in the soil, and could very well could be popping up all over your yard. There are many other berries, closely related, in the Rubus family. When we searched our own Native Plant Database on Rubus, we got 61 plant names back, of which 24 had "blackberry" in their common names. Of those 24, not a single one was shown to be either native to Texas or naturally distributed in Texas. In other words, they may not prosper here.

The Lady Bird Johnson Wildflower Center focuses its energies and attentions on plants native to North America, their preservation in their (unhybridized) natural state, and propagation. When you buy a "mystery" plant, you really have no way to predict if it will thrive or even live. At this point, it's probably going to have to be your decision whether to keep it in the pot, or try it in the ground. You could try leaving it in the pot for one more year and see what habits it develops.