Why aren't my blackberry plants budding yet?

I've had these plants going on 4 years this year. I live in south Texas, and we did get a very rare incident with snow. It's now May, and none of my plants have sprouted, budded, or produced any new growth since they went dormant last winter. They don't appear dead, as some of the leaves that didn't fall off, are still green, and the branches seem very much bendable/limber like they're not dead...not a woody bark feeling anyways. They've been watered, but not too much, since I know how to water them properly, and pruned correctly once the growing season last year was over...the fruiting stems. I just know that they should be budding and growing a lot by now, just like my other garden plants, and there's nothing. I've searched everywhere for answers, and just can't find anything. Someone please help.