Answer: I think growing dahlias in Dallas could be a little iffy. They can't take the heat and the dry summer air. You might try sending just one tuber to your cousin and suggest she plant it in an area with a few hours of morning sunshine but shade during the afternoon. If she's successful with the one plant, then you can share the rest of the dahlias in your collection.
Best wishes with your dahlias!
Q&A Library Searching Tips