June, I think you dahlias have an insect problem, which causes curling of the leaves. I would repot the tubers into a larger pot using fresh potting soil and treat the plants with Bonide Systemic House Plant Insect Control according to package directions. Best And Happy Yardening, Nancy.
Dahlias Have Extremely Curled Leaves
Question From: j. jondahl - OREGON
Q: Help. stored dahlia bulbs over winter- planted in pot and all three appeared with extremely curled leaves - other wise look healthy. Same bulbs planted in ground look great -