My mom had some dahlias tublers given to her about a month ago. She started them of inside, putting them out in the day and taking them back in at night. They started growing stalks about 10 days ago and now the stalks are about 12" high and thin with only two to four sets of leaves on each one. Today I pinched thier tips but I`m wondering can I cut them back to the soil level? Since they are my mom`s ,I wouldn`t cut them back before checking. It`s still too early to plant them outside because our night are too cold. Advice please.