Alberto: Thanks for great information on dahlias. We root all of our dahlias, including D. imperialis from stem cuttings and have great success. These can either be stuck horizontally or vertically. On large stem species like D. imperalis, horizontally works much better. Tony Avent Plant Delights Nursery @ Juniper Level Botanic Garden 9241 Sauls Road Raleigh, NC 27603 USA Minimum Winter Temps 0-5 F Maximum Summer Temps 95-105F USDA Hardiness Zone 7b email tony@plantdelights.com website http://www.plantdel.com/ phone 919 772-4794 fax 919 772-4752 "I consider every plant hardy until I have killed it myself...at least three times" - Avent