Dear Luc, Surprised no one has mentioned Yucca Do Nursery in SE Texas. http://www.yuccado.com/ They have 2 or 3 Polianthes and Manfreda in their current listing, but I suspect they may offer others (too few to list) if you ask. They are a very reliable and exciting nursery and a excellent source. The only help on the Prochnyanthes is seed from the rarepalmseeds.com site as Agave bulliana Good luck. Jim W. -- Dr. James W. Waddick 8871 NW Brostrom Rd. Kansas City Missouri 64152-2711 USA Ph. 816-746-1949 Zone 5 Record low -23F Summer 100F +