I am a little late in joining in on this subject. I grow several tuberous Pelargoniums, but I have only been doing so for a year so don't have much experience to share. I do have a question though. I have P. grossularoides from seed. Is it tuberous? It has bloomed all summer - its first - with intensely magenta tiny blossoms. It is the only one I have been able to raise from seed. All of my others came from Arid Lands Greenhouses. Best wishes, Dell -- Dell Sherk, SE PA US Zone 6. Amaryllids, South Americans, Cyrtanthus, Hardy bulbs, succulents and cactus, gesneriads.