Only when they flower...say every 20-100 years. There are always some bamboo in flower, but it's not like being able to buy a specific kind of tomato seed for your garden whenever you want. If you can get your hands on some seeds, viability is an issue becasue they lose potency quickly, and, if you do get seedlings, allow about 5+ years for them to get to a modest size. It's also illegal to import bamboo seeds into the U.S. without a special permit and a quarantine, so you have to be satisfied with what you can find here.

All of this is to say that you can buy bamboo seeds, but if you're serious about growing bamboo, it's much more expedient to buy a division of whatever species you want.

thanks