we planted 4 last fall. my father in law grew them from seed, so they are 3 years old now. he said he would pinch/clip the new growth fromteh trunk except for that onthe upper limbs. we did the same thing a couple weeks back. you prune it to basically define the shape of the tree, so use your own discretion. never prune more than about 30% of the tree mass as you could kill it. try to get things before they get too large, i get them when they are basically jsut green leaves forming on teh trunk.

on a new transplant... i would remove the majority .... leave one or two.. and see what the top does.. and when you are sure the top is alive... then SNIP the last two off ... maybe in a week or three .... ken

This is my first time growing the tall dahlias. I started the tubers indoors, and they are getting quite big now. My question is regarding pinching them back. As I understand it, you pinch out all side shoots and disbud side buds in order to get larger flowers. This would give you larger flowers but less of them, right? I'd prefer more flowers even if they were a little smaller, so I am wondering, should I let them grow naturally without pinching? Or, are they pinched in the same way as other annuals, to give you more bloom? I've grown the shorter, bedding dahlias but these seemed to take care of themselves, and I am not sure about the tall ones.

Just trim it off all the way around and chop off its head. Don't remove more than one-third of total growth at any one time, then allow the plant to regenerate before trimming again. Pruning is not an exact science with most plants, especially the shrubby ones. Dry the prunings and put them in sachets and toys etc for your cats to enjoy!