You can prune it back to just above a branching point and it will grow new.

Are you sure it's not warm enough? As long as it's not freezing.

"Can and should tomatillos be pruned "

Ideally, no. It sounds good in theory but doesn't work in practice. In reality the more you prune it the taller it gets. You'll find many discussions about this question over on the Growing Tomatoes forum here.

But pinching off early blooms isn't "pruning". In most cases the plant would have dropped those blooms anyway since it is already highly stressed. If it is already "long and leggy" then it isn't getting nearly enough light. If you can't plant it out soon and plant it deep then root cuttings off of it to use in the garden instead.

Dave

Agree- And don't make the mistake I did when planting out. Mine were about 1 foot tall and I buried them a few inches deeper than they were in the pot. Then we had 20+ mph winds the next day and the stems snapped right at the ground level. The tomatoes right next to them were fine. Unlike tomatoes, tomatillo stems are hollow in the middle and not woody. I would advise staking them with bamboo from the start.

I always pinch flowers off of my transplants and for a week or so after transplanting. I have a few deep 6 packs and they are flowering like crazy. They won't be planted out for another week or two.

Thanks