Beginner Gardening: Pinching back seedlings - how do you do it?, 1 by bmblsad

bmblsad wrote:
I started seeds for the first time this year - marigolds, impatiens, zinnias, snapdragons, petunias, sweet william, alyssum, straw flower and pansies. First, it was tough to get just a few seeds in each container, especially the snaps, so multiple plants sprouted in each little container. As they grew, I know I should have thinned them - but they were so tiny and delicate that I couldn't bring myself to do it for fear I would destroy them all. So I let them grow together. I have since transplanted them to interim containers until it's time to move them into their official summer residences (pots and window boxes). When I transplanted I thinned them a bit, and that did help most. But, some are still kinda leggy and weak, in particular the alyssum, tom thumb impatiens, zinnias and sweet william. So, should I pinch them back to try to sturdy them up a bit before putting them in the garden? And if so how do you do it? Just a couple of leaves off the top? the whole top? The pic was taken before I transplanted to interim containers. The alyssum is on the right, pansies and petunias in the middle, pansies to the left, and snaps in the round container in the back left corner.