No, it's not necessary. They branch very well on their own, and their stems are wiry, not at all like the more formal, old fashioned zinnias. I use them a lot for their ease of care, and if they required pinching, I probably wouldn't use them. LOL.

I've never pinched mine either. They looked like bouquets in the ground. Flowers all the time.

Enjoy!

Kat

I don't pinch them either, BUT if you put them into good soil and good conditions, you may want to cut them back hard (1/3) in mid summer to keep them from flopping out of the center by early fall. This is probably not necessary up north, but my zinnia season goes from April to November, and they definitely need one cut back.

Donna, I have had that happen, where they flop and the center opens up some, but I thought it might have been because of all the rain we had at the time. I'll keep that cutting back in mind!

Kat

There you go. Not climate, just the nature of the plant. Multiple observations go a long way, don't they?