Yes, deadhead them when the last of the flowers on the stalk bloom out and they should put out fairly continuous new blooming stalks until the first real frost. They won't self-clean and without deadheading they tend to just sit there producing big seed pods. It's not likely they'll self-seed and return in the spring in your zone. Occasionally things happen, even here in zone 4, I'll get random cosmos and petunias, but I don't count on it with any of the annuals aside from alyssum and pansies which do tend to come back for me.

Thank you for the information . . . I'll be curious to see what will happen here with the snaps as far as reseeding, but I will definitely deadhead now that I know. Here in my yard I just cannot believe the amount of cosmos, balsam, feverfew, and cleome as well as alyssym, portulaca and pansies that come up by themselves every year. I can't even weed too early because there are so many little sprouts! Donna

If you don't cut the bloom stalks when they are about half "bloomed out" they will not bloom well all summer at all. Snaps are great to use as cut flowers.
If you cut them they will put on a great bloom until frost....and about 1/3 of the time will live over the winter. Snaps really are a tender perennial. In my zone I have it happen fairly often......and a heavy covering of leaves after frost makes it more likely they will live. They also self seed very well. They won't come true from seed, but they will be lots of plants.
Just remember to dead head the whole stalk before the last of the flowers have faded and you will have continuous bloom.
Linda C

When I grew snapdragons, I did as Linda did...cut the whole stalk (just below the lowest old bloom) when done, not just deadhead the flowers. The ones I had then branched out so I had more blooms. I had the mid size ones, about 12" to 15". Sometimes when you cut the stalk you may see new buds at the top, but don't let that stop you. You'll get plenty more and neater looking plants when you cut the stalk.
Good luck and enjoy!

Kat

You cut the whole stalk below the blooms? Thanks for the info, I'd have never thought to do that. I've never done snapdragons before this year. This is actually the first year I've ever done "real" flower beds. I've never done anything more than a small strip in front of an apartment in the city, but I just moved to the country with all kinds of room to plant and I'm having a ball! I'm full of questions!

That's a great idea, I didn't think of that. I wonder if it would work for lobelia, but I doubt it. It had to be staked, it was worth it.