It's hardy to zone 7, however, I have heard it may act like a reseeding annual in lower zones.

I planted it in my garden last year-I'll report back if any new seedlings show up this year.

It does reseed itself here is St. Paul, but the seedlings don't bloom in time. It's a great annual though -- I buy lots every year.!

Mine has never reseeded. I usually wintersow mine, though, and it comes up and blooms ambitiously.

I live in Eden Prairie and mine reseeds prolifically each year. It is one of my favorite plants. It doesn't show itself until late spring until the soil is warm. The first seedlings are quite tiny and hard to distinguish from weeds. As of today I think I can identify the first seedlings.

Mine grows in a hot spot next to an asphalt driveway. It often seeds in the cracks of the pavement. It could be this extra heat that helps the plant do so well for me.

As insurance I always make sure to collect some seed each year. I bend the blossom head into a plastic bag and tap it lightly. This way I get some seed without destroying the plant. Also, if I decide to turn the garden soil in the spring I can always reseed.

Before you give up, get on your knees and search around low spots in the garden and around the base of other plants. Within a week or two you should find something.

Good luck!