Very likely, but even more detrimental would be a cross with another different squash in the same species.A halloween pumpkin zucchini cross for example. Many growers grow several types of squash and make no effort to isolate as they are not saving seeds.

Thanks, I'll just roast them!

This year, curbits were my biggest "weed". got alot of produce scraps from produce dept my Gf works at.What gets me is planting good seed in cool soil will rot the seed, where as composting the buggers tilling in to garden in spring, and giving them no attention they will not only grow but flourish. She insisted we let a few grow. Got a few interesting things that looked like lunch lady gourds.They looked good on the steps though.

I have grown seeds from grocery store squash that grew true. I have a large store of Turban (also called Turk's cap) squash from second year plants grown from grocery store seeds. They have grown true every year.

If it is something you really like, I'd go for it.

I'm willing to try growing the seeds if the pumpkin was good, and/or unique. I'm planning on using my nose to tell if the flesh is edible or not, hope that is a good instinct. There were some small acorns that were very very good this year I saved seed from. The seeds are jumping up and if I cut into one later in the year and it doesn't smell like it's parent - good sweet pumpkin flesh - they will still be pretty enough for decorations.

One year I planted the seeds from a sugar pumpkin I got from the grocery store and it did really well. I had loads of vines and many pumpkins, if they had hybridized with anything I could not tell, they looked perfect and tasted as good as the pumpkin I got the seeds from.

This year I am experimenting with seeds I got from a store-bought acorn squash, good chance of getting some hybrid monster but you never know. I started a few seedlings and they are growing as well as the seeds I had bought directly.

In all honesty, I would think the chances of even open pollinated crops being hybridized is fairly low in this day and age. Small family farms may grow many varieties in close proximity to each other, but when was the last time you really saw one of those that sold to a big name chain grocer?

I'd bet the vast bulk of their produce come from huge factory farms where they're planting fields of one thing by the hundred acre. So even open pollinated, there likely wasn't anything but the same variety for a quarter mile in any given direction.