Look for these fall fruits and vegetables at farmers markets and in produce departments for the best flavor (and greatest value) in season. Specific crops and harvest dates of fall produce will depend, of course, on your region's climate. See these state-specific seasonality guides for more details.
If I remember right Walmart has a 30 day return policy with a receipt. Without a receipt the only thing they will do is exchange it for the exact same thing. If you have the receipt you should be able to get if fixed by the manufacturer, but sometimes they only have a 90 day warranty.
There is no law for or against whether you need a receipt to return an item. That is a policy up to the company. If the company refuses to accept the refund without a receipt, your only other recourse would be to go through the manufacturer for a replacement.