How to keep your jack-o’-lantern from rotting before Halloween

For many Americans, pumpkins mean that fall is here. In anticipation, coffee shops, restaurants, and grocery stores start their pumpkin flavor promotions in late August, a month before autumn officially begins. And shoppers start buying fresh decorative winter produce, such as pumpkins and turban squash, in the hot, sultry days of late summer. But these fruits—yes, botanically, pumpkins and squash are fruits—don’t last forever. And they may not even make it to Halloween if you buy and...