I was just wondering if anyone had an explanation. My yellow summer squash plants are lovely, but if the squash themselves get to be longer than 3 inches long, they start to rot. I have been picking them young and eating them, so I haven't been that dissappointed, but everyone else keeps asking me why I am not waiting till they get big!

sounds like a pollination problem. I had the same thing happen, I began to hand pollinate some and leave others (as an experiment) and that fixed the problem.

Try spraying or drenching your plants with a good compost tea every week, or more frequently.

Pollination problem. Squash plants have male and female flowers. The females are the ones that have a tiny squash at the base, and the role of pollinators is to take pollen from male to female flowers. If you don't have bees visiting, you can pick the male flowers and "dab" them in the female flowers to pollinate them. It should work fine. Please let us know.