When to Pick Summer Squash
Summer squash includes any squash that has a thin, tender skin such as:
Zucchini Yellow crookneck Patty pan/Scallop Yellow straightneck
The size of summer squash can become rather large, but you will enjoy them more if you pick them small. The best time to harvest squash of these varieties is while they are still small. The size of summer squash when it is ready to be picked is around 6 inches (15 cm.) long or wide, if it is the patty pan variety. Beyond this size, summer squash begins to develop a think skin and becomes bitter. The flavor is not the best for cooking. Frequent harvesting will also encourage the plant to produce more fruit.
When to Pick Winter Squash
Winter squash includes any squash that you can store through the winter. Popular types are:
Butternut squash Acorn squash Spaghetti squash Buttercup squash Hubbard squash
Winter squash are used when they are fully mature. This means that the best time to harvest squash of this variety is at the very end of the growing season, right around the time of first frost. If by chance your vine is damaged by pests or weather that forces you to harvest early, other indicators of a winter squash that is ready to pick is to tap on it gently. If it feels solid and sounds slightly hollow, than it is ready to be picked.