In Season: Available year round Squash includes a number of popular varieties like acorn, banana, butternut, spaghetti, and zucchini. Squash is usually divided into two categories. Summer squash is picked young and has thin skin and soft flesh. Winter squash is left longer in the field or garden and has a hard skin, suitable for storing over the winter months. Unfortunately, not everyone is as appreciative of squash as Americans. When the colonists first introduced the vegetable to Europeans in the 17th century, it was nicknamed "harrow marrow."