This is actually one of the best times of year to grow vegetables. Can You Still Plant Vegetables This Late? Our Top 6 Cool-Season Vegetables to Plant NowSpinachToni JardonYou can harvest baby spinach in as little as three weeks. Spinach needs cooler temperatures, so plant in mid- to late summer or early fall, depending on where you live, for fall and early-winter harvests. For a fall harvest, look for quick-growing dwarf varieties that mature in about two months.