Spinach is a cool-weather quick-growing annual related to Beets and Swiss Chard. Spinach has high amounts of carotenoids, Vitamin C, Vitamin K, folic acid, iron, and calcium. It is one of the healthiest salad choices you can make. The Basics Annual Height: 6" to 3' Width: 3" to 15" Types: Savory Spinach. Dark green crinkled leaves. It grows flatter compared to other Spinach. It tends to be more cold-hardy and becomes sweet and crispy after a frost. Flat-Leaf Spinach. Grows more upright and easier to wash. Semi-Savory. A hybrid between the two. Leaves aren't as crinkled or as smooth. Starting Seeds of Spinach Seed Depth: 1/2" deep Seed Spacing: 2" apart, thin seedlings to 4-5" apart. Mature 10-12". Days to Germinate: 1 week at 60 degrees. Days to Harvest: 20-30 days for baby greens. 35-45 days mature leaves. Seed Longevity: 1-3 year