Spinach seeds produce a crop that's a valuable source of beta carotene, iron, and vitamin K. The trick to growing great spinach is to use the right varieties in the right season. Spinach is a cool season crop that bolts as the days get long and hot. That’s why it is usually grown in spring and fall — and in the winter on the coast. Some varieties do a little better in summer conditions. Baby-leaf varieties can be grown at almost any time of year, but harvest them promptly or they too, will bolt. Spinach is grouped in the family Amaranthaceae, so it is a cousin of beets, chard, and quinoa.