Spinach is one of the few vegetables with beets and chard that prefers a neutral to alkaline soil (pH 7.0 or above). If your garden soil is sandy and acid, be sure to get a lime recommendation based on a soil test before planting spinach. Spinach is also a heavy feeder.
Spinach thrives in cool weather and short days so it’s best to grow it in the Autumn and Spring for most gardeners. Northern gardeners can plant an early spring crop followed by another in midsummer to mature before the first hard freeze. In southern gardens spinach easily tolerates a light frost, especially if it is acclimated. In case of a sudden or hard freeze, cover with a fleece to prevent frost damage.
Plant spinach seeds an inch apart in rows 14-18 inches apart and cover the seeds with a 1/2 inch of soil. Keep the soil moist and after the seeds germinate thin them to stand 3-5 inches apart. Most gardeners like to do this in several passes to determine the strongest plants to save. Thinning is very important to get big thick leaves.