Spinach has become a favorite among home gardeners, who can go out each night and harvest just the amount that they need for a nice supper salad. It reaches edible maturity in 37 to 45 days and thrives best during the cool, moist seasons of the year. It can withstand hard frosts and temperatures as low as 20 F. Spinach can be grown on a variety of soils, but the best is a fertile sandy loam high in organic matter. The soil pH should range between 6.4 to 6.8. Spinach is very sensitive to acid soils, but if the pH is too high, leaves may have a yellow color referred to as chlorosis.
Spinach requires a high level of fertility, especially nitrogen.
Early spring spinach may require larger quantities of fertilizer than fall crops. Spinach, like beets and a few other crops, requires a lot of boron. Boron deficient spinach has dark roots and numerous small, flattened, yellow leaves and is generally stunted. An application of 1 oz of Borax per 100 square feet of row, broadcast prior to seeding, should prevent that problem. If the leaves have a blotchy appearance, chances are that spinach leaf miners have invaded the plant.