How To Grow Spinach
Grow Spinach to produce large yields of vitamin-rich, dark green leaves that are excellent for salads and for cooking. A cool-weather crop, the secret to success with this crop is to start sowing seeds as soon as possible in spring, to make small, frequent plantings during late spring and summer, and to concentrate on fall as the season for the main crop.
The Soil and Planting
Spinach grows most quickly in well-drained soil rich in organic matter such as compost or composted manure and with a pH of 6.5 to 7. In order to grow spinach twice a year, plant it about 4 to 6 weeks before the last frost in the spring, and again 6 to 8 weeks before the first frost in the fall. Space plants 12 inches apart; this gives leaves room to reach full size. One easy growing option is to plant spinach in pots filled with premium quality potting mix which will provide roots with just the right environment for strong growth.
When spinach begins to bolt in warm weather, it tastes bitter and is ready to be pulled. The plants look tall and spindly with thick stalks when they start flowering.
In the spring, plants will grow tall and bloom (called bolting) as soon as the days are longer than 14 hours. Heat also speeds up bolting, since spinach prefers temperatures between 35 and 75 degrees.
Because of bolting, spinach is an especially popular crop for fall, when days are short and cool. Plants are very cold-hardy, tolerating temperatures as cold as the teens to low 20s once they are well established. This quality makes them great for overwintering over in zones 8 and southward.
In cold climates, many plant spinach in a cold frame or cover plants with hay and leave them all winter.
When to Harvest
Spinach leaves are ready to harvest as soon as they are big enough to eat. Harvest by removing only the outer leaves and allowing the center leaves to grow larger; this will allow the plant to keep producing. Picking the outer leaves also gives the advantage of briefly delaying bolting. In spring, when plants are about to bolt, pull the entire plant at once to enjoy the leaves before they become bitter.