Keep the plants well watered. Mulch with straw, hay or shredded leaves to help conserve moisture and keep the roots cool. Keep the plants well weeded; if using a hoe, just scratch the surface to avoid damaging the roots. Maximize air circulation by not overcrowding.
When the plants are half grown (three to four weeks), feed with compost tea, made by soaking a bag of compost overnight in a pail of water. If they're growing slowly and leaves are pale, feed with additional compost tea or an organic fertilizer. While spinach needs a good supply of nitrogen for heavy yields of dark green leaves, too much nitrogen can result in the production of excess nitrates, which could pose a health risk if too much is ingested.
Once spinach plants have bolted, pull them out and replant the bed with a heat-loving crop such as beans. Don't try to grow spinach in the long, hot days of summer. For fall crops, plant eight weeks before the first hard frost to produce good-sized plants before the days become too cold for further growth. Since spinach doesn't germinate well in soil temperatures above 24°C, you may need to keep the seedbed cool by watering it daily, shading it with a cloth or covering the seeds with a board until they germinate.
Harvesting and storage
Spinach is ready for harvesting six to eight weeks after planting, depending on the variety and the weather. The colder the weather, the slower the growth. Start picking when there are at least six large leaves on the plant, harvesting the outside leaves before they become too large. As it grows, up to half the plant can be harvested at once. Discard any yellow or wilted leaves. Wrap unwashed leaves in damp paper towels and store in a plastic bag in the refrigerator. Use within three days.