Popeye knew what he was talking about! Spinach is a nutritional powerhouse and when picked fresh from the garden, much more delectable than from a can. This fast-growing green is easy to grow and thrives in cool weather. Spinach does well in mild spring weather, but its harvest season is limited by the combination of increasing day lengths and temperatures as summer approaches. These environmental changes trigger bolting, or going to seed, making the leaves taste bitter. The shortening days and cooler weather of fall don’t trigger bolting, making spinach a great crop for an extended fall harvest in many parts of the country.
Varieties: Spinach varieties fall into three main categories: those with smooth leaves, those with crinkled or savoyed leaves, and those with semi-savoyed leaves. Smooth-leaved varieties are tender and easy to clean, making them perfect for salads. Savoy-leafed varieties hold up better when cooked. Look for varieties that show good disease resistance. Select varieties with good bolt resistance and heat tolerance for late spring sowings and those with good cold hardiness for fall harvests.
Site: Full sun (at least 8 hours of direct sun/day) is generally best, but spinach will still yield a respectable harvest with only 4-6 hours of sun. Light shade during warm weather will help to keep spinach producing longer.
Soil: Plant in fertile, well-drained soil enriched with plenty of compost or other organic material. Spinach does best at soil pH between 6.5-7.
When to Plant: Spinach seeds can be planted directly in the garden as soon as the soil can be worked in the spring. For an extra-early spring harvest, you can also plant seeds in a prepared bed about a month before the first hard frost the fall before. Protect the young seedlings with a thick mulch of straw or shredded leaves in late fall; uncover early the following spring. For fall crops, plant seeds about 2 months before your expected fall hard frost date. In mild winter climates, you can make repeat sowings every few weeks throughout the fall.
Planting: Plant in wide rows or beds. When the seedlings are a couple of inches tall, thin first to 2 inches apart, then 4, and finally 6 inches, enjoying your tender thinnings in salads as you go.
Culture: Be sure to keep the soil consistently moist to keep leaves from becoming bitter. A layer of mulch around plants will conserve soil moisture and keep weeds down as well. Give your plants a dose of soluble fertilizer such as fish emulsion when they are about a month old.
Troubleshooting: Leafminers are flies that lay their eggs inside spinach leaves. The larvae that hatch out tunnel though the leaves as the feed, leaving white blotches. The easiest way to foil this pest is to cover the seedbed with a floating row cover as soon as seeds are planted and keep the cover in place throughout the growing season. Keep weeds down as some, such as pigweed, can be host to leafminers. Handpick and destroy any infested leaves as soon as you see them. Rotate the location of your spinach (and related beets) in the garden to avoid insects that have overwintered in the soil. To avoid disease problems, look for varieties that are resistant to downy mildew and fusarium wilt.
Harvesting: You can start picking spinach leaves as soon as leaves are about 6 inches long and the plant has about 8 leaves. Pick only some of the outer leaves and your plants will continue to keep producing. You can also harvest entire plants by cutting off the plant at ground level. This is a good tactic when the spring growing season is ending and plants are about to bolt.