When to sow spinach

Spinach is a cool-weather crop with two seasons. Sow the spring crop outdoors from March, as soon as the soil can be worked, until about mid-May. Seed germinates in soil as cold as 36°F, just slowly; at 59–68°F it is up within a week.

Skip the summer. Spinach flowers in response to long days, and heat and dry soil speed that up, so sowings from late May to July tend to bolt before they give you much.

The second season starts in August. Sowings from August to mid-September give autumn leaves from late October and, with hardy varieties, plants that stand through winter and start growing again in early spring. In mild areas you can sow into early October.

Spinach is normally sown straight into the bed; it doesn't need starting indoors. Sow in drills about 0.8–1.2 in deep with 8–12 in between rows, and keep the soil moist until the seedlings are up.

Thin the seedlings in stages: to about 3 in if you want baby leaves, to 6 in for full-sized plants. Eat the thinnings.

A 120 × 80 cm raised bed takes four rows 8 in apart with plants every 6 in, about 32 plants. For baby leaves you can sow the same rows more thickly.

Spinach is thirsty. Keep the soil evenly moist, especially in spring dry spells, and water in the morning rather than the evening so the leaves dry off before night.

Work some compost into the bed before sowing, but don't overdo the nitrogen. Too much makes soft leaves and raises their nitrate content, which is highest in fast, heavily fed spinach.

Overwintering spinach is hardy, but hard frost without snow cover damages the leaves. Lay fleece over the row in cold spells, or grow the winter crop under a cloche or in a cold frame from October.

Baby leaves are ready about four weeks after sowing, full plants after eight to ten weeks. Pick the outer leaves as you need them, or cut whole plants about 1 in above the soil and let them regrow.

Winter spinach can be picked from late October through mild spells in winter. Cut carefully so you don't damage the heart, and the plants will sprout again in spring.

Once a flower stalk starts to rise in the middle, the leaves turn bitter quickly. Harvest the whole row then and clear the space for the next crop.

Downy mildew is the main disease: yellow patches on the upper side of the leaf with fuzzy mould underneath, most of all in humid weather and crowded rows. Thin properly, water in the morning and choose resistant varieties. The fungus keeps forming new races, so look for varieties resistant to as many as possible.

Slugs love soft young spinach, and birds sometimes pull seedlings. Protect young rows with fleece or netting and check for slugs after rain.

Spinach belongs to the amaranth family with beetroot and chard, which share some pests and diseases. Leave three to four years before any of them grows in the same bed again.

Spinach grows fast and is off the bed by early summer, so it fits well before or between crops planted later, such as tomatoes, beans or courgettes. That is simple use of space, and it works.

Mixed-planting tables also claim that spinach roots improve the soil for its neighbours. We found no solid evidence for that; treat it as tradition. What matters is rotation: don't follow spinach with beetroot or chard.