How to Grow Spinach: From Sowing to Harvest

Spinach has a reputation for being difficult, and it's half deserved — sow it at the wrong moment and it shoots straight to seed, leaving you with a bitter rosette and a flower stalk. But spinach isn't difficult; it's punctual. It is a cool-season crop with an internal clock set by temperature and day length, and once you work with that clock instead of against it, it becomes one of the fastest, most productive things in the garden: six weeks from seed to plate, and it will regrow after cutting several times over.

When to sow: the whole game

Spinach germinates best in cool soil — it sprouts happily at soil temperatures from about 7°C and gets increasingly unreliable once the soil passes 21°C, when the seed can simply refuse to germinate at all. Combine that with its habit of bolting in heat and long days, and the calendar writes itself: sow in early spring as soon as the soil can be worked, then again in late summer and early autumn for a second, often better, crop. Midsummer sowings of ordinary spinach are usually wasted seed.

• Spring crop: sow every two weeks from the moment the soil thaws until about a month before warm weather settles in.
• Autumn crop: sow six to eight weeks before your first expected frost — in most temperate gardens that means mid-August through September. The soil is warm enough for fast germination and the shortening, cooling days are exactly what spinach loves.
• Winter harvests: in mild regions, a September sowing under fleece, a cold frame or a low tunnel will produce sweet leaves through winter — cold actually concentrates the sugars.
• Overwintering: sow late so plants reach a few true leaves before deep cold, mulch, and they'll explode into growth first thing in spring.

Soil and position

Spinach is a leaf crop in a hurry, and it wants fuel: fertile, well-drained soil with plenty of compost and a pH around 6.5–7. It struggles in strongly acidic soil. Full sun is ideal in the cool seasons; for late-spring sowings, a spot with light afternoon shade buys you an extra week or two before bolting. Raised beds and containers work well — spinach roots are relatively shallow, and a 20 cm-deep pot on a balcony grows a respectable salad's worth.

Sowing and spacing

Sow seed directly where it will grow — spinach resents transplanting from open trays, though module-raised seedlings moved young work fine. Sow 1–2 cm deep, about a seed every 2–3 cm in rows 25–30 cm apart, and firm the soil gently. Seedlings appear in 5–14 days depending on temperature. When they have two true leaves, thin to 8–10 cm apart for baby leaf, or 15 cm for full-size plants — and eat the thinnings, which are perfect in salads.

Tip: spinach seed loses vigour quickly in storage. Use fresh seed each year or oversow generously with older packets, and refrigerate seed for a week before a late-summer sowing in warm soil to improve germination.

Watering and feeding

Consistent moisture is the difference between tender, mild spinach and tough, bitter, bolt-prone spinach. Water regularly — dry spells are a bolting trigger — and mulch between rows to keep the root zone cool and even. In good soil spinach rarely needs extra feeding, but if growth is pale and slow, a nitrogen-rich liquid feed once plants are a third grown gets the leaves moving again.

Bolting: what triggers it and how to delay it

Bolting — the sudden vertical flower stalk and arrow-shaped leaves — is spinach's response to heat above roughly 24°C, days longer than about 14 hours, and stress from drought or overcrowding. You can't stop a bolting plant, but you can delay the trigger: sow at the right season, choose slow-bolting varieties for the risky shoulder months, keep plants watered and thinned, and use afternoon shade in warm spells. Once a plant does bolt, pull the whole thing and use the leaves that are still tender the same day.

Pests and problems

• Leaf miners: pale winding tunnels inside the leaf. Pick off and destroy affected leaves; fine insect mesh over the crop from sowing prevents the fly laying at all.
• Downy mildew: yellow patches on top of the leaf with grey-purple mould beneath, worst in cool damp weather on crowded plants. Space properly, water the soil rather than the foliage, and choose resistant varieties.
• Slugs and snails: seedlings can vanish overnight — protect young rows, especially in autumn.
• Birds: pigeons love spinach seedlings; netting or mesh solves it.

Harvesting: cut and come again

Start picking as soon as leaves are big enough to bother with — usually five to seven weeks after sowing. Take the outer leaves first, a few from each plant, and the central rosette keeps producing for weeks. For baby leaf, cut whole rows 3 cm above the crown with scissors and they'll regrow two or three times. Harvest in the cool of the morning for the crispest leaves, and eat or refrigerate quickly; spinach wilts fast but also revives impressively in a bowl of cold water.

Warning: don't confuse true spinach (Spinacia oleracea) with the heat-tolerant lookalikes sold as 'summer spinach'. New Zealand spinach and Malabar spinach are fine crops, but they are different plants with different needs — and unlike true spinach, New Zealand spinach should always be blanched before eating in quantity due to its higher oxalate levels.

Growing something you can't identify, or leaves showing spots you can't place? Point PlantMe at the plant — the app identifies vegetables and their diseases alike, so you know whether you're looking at downy mildew or just splashed mud before you act.