Spinach is one of the fastest and most rewarding leafy vegetables, but it has a quirk that trips many people up: it does not tolerate long summer days. Whoever sows it in June or July usually harvests only flower stalks instead of leaves. The solution lies in the right timing.
Spinach knows two seasons in which it likes to grow: spring and late summer to autumn. In both the days are shorter and the temperatures milder, exactly what it needs. This article explains the two sowing windows and how you harvest well in both.
Two windows, one enemy: the long day
Spinach is a long-day plant. As soon as the days in late spring exceed a certain length, it switches from leaf formation to flowering. It bolts, turns bitter, tough and inedible. That is why there is the one big hole in summer in which sowing is not worthwhile.
The two good times are spring from about March to April and late summer to autumn from August to September. The autumn spinach is especially valuable: sturdy varieties overwinter and deliver as early as March, long before all others, the first fresh harvest.
The three growing times at a glance
- Spring spinach (March to April)
The quick harvest for spring. Sown straight into the bed, it is ready in six to eight weeks, before the long days make it bolt.
- Autumn spinach (August to September)
The second harvest of the year. In shorter days it grows briskly and tender and delivers into late autumn.
- Winter spinach (overwintering)
Late autumn sowing with winter-hardy varieties. It overwinters as a small rosette and delivers the earliest harvest of the next year, as early as March.
- Choose bolt-resistant varieties
For the edge times there are varieties labelled as bolt-resistant. They withstand the long day longer and extend the usable window.
How you sow spinach
Sow in the right window
Spring spinach from March, autumn spinach from August. Leave out the high summer, there it only bolts.
In rows straight into the bed
Sow about 2 to 3 centimetres deep in rows 20 centimetres apart. No raising is needed, spinach is sown direct.
Keep cool and moist
Keep evenly moist, that keeps the leaves tender and slows bolting. A half-shady spot in the edge times helps.
Harvest young and continuously
Pluck the outer leaves or cut the young rosette before the flower stalk forms. Harvesting regularly keeps the plant tender.
Spring and autumn yes, high summer no. Whoever avoids the long day and keeps it cool and moist harvests tender leaves twice a year.
The core rule for spinach
Frequently asked questions
When do you sow spinach?
In two windows: in spring from March to April and in late summer from August to September. The high summer is left out, because spinach bolts in long days. With winter-hardy varieties an overwintering autumn sowing is possible too.
Why does my spinach bolt and form flower stalks?
Spinach is a long-day plant. As soon as the summer days are long enough, it switches from leaf to flower, bolts and turns bitter. That is why you sow it not in high summer but in spring and autumn, and choose bolt-resistant varieties for the edge times.
Can spinach overwinter?
Yes, with winter-hardy varieties. Late autumn sowing overwinters as a small rosette in the bed and delivers the earliest harvest of the next year, often as early as March. In hard frost a thin layer of brushwood or fleece protects it.
Do I have to raise spinach indoors?
No, spinach is sown straight into the bed. It germinates fast and grows briskly, raising it indoors is not worthwhile. More important than the raising is the right sowing window and a cool, moist spot.
How do I keep the nitrate content in spinach low?
Do not over-fertilise, harvest on a sunny afternoon rather than a dull morning and prefer young leaves. Spinach stores nitrate in low light and with much nitrogen. Tender, young leaves from a leanly fertilised bed are the mildest.
