How to Grow Spinach

Why spinach bolts, and how to dodge it

Spinach is programmed to flower when days get long and temperatures rise. Utah State Extension states it bolts during the long days and warm temperatures of summer, and that high summer heat reduces growth, hurts quality, and pushes plants to flower. Once a spinach plant bolts, the leaves turn bitter and the crop is over.

You cannot stop bolting in midsummer, so you work around it with timing. Grow spinach in the cool ends of the season — early spring and fall — and, for spring, choose 'long-standing' or slow-to-bolt varieties that buy extra time before warm weather hits.

The fall crop is often the easiest: sown in late summer, it grows into shortening days and cooling weather and simply does not bolt. Succession-sowing every couple of weeks in spring stretches the harvest until heat ends it.

Sowing in cool soil

Spinach germinates in cold ground. Seed can be sown once soils reach 40°F, about 2 to 3 weeks before the last spring frost, planted 1/2 inch deep; it germinates best at 55 to 65°F and takes 7 to 10 days to emerge. Soil above 80°F actually suppresses germination, which is another reason midsummer sowings fail.

For fall, count back and sow roughly 50 to 75 days before your target maturity date so plants bulk up as the weather cools. Thin seedlings to about 3 inches apart in rows around 12 inches apart.

Keep the bed evenly moist and growing steadily. For exact planting dates, spacing, watering, and fertilizer numbers, the spinach calculators cover each point.

Cold tolerance, overwintering, and harvest

Cold is where spinach shines. Young plants are not seriously damaged by temperatures down to 32°F, and the fall crop keeps producing well past the first light frosts. This hardiness is the flip side of its heat intolerance.

Better still, spinach overwinters. Utah State notes a plant that forms 4 to 5 true leaves late in the year will easily over-winter, resuming growth in spring for the earliest possible harvest — a light mulch helps borderline plants through. In milder regions this needs no protection at all.

Harvest is flexible: pick individual outer leaves anytime before the flower stalk forms, or cut the whole plant off to within about 2 inches of the soil and let it regrow. Take leaves young and tender; older leaves near bolting time turn bitter.

Sources

Reviewed 2026-07-18. We cite university Extension, government, and established horticultural sources — and never invent pesticide rates or dangerous treatments.

• Utah State University Extension — How to Grow Spinach in Your Garden — Spinach flowers (bolts) during long days and warm temperatures in summer, and high summer temperatures reduce growth and quality and cause flowering; sow seed 1/2 inch deep 2-3 weeks before the last frost once soils reach 40°F; seeds germinate best at 55-65°F, take 7-10 days, and germination is reduced above 80°F; plant fall crops 50-75 days before anticipated maturity; space 3 inches between plants in rows 12 inches apart; temperatures down to 32°F do not seriously damage young plants; spinach over-winters if the plant has 4-5 true leaves late in the year; pick individual leaves before the flower stalk forms or cut all leaves to within 2 inches of the soil.
• Illinois Extension — Spinach (Home Vegetable Gardening) — Spinach is grown as a spring and a fall crop; it bolts quickly during the long days of late spring and summer, and warm temperatures accelerate bolting; spinach planted in late summer for a fall crop grows under shortening days and will not bolt; long-standing, slow-to-bolt varieties are best for spring planting; cold-tolerant varieties can over-winter for an early spring harvest.

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