In zone 4, sow spinach from April 4 to April 25, three to six weeks before your last spring frost, once the soil reaches about 45 °F. It is ready in about 40 days. For a fall crop, the last sowing date is about July 31.
Spinach dates for your ZIP code
Planting times based on university extension guidance (UNH, Cornell, Purdue, Minnesota, Nebraska and UMass Extension). Frost dates from NOAA 1991–2020 U.S. Climate Normals, nearest weather station. Zones derived from the 2023 USDA Plant Hardiness Zone Map data (PRISM Climate Group, Oregon State University). This is not the official USDA Plant Hardiness Zone Map.
Spinach timing in zone 4
| Task | When |
|---|---|
| Sow outside | April 4 – April 25 |
| First harvest | May 12 – June 9 |
| Sow for fall by | July 31 |
| Sow again | Every 2 weeks in spring, until the days get long |
| Thin | When leaves touch and plants are about 2 inches tall |
| Overwinter (optional) | Sow in early fall and mulch over winter |
Most of zone 4 sees its last spring frost between May 11 and May 23 (typical May 16) and its first fall frost between September 21 and September 29 (typical September 25). Spinach tolerates frost, so early sowing is safe. The tool above uses the weather station closest to your ZIP code.
Why spinach is planted early
Spinach is a cool-season crop that grows best at 50–60 °F and tolerates frost. It bolts, sending up a flower stalk and turning bitter, as the days lengthen and warm up in late spring. That is why it is sown weeks before the last spring frost, and again in late summer for fall.
Best spinach varieties for zone 4
Spinach loves the cool weather of zone 4. Choose slow-bolting varieties for spring, because lengthening days trigger bolting:
- Slow-bolting: Tyee, Olympia, Space, Acadia, Indian Summer and Tarsier.
- Hardy for overwintering: Bloomsdale Long Standing.
- Fast baby-leaf types: Tundra, Tarsier and Red Snapper, ready in under 30 days.
How to plant spinach
- Sow seeds directly in the garden, about ½ inch deep, once the soil is about 45 °F.
- Space seeds 1–4 inches apart in rows or wide beds.
- Thin when the leaves touch and plants are about 2 inches tall. Eat the thinnings.
- Sow again every two weeks for a continuous harvest.
- Keep the soil evenly moist for fast, tender growth.
Zone 4 spinach tips
- Sow as early as you can. Spinach sown once the soil is about 45 °F matures before the long days of summer make it bolt.
- Sow in small batches every two weeks in spring for a longer harvest.
- Try overwintering. Sow in early fall, let the plants grow a little before winter, and mulch them. They often regrow early in spring.
- Harvest the outer leaves to keep the plant producing, and pull the whole plant once it starts to send up a flower stalk.
Harvesting spinach
Spinach is ready in about 27–50 days, depending on the variety. Cut the full-size outer leaves and leave the center to keep growing, or cut the whole plant. Once it starts to send up a flower stalk, harvest everything, because the leaves turn bitter.
Spinach planting dates in nearby zones
See dates for every zone on the spinach planting guide, or build a full schedule with the planting calendar.
Frequently asked questions
Is it too late to plant spinach in zone 4 in May?
For spring, it is getting late: spinach sown in May runs into long days and bolts quickly. Choose a slow-bolting variety, or wait and sow for fall.
Can spinach survive winter in zone 4?
Often, with mulch. Sow in early fall so the plants grow a little before winter. Bloomsdale Long Standing is one of the hardiest.
Can spinach handle frost?
Yes. Spinach is frost tolerant and grows best in cool weather, so it is sown three to six weeks before your last spring frost.
Why does my spinach bolt?
Long days and warm temperatures in late spring trigger bolting. Sow early and choose slow-bolting varieties such as Tyee or Olympia.
How deep should spinach seeds be planted?
About ½ inch deep, 1–4 inches apart.
Sources. Planting dates use the median frost dates of each USDA zone, calculated from NOAA climate data for every ZIP code in the zone.