Iowa · zones 4b–6a
When to plant spinach in Iowa.
Sow between Mar 10 to Apr 21 in a typical year, keyed to Iowa's median last frost around May 1. A second, fall sowing fits Jul 24 to Sep 11. Dates below are state medians; your ZIP code shifts them by days to weeks.
The 2026 windows
Spinach dates for a typical Iowa season.
Direct sow
Mar 10 to Apr 21
Keyed to the ~May 1 last frost. Sow 0.5" deep, 3" apart.
Fall round
Jul 24 to Sep 11
Counted back from the ~Oct 7 first frost.
Harvest
~42 days later
~0.25 lb per plant over ~1 weeks.
Iowa spans more than one climate: Zone 5 is the most common zone, but the state runs 4b to 6a. That's why the planner works from your ZIP code's frost dates, not your zone: mountain and coastal gardens in the same state can be three weeks apart.
In Iowa: watch for
The pests that find spinach here.
A middle-length season, about 159 frost-free days, means spinach overlaps leaf miners for a stretch each summer. Check plants every week or two and treat early.
Winding pale tunnels or blotches inside the leaves.
Organic fix: Pick and destroy mined leaves; cover the row.
Cercospora leaf spot
Round spots with gray centers and a red-purple rim, oldest leaves worst.
Organic fix: Space wider so leaves dry fast, clear old debris, and pull pigweed and lambsquarters nearby.
Your season math: Iowa gives spinach about 159 frost-free days, and it needs roughly 42 days to a first harvest. That fits about 17 re-sown rounds across the season, so you can keep it coming instead of picking once.
Planting spinach in Iowa: questions
When should I plant spinach in Iowa?+
In a typical Iowa year, sow spinach between Mar 10 to Apr 21, keyed to the state's median last frost around May 1. There's also a fall window: Jul 24 to Sep 11. Your exact dates shift with your ZIP code and microclimate.
What USDA zone is Iowa?+
Iowa spans zones 4b–6a, mostly zone 5. But frost dates, not zones, set planting time. The free planner uses your ZIP code's actual frost dates.
How many spinach plants do I need?+
Depends who you're feeding. The crop page has exact counts per household size, or the free planner does the math for your family in about 60 seconds.