Iowa · zones 4b–6a
When to plant lettuce in Iowa.
Sow between Mar 24 to May 8 in a typical year, keyed to Iowa's median last frost around May 1. A second, fall sowing fits Jul 24 to Sep 22. Dates below are state medians; your ZIP code shifts them by days to weeks.
The 2026 windows
Lettuce dates for a typical Iowa season.
Direct sow
Mar 24 to May 8
Keyed to the ~May 1 last frost. Sow 0.25" deep, 6" apart.
Fall round
Jul 24 to Sep 22
Counted back from the ~Oct 7 first frost.
Harvest
~45 days later
~0.4 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.
Iowa growing notes
Iowa lettuce has a short window before summer heat shuts it down.
The spring window closes faster here than the calendar suggests
Iowa's last frost lands around May 1 on average, but real summer heat, the kind that pushes lettuce to bolt and turn bitter, often arrives within weeks after; the statewide average of 159 frost-free days sounds generous, but most of that count sits on the hot side of the calendar, well past lettuce's cool sweet spot. Sow the first round as soon as the soil can be worked in spring, even under light frost risk, since lettuce germinates and grows fine well below the temperatures that would stop a warm-season crop, and every early week gained is a week of harvest before the heat cuts the spring run short.
Space seed 6 inches apart, a quarter-inch deep, and choose a loose-leaf type for the earliest sowings rather than a slow-heading romaine, since a cut-and-come-again leaf crop gets you eating in as little as 30 days instead of the full 45 a head needs to finish.
Skip the hottest weeks on purpose
Because lettuce matures in about 45 days and shrugs off light frost on both ends, an Iowa garden can keep new rows coming from the moment the soil can be worked in spring clear into fall. The sharpest version of that schedule builds in a deliberate gap: stop starting new rows once real heat sets in and hold off until it breaks, because anything sown into the heart of Iowa's hot, muggy midsummer bolts to seed before it is worth eating no matter the variety.
Shade cloth over the row for the later sowings that do land in warmer weather, and a spot with afternoon shade from taller crops like sweet corn, buys a lettuce planting an extra week or two before it bolts. The final rounds, sown for a harvest running right up to the fall frost, are typically the sweetest and most tender of the whole year, since cooling temperatures slow bolting and let the leaves build sugar instead of stem.
Cutworms at planting, slugs after rain
Cutworms are the spring threat: a caterpillar that hides just under the soil surface by day and severs young seedlings at the base overnight, often taking out an entire freshly thinned row in one pass. A cardboard collar pushed an inch into the soil around each seedling, or transplants instead of direct seed for the first round, sidesteps the problem entirely while the bed is at its most vulnerable.
Slugs and snails become the bigger issue after a wet Iowa stretch, especially in a bed with straw mulch or crop residue nearby for cover; check the underside of leaves at dusk, when slugs are actively feeding, and hand-pick into soapy water rather than relying on bait alone. Aphids show up too, but rarely need more than a hard spray of water to knock them off before they build a real colony on the tender new growth.
In Iowa: watch for
The pests that find lettuce here.
A middle-length season, about 159 frost-free days, means lettuce, leaf overlaps aphids for a stretch each summer. Check plants every week or two and treat early.
Clusters tucked into the heart of the head.
Organic fix: Rinse well; insecticidal soap on young plants.
Ragged holes and slime trails, worse after rain.
Organic fix: Iron-phosphate bait; a diatomaceous-earth ring; hand-pick at night.
Seedlings clipped off at the soil line overnight.
Organic fix: Collars around the stems; Bt or diatomaceous earth.
Pale yellow patches boxed in by the leaf veins, with white fuzz underneath.
Organic fix: Give plants room, let them dry between waterings, clear old leaves, and pick resistant varieties.
Your season math: Iowa gives lettuce about 159 frost-free days, and it needs roughly 45 days to a first harvest. That fits about 12 re-sown rounds across the season, so you can keep it coming instead of picking once.
Planting lettuce in Iowa: questions
When should I plant lettuce in Iowa?+
In a typical Iowa year, sow lettuce between Mar 24 to May 8, keyed to the state's median last frost around May 1. There's also a fall window: Jul 24 to Sep 22. 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 lettuce 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.