When to Plant Lettuce in Iowa
Published: April 21, 2026
Iowa gardeners in Zone 5b have a 28-week frost-free window for lettuce (April 7 to October 22). Cool-season crops like lettuce do well here because the short, cool summers match the plant's temperature preferences naturally. This guide gives exact dates for Iowa based on your local frost calendar.
Lettuce Planting Dates for Iowa
| Start seeds indoors | March 10–17 |
| Last frost (average) | April 7 |
| Transplant outdoors | March 10–20 |
| Direct sow outdoors | February 24–March 6 |
| Expect first harvest | April 9 – May 9 |
| Fall crop start | September 10–20 |
| Fall harvest | October 10 |
| First fall frost (average) | October 22 |
Growing Lettuce in Iowa's Climate
Iowa's cold Zone 5b climate is close to ideal for lettuce. The cool springs and moderate summers match the plant's natural temperature preferences, producing crisp, sweet, slow-bolting harvests that hot-climate gardeners cannot grow.
The fall lettuce crop in Iowa is often better than the spring crop. Plants mature as temperatures cool in September and October, concentrating sugars and tightening heads or roots. Light frost can improve flavor; hard frost signals harvest time.
Common lettuce pests to watch for in Iowa include Aphids and Slugs. The first line of defense is companion planting: Carrot and Radish planted nearby discourage several of these pests by confusing host-plant identification or repelling adults before they can lay eggs. Weekly garden walks in the early morning catch problems when they're still manageable.
Lettuce Garden Calendar for Iowa
| Month | Task | Notes |
|---|---|---|
| January | — | Dormant season |
| February | Direct sow seeds | Sow seeds 1/4–1/2 inch deep, 8 inches apart |
| March | Transplant outdoors | Soil temp must be 40°F+; nighttime lows above 50°F |
| April | Harden off seedlings | Set seedlings outdoors 1–2 hours daily, increasing gradually |
| May ← | Watch for bolting | Harvest promptly; spring heat arrives quickly |
| June | — | Dormant season |
| July | — | Dormant season |
| August | — | Dormant season |
| September | Fall crop planting | Transplant or direct sow for fall harvest before frost |
| October | First frost approaches | Harvest remaining lettuce; cover plants on frost nights |
| November | — | Dormant season |
| December | — | Dormant season |
Lettuce Growing Tips for Iowa Gardeners
- •Direct sow very shallowly — lettuce seeds need light to germinate; cover with just 1/8 inch of soil.
- •Cut outer leaves 1 inch above the crown for "cut-and-come-again" harvests lasting weeks.
- •Iowa's short growing season means start seeds indoors under grow lights — don't rely on windowsill light which produces leggy, weak seedlings that struggle outdoors.
- •Cover young transplants with floating row covers for the first 2–3 weeks outside. The 3–5°F of protection reduces frost damage risk and accelerates early growth.
- •Provide afternoon shade in warmer climates (Zones 7+) to extend the spring window before heat bolts plants.
Companion Planting for Lettuce in Iowa
In Iowa's cold climate, planting lettuce with Carrot and Radish helps deter pests and improve soil. Avoid planting near Fennel and Celery, which inhibit lettuce growth through root chemistry or shared pest pressure. See the full lettuce companion planting guide for the complete list.
Lettuce Planting Dates by City in Iowa
Top cities in Iowa — select for city-level frost dates and planting calendars.
Frequently Asked Questions
When should I plant lettuce in Iowa?
In Iowa (Zone 5b), start lettuce seeds indoors around March 10–17 and transplant outdoors around March 10–20 — 4 weeks before the state's average last frost of April 7.
What is the last frost date in Iowa?
Iowa's average last frost date is April 7 in the state's most common Zone 5b. Frost dates vary by city — higher elevations and northern counties run 1 to 3 weeks later than the state average. See the city list below for city-level frost dates.
Can I grow lettuce year-round in Iowa?
lettuce is a cool-season crop in Iowa, with spring and fall windows. Summer heat bolts the plants before they can produce a harvestable crop. Succession planting every 2–3 weeks stretches the harvest window.
What lettuce varieties grow best in Iowa?
For Iowa's Zone 5b, Cold-tolerant Buttercrunch, Winter Density, and Arctic King overwinter with protection.
When do I start lettuce seeds indoors in Iowa?
Start lettuce seeds indoors in Iowa around March 10–17, which is 4 weeks before the state's average last frost of April 7. Use grow lights and keep soil temperatures at 70–75°F for fastest germination.