How to Plant Iceberg Lettuce From Seed and Transplant
Iceberg lettuce gives you those tight, crisp, pale-green heads that hold up far better than softer varieties. Here is how to plant iceberg lettuce the right way, with the spacing, timing, and soil moves I rely on each spring and fall here in Kansas.
Plant iceberg lettuce 4 to 6 weeks before your last spring frost, or in late summer for a fall crop. Sow seeds 1/4 inch deep, space plants 12 inches apart, and keep soil temperature near 60°F to 65°F.
When to Plant Iceberg Lettuce
Plant iceberg lettuce when soil temperatures sit between 40°F and 75°F, with 60°F to 65°F being the sweet spot. Iceberg is a cool-season crop (Lactuca sativa, crisphead type) that bolts fast in heat, so timing carries more weight than almost anything else you do.
In Kansas and across the Great Plains, I start spring transplants indoors 6 to 8 weeks before the last frost, then set them in the field 4 to 6 weeks before that frost date. For fall harvest, I direct seed in late July or early August once daytime highs ease off.
Check your USDA hardiness zone for your local frost dates. Northern zones (3 to 5) need a tighter spring window. Southern zones (8 to 10) often skip summer planting and grow iceberg as a fall and winter crop instead.
Learn more:How to Plant Lettuce in a Pot: Easy Container Guide
Best Soil and Site for Iceberg Lettuce
Iceberg lettuce wants loose, well-draining loam with a pH between 6.0 and 6.8. Heavy clay or hardpan slows root development and triggers tip burn, a calcium-uptake disorder that ruins head quality.
Work the bed 8 to 10 inches deep before planting. Mix in 2 to 3 inches of finished compost. If a soil test shows phosphorus or potassium running low, side-dress with a balanced fertilizer at planting. I aim for 1 to 1.5 pounds of nitrogen per 100 square feet, split across the season.
Pick a site with at least 6 hours of direct sun in spring or fall. In late spring or early summer, partial afternoon shade helps slow bolting.
How to Plant Iceberg Lettuce From Seed
Sow iceberg lettuce seeds 1/4 inch deep into moist, fine-textured soil. Press lightly. Water with a fine mist so you do not wash the seeds out.
Steps for direct seeding:
- Rake the bed smooth and remove clods larger than a marble.
- Mark rows 18 to 24 inches apart.
- Drop seeds every 2 to 3 inches in the row.
- Cover with 1/4 inch of fine soil or vermiculite.
- Water gently and keep the top inch consistently moist until germination.
Germination usually takes 7 to 10 days at 60°F to 65°F. If your soil runs warmer than 75°F, germination rates drop sharply. For more on getting reliable sprouts, my notes on germinating lettuce seeds cover the temperature and moisture tricks I use indoors.
Once seedlings hit 3 to 4 true leaves, thin to one plant every 12 inches. Do not skip thinning. Crowded iceberg never forms tight heads.
How to Transplant Iceberg Lettuce Seedlings
Transplant iceberg lettuce when seedlings have 4 to 5 true leaves and roots fill the cell, usually 4 to 6 weeks after sowing. Harden off seedlings for 7 days before setting them in the field.
Set transplants at the same depth they grew in the tray. Do not bury the crown. Water in with a half-strength starter fertilizer the same day. Cover with floating row cover for the first 10 days if temperatures swing.
If you are still deciding between seed and transplant, my walkthrough on planting lettuce from seed explains the trade-offs. I lean transplant for spring because heads form faster, and I direct seed for fall because the soil is already warm and roots establish quickly.
Spacing and Depth for Iceberg Lettuce
Space iceberg lettuce 12 to 14 inches apart in the row, with 18 to 24 inches between rows. Plant seeds 1/4 inch deep. Set transplants so the soil line on the stem matches the soil line of the cell.
Tight spacing produces small, loose heads. Wide spacing wastes ground. I run 12 inches in-row and 20 inches between rows on raised beds, and 24 inches between rows on flat field plantings. My broader notes on proper plant spacing explain how spacing affects head weight and disease pressure across crops.
Watering Iceberg Lettuce After Planting
Water iceberg lettuce to deliver 1 to 1.5 inches per week, split into 2 or 3 applications. Iceberg has shallow roots that dry out fast in Kansas wind.
Drip irrigation works best. It keeps foliage dry, cuts disease pressure, and uses 30 to 50 percent less water than overhead sprinklers. My comparison of drip versus sprinkler watering covers setup costs and trade-offs. Mulch with 2 inches of straw or grass clippings once plants are 4 inches tall. Mulch holds moisture and steadies soil temperature, which helps prevent tip burn.
Common Problems After Planting
Iceberg lettuce has predictable problems if you know what to watch for. Catch them in the first 2 weeks and you save the crop.
Damping Off
Damping off shows up as collapsed seedlings at the soil line, usually after cool, wet weather. Use sterile seed-starting mix indoors, water from below, and improve airflow. My guide on preventing damping off in young seedlings covers fixes that do not need fungicides.
Aphids and Cutworms
Aphids cluster on the undersides of new leaves and stunt growth. Cutworms slice through stems at night just above the soil. Set cardboard collars around transplants. Knock aphids off with strong water jets or use insecticidal soap. For broader strategies, the natural pest control options I use work well for market gardens.
Bolting
Bolting means the plant sends up a flower stalk before forming a tight head. Heat triggers it. Plant earlier in spring, choose heat-tolerant varieties like ‘Summertime’ or ‘Crispino’, and shade plants once temperatures top 75°F. The Penn State Extension lettuce production research lists trial-proven cultivars worth considering for hotter zones.
Tip Burn
Tip burn shows up as brown, dry edges on inner leaves. It comes from uneven calcium uptake, almost always tied to water stress. Steady watering and 2 inches of mulch fix most cases.
How Long Until Iceberg Lettuce Is Ready
Iceberg lettuce takes 70 to 85 days from seed to harvest, or 55 to 70 days from transplant. Harvest when heads feel firm and dense, like a regulation softball, and the outer wrapper leaves curl slightly.
Cut heads at the base with a sharp knife in the cool morning hours. Pull off the loose outer leaves, then refrigerate within 2 hours of cutting. Properly harvested iceberg holds 2 to 3 weeks in cold storage at 32°F to 34°F.
Bottom Line for Your Iceberg Patch
Iceberg lettuce rewards good prep more than fancy inputs. Get your soil to pH 6.0 to 6.8, hit the planting window 4 to 6 weeks before last frost, space plants 12 inches apart, and keep the water steady. Do those four things and you will pull tight, sweet heads off your ground every spring and fall.
