Quick Growing Facts

When & Where to Grow Iceberg Lettuce

Iceberg lettuce needs cool temperatures and a fairly long, steady growing period to form tight heads. It’s best suited to spring and fall, or cool-summer climates.

• Spring: Sow 2–4 weeks before your average last frost date, once soil is at least 40–45°F (4–7°C).
• Fall: Sow 8–10 weeks before expected hard frost so heads can mature in cool weather.
• Mild climates: Grow in fall, winter, and early spring; avoid peak summer heat.
• Location: Garden beds, raised beds, and containers (at least 20–25 cm deep) in full sun to very light shade.

Soil Preparation

Because iceberg forms dense heads, it needs rich, well-prepared soil so plants can grow steadily without stress.

• Loosen the top 8–10 in (20–25 cm) of soil and remove weeds, roots, and stones.
• Mix in plenty of compost or well-rotted manure for fertility and moisture retention.
• Rake the surface into a fine, crumbly seedbed so small seeds make good contact with the soil.
• If soil is very acidic, a light application of garden lime can improve vigor and flavor.
• Ensure good drainage; if soil is heavy clay, use raised beds or add lots of organic matter.

Direct Sowing Iceberg Outdoors

Direct sowing works, but because iceberg needs a long, cool season, many gardeners prefer to start plants indoors and transplant. In cool climates, you can still direct sow successfully.

1. Timing: Sow 2–4 weeks before last frost in spring, and again in late summer for fall harvest.
2. Prepare the bed: Rake the soil surface smooth and fine after loosening and enriching with compost.
3. Sowing depth: Sow seeds very shallowly, about 1/8–1/4 in (0.3–0.6 cm) deep; lettuce seeds germinate best when not buried too deeply.
4. Row spacing: Space rows 12–18 in (30–45 cm) apart.
5. Seed spacing: Sow seeds about 1 in (2–3 cm) apart; you’ll thin later to the final spacing.
6. Water: Water gently with a fine spray and keep the top layer consistently moist until seedlings emerge.

Starting Iceberg Lettuce Indoors (Recommended)

Starting iceberg indoors gives a head start and helps ensure heads mature before hot weather arrives.

• Sow 4–6 weeks before your last expected frost date.
• Use plug trays or small pots with a fine, well-draining seed-starting mix.
• Sow 2–3 seeds per cell at 1/8–1/4 in (0.3–0.6 cm) deep or pressed into the surface; thin to one strong seedling.
• Keep at 60–70°F (15–21°C) with even moisture and bright light to avoid leggy seedlings.
• Harden off seedlings for about a week before transplanting outdoors.

Thinning, Spacing & Transplanting

Adequate spacing is crucial for iceberg so the heads can close and firm up without crowding or disease.

• Thin direct-sown seedlings when they reach 1–2 in (2.5–5 cm) tall.
• For full heads, thin or transplant to 10–12 in (25–30 cm) between plants in rows 12–18 in (30–45 cm) apart.
• For baby-leaf production, plants can be spaced more closely, around 4–6 in (10–15 cm) apart or in dense bands.
• Transplant on a cool, cloudy day or in the evening; plant at the same depth as in the tray and water in well.
• Use thinnings as tender baby salad greens.

Succession Sowing for Reliable Heads

Iceberg takes longer to mature than loose-leaf types, but you can still stagger plantings for a series of harvests.

• Make two or three sowings a few weeks apart in spring, and again ahead of fall, rather than one large planting.
• In warm regions, focus on early spring and late-summer sowings so heads mature in cooler weather.
• Harvest or remove plants that begin to bolt and replace with new transplants or sowings.

Watering & Feeding

Steady moisture and moderate fertility are essential for firm, crisp heads without bitterness or tip burn.

• Watering: Keep soil evenly moist but not waterlogged. Avoid cycles of very dry then very wet soil, which can stress plants.
• Mulch: A light mulch of compost or straw helps retain moisture, suppress weeds, and keep soil cool.
• Feeding: In rich soil, compost at planting is often enough. In poorer soils or containers, use a balanced organic fertilizer or compost tea once or twice during the season.

Pests & Diseases

Iceberg is a bit more sensitive than loose-leaf lettuces, but most problems can be prevented with good spacing, clean soil, and regular monitoring.

• Slugs & snails: Common in cool, damp weather. Use traps, barriers, and hand-picking; avoid heavy mulch around the crown.
• Aphids: Check the inner leaves and head; rinse off with water or use insecticidal soap if infestations build up.
• Leaf miners & chewing insects: Remove damaged leaves and use row covers if needed.
• Tip burn: Brown edges on inner leaves can be caused by inconsistent moisture or rapid growth in heat; keep soil evenly moist and avoid overfertilizing with high nitrogen.
• Fungal diseases (downy mildew, rot): Ensure good airflow, water at soil level, and avoid wetting foliage late in the day. Remove severely affected plants.
• Bolting: Hot weather and drought cause rapid bolting and bitterness; use shade cloth and focus on cool-season harvests.

Harvesting Iceberg Lettuce

Baby Leaves & Loose Cuttings

• Begin harvesting baby leaves 3–4 weeks after sowing, when they are 2–4 in (5–10 cm) long.
• Use scissors to cut outer leaves, leaving the center to grow, or shear plants 1–2 in (2–5 cm) above the soil in dedicated baby-leaf beds.
• Baby leaves are mild and tender, perfect for mixed salads.

Tight Heads

• Iceberg is ready when the head feels firm and solid when gently squeezed, usually 70–85 days from sowing.
• Cut the entire head at the base with a sharp knife, just above the soil line.
• Harvest in the cool of the morning for maximum crispness and storage life.
• Do not wait too long; overmature heads can split or become bitter, especially in hot weather.

Storing & Using Iceberg Lettuce

• Remove any damaged outer leaves, rinse the head or leaves in cool water, and dry thoroughly.
• Store whole heads or torn leaves in a breathable or lightly sealed container/bag in the refrigerator.
• Use within about 7–10 days for best quality and crunch.
• Enjoy in salads, sandwiches, burgers, tacos, and lettuce cups; its crisp texture also holds up well in chopped salads.

Saving Seed from Iceberg Lettuce

Lettuce is mostly self-pollinating, so saving seed is straightforward, though different lettuce varieties can still cross if flowering together.

• Select healthy, vigorous plants and allow them to bolt and flower after you’re done harvesting heads.
• Plants produce tall stalks with small yellow flowers, followed by fluffy seed heads.
• When seed heads turn dry and fluffy, cut stalks and place them in a paper bag or over a tray.
• Rub the heads gently to release the small seeds and remove excess chaff.
• Store seeds in a labeled, airtight container in a cool, dry, dark place; lettuce seeds generally remain viable for several years.

Tips for Success

• Give iceberg rich soil, steady moisture, and cool temperatures for the best heads.
• Use transplants for spring crops in areas with short, unpredictable springs, so heads mature before hot weather.
• Mulch and consistent watering help prevent tip burn and bitterness.
• Grow near the kitchen door or in raised beds so you can harvest crisp, cold heads at peak freshness.

Note: Growing conditions and timing vary by region. Adjust sowing dates, watering, and heat or frost protection to match your local climate and weather patterns.