Planting Timeline
Showing dates for Iceberg in USDA Zone 7
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Iceberg · Zones 2–9
Growing Details
Zone-by-Zone Planting Calendar
| Zone | Indoor Start | Transplant | Direct Sow | Harvest |
|---|---|---|---|---|
| Zone 3 | March – April | May – June | — | July – September |
| Zone 4 | March – April | May – June | — | July – September |
| Zone 5 | February – August | April – September | — | June – October |
| Zone 6 | February – August | April – September | — | June – October |
| Zone 7 | February – September | March – October | — | May – November |
| Zone 8 | January – October | March – November | — | May – December |
| Zone 9 | September – February | October – March | — | December – May |
Complete Growing Guide
Growing perfect Iceberg lettuce heads requires mastering the art of cool-season timing and soil preparation. Start by choosing your planting window carefully — aim for soil temperatures between 45-65°F, which typically means early spring planting in zones 3-6 and fall/winter growing in zones 7-10.
Prepare your soil with 2-3 inches of compost worked 8 inches deep, ensuring excellent drainage while maintaining moisture retention. Iceberg demands consistent soil moisture but will rot in waterlogged conditions. Test your soil pH and adjust to 6.0-7.0 for optimal nutrient uptake.
Start seeds indoors 6-8 weeks before your last frost date, sowing in cell trays with quality seed-starting mix. Keep soil temperature at 60-65°F for germination, then move seedlings to a cooler 50-55°F environment once they emerge. This temperature drop is crucial for preventing early bolting. Transplant when seedlings have 4-6 true leaves and nighttime temperatures consistently stay above 32°F.
Space transplants 12-15 inches apart in rows 18 inches apart — overcrowding prevents proper head formation. Apply a balanced fertilizer (10-10-10) at transplanting, then side-dress with nitrogen-rich fertilizer every 3 weeks until heads begin forming. Avoid high-nitrogen feeding late in development as this promotes loose, leafy growth rather than tight heads.
Maintain consistent soil moisture with 1-1.5 inches weekly, using drip irrigation or soaker hoses to keep leaves dry and prevent disease. Mulch around plants with straw or grass clippings to regulate soil temperature and retain moisture.
Common mistakes include planting too early (leading to bolting), inconsistent watering (causing tipburn), and harvesting too late (resulting in bitter flavor). Watch for the first signs of bolting — a slightly pointed head top or visible flower stalk — and harvest immediately.
Harvesting
Harvest Iceberg when heads feel firm and solid when gently squeezed, typically measuring 6-8 inches across. The outer leaves should be tightly wrapped around the head with no loose, floppy appearance. Perform the 'squeeze test' — a ready head will feel dense and compact, similar to a softball's firmness.
Harvest in early morning when leaves are crisp and full of moisture. Cut the head at soil level with a sharp knife, leaving the root system intact. If you notice the head beginning to elongate or develop a pointed top, harvest immediately as the plant is starting to bolt and flavor will quickly turn bitter.
Avoid harvesting during hot afternoons when leaves may be wilted from heat stress. A properly timed Iceberg head will produce that signature 'crack' sound when you break apart the leaves — this indicates peak crispness and optimal harvest timing.
Storage & Preservation
Fresh Iceberg heads store exceptionally well when handled properly. Remove any damaged outer leaves and wrap the head loosely in paper towels, then place in a perforated plastic bag in your refrigerator's crisper drawer. Maintain humidity around 95% and temperature between 32-34°F for maximum shelf life of 2-3 weeks.
Unlike other lettuce varieties, Iceberg's dense structure makes it unsuitable for traditional preservation methods like dehydrating or freezing, as these destroy its signature crisp texture. However, you can blanch and freeze chopped Iceberg for use in cooked dishes like stir-fries or soups, though it will lose its crunch.
For extended freshness, core the lettuce and rinse the hollow core area with cold water every few days, wrapping again in fresh paper towels. This prevents the core from browning and maintains overall head quality.
History & Origin
Iceberg lettuce emerged in the late 1800s as American seed companies sought to develop a crisp head lettuce that could withstand long-distance shipping. The variety gets its name from early shipping practices when whole train cars of this lettuce were packed in crushed ice for transport from California's Salinas Valley to East Coast markets.
The modern Iceberg was perfected in the 1920s by California growers who selected for tight head formation, shipping durability, and that distinctive crisp texture. It became synonymous with American salad culture throughout the mid-20th century, dominating restaurant and home kitchens.
While food trends have shifted toward more nutritionally dense lettuce varieties in recent decades, Iceberg remains the gold standard for texture and storage life. Its development represented a breakthrough in agricultural logistics, enabling fresh lettuce to become a year-round staple across America rather than a seasonal, local crop.
Advantages
- +Exceptional storage life of 2-3 weeks when properly refrigerated
- +Unmatched crisp texture that holds up to heavy dressings and hot sandwich fillings
- +Heads maintain quality and don't wilt quickly at room temperature during meal prep
- +Dense head structure provides excellent yield per plant compared to leaf lettuces
- +Clean, mild flavor appeals to all palates and doesn't overpower other ingredients
- +Sturdy leaves perfect for lettuce wraps and taco shells
- +Reliable head formation when growing conditions are properly managed
Considerations
- -Highly sensitive to temperature fluctuations and prone to bolting in heat
- -Requires precise timing and cool conditions that limit growing seasons
- -Susceptible to tipburn when calcium uptake is disrupted by inconsistent watering
- -Long maturation period of 80-95 days ties up garden space
- -Lower nutritional density compared to darker leafy greens
Companion Plants
Plant Together
Chives
Repels aphids and improves lettuce growth and flavor
Carrots
Loosens soil for lettuce roots and doesn't compete for space
Radishes
Breaks up soil, deters flea beetles, and matures quickly between lettuce plantings
Marigolds
Repels nematodes, aphids, and other pests that damage lettuce
Nasturtiums
Acts as trap crop for aphids and cucumber beetles
Spinach
Similar growing requirements and can be interplanted for succession harvests
Garlic
Deters aphids, slugs, and rabbits that commonly attack lettuce
Dill
Attracts beneficial insects that prey on lettuce pests
Keep Apart
Broccoli
Competes heavily for nutrients and can shade out lettuce
Sunflowers
Allelopathic compounds inhibit lettuce germination and growth
Tomatoes
Large root system competes for nutrients and water needed by shallow-rooted lettuce
Pests & Disease Resistance
Resistance
Susceptible to tipburn and bottom rot, requires cool conditions to prevent bolting
Common Pests
Aphids, cutworms, wireworms, flea beetles
Diseases
Tipburn, bottom rot, downy mildew, premature bolting in heat