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Lettuce Care At A Glance

Cool season, leafy green annuals with hundreds of different cultivars and selections.
Several distinct lettuce types are available with different characteristics and uses.
All prefer loose, well-drained organically rich soils with a pH of 6.0-7.0.
Plant in full sun.
Start seeds early, to get seedlings out prior to the onset of hot weather.

Planting Instructions

Start seeds indoors 6-8 weeks prior to the last average frost date.
Use pre-moistened seed starting mix firmed into trays, cell packs, or small pots.
Gently press lettuce seeds into the top of the mix with little to no cover. Small seeds benefit from light.
Thin seedlings to 4 inches apart for leaf lettuce types and 6-8 inches for Romaine or Butterhead types.
Lettuce seeds germinate best with consistent soil temperature of 65° to 70°F.
Keep the medium moist, not soggy. Cover with a plastic dome or kitchen wrap.
Once seeds germinate, remove from bottom heat, provide bright light, and 8°-10°F cooler room temperature.
Harden seedlings off for 7-10 days prior to planting out.
NOTE: Seedlings will be tender to frost until they are properly hardened off.

Direct Sowing Seeds

Direct sow Looseleaf, Romaine, or Butterhead varieties in early spring in soil with average moisture and good drainage.

NOTE: Avoid muddy or mucky soil conditions. Likewise, if soils are too dry, lettuce seeds will not germinate well.

Sow seeds in early spring, which is the optimal time to sow lettuce seeds in most climates. For fall crops, sow seeds around mid-August to September in most zones.

NOTE: Seedlings exposed to too many consecutively cool days of 40° to 50°F may cause bolting when temperatures do rise. Planting successive crops can help ensure some lettuce plants will mature properly without bolting.

Sow seeds in single, double, or triple rows that are 12 to 15 inches apart.
Seeds are small, therefore, require light for germination, do not cover deeply. Vermiculite works well as a cover.
Keep the soil consistently moist but not soggy.
Soil temperature of 60° to 70°F is optimal. In cooler soils, seeds can still germinate, it just takes longer, so be patient.
Once seedlings emerge, thin leaf lettuce types to 3-4 inches apart, and 6-8 inches apart for Romaine or Butterhead.

Types

Looseleaf

Well adapted to many climates. Plants form loosely arranged leaves around a central stem close to the ground with many different leaf colors and textures available including Mesclun types. Fastest maturing at only 40-50 days or less.

Romaine or Cos

Romaine types form upright, elongated heads of ruffled green leaves with firm center ribs. More heat tolerant than other lettuce types. Number of days to maturity varies by variety but are typically 50-70 days.

Crisphead or Iceberg

Dense round heads of cabbage-like leaves around a tight central core. Outer leaves are green with inner leaves of pale yellow to white. Leaves have high-water content, a crunchy texture, and a mildly sweet flavor. Iceberg lettuce is most sensitive to growing conditions, resenting heat, cold, drought, and excess moisture. For most climates, the optimal growing window is narrow, making these types most challenging for home gardeners to cultivate. Most are 70-90 days to maturity.

Butterhead or Bibb

Butterhead types are semi-heading, small to medium-sized with tender bright green loose leaves with a "buttery" flavor suitable for salads or sandwiches. Butterhead varieties are cut and come again types. Plants are adaptable to various growing conditions with most varieties maturing in about 60-70 days.

Watering

Lettuce plants develop quickly, so frequent and light waterings are best to match plant growth.
Since it is nearly impossible to keep lettuce foliage dry while watering, water in the morning shortly after sunrise to allow the longest time for leaf drying, which helps to avoid leaf burning and spotting diseases.
Overwatering is highly detrimental, often leading to unavoidable disease issues, especially in heavy clay or dense and compacted soils.

Fertilizing

Lettuces are considered heavy feeders. Adding appropriate amounts of granulated fertilizer 4 weeks prior to planting is beneficial, as well as periodic feedings during the growing season as needed.
Amend the soil prior to planting with an all-purpose 10-10-10 fertilizer at a rate of 3-5 pounds per 100 sq. ft. or use the same application rate for organic 3-5-3 or 5-3-3 food.
During the growing season, if plants are slow to recover after cutting, apply a naturally derived, water-soluble, vegetable-specific food with 4-6-7, 2-6-4, or 6-6-6 formulations, once every week after watering.

Troubleshooting

Bitter Tasting Leaves

Plant stress due to hot weather or drought conditions leads to bitter tasting lettuce.
Keep plants consistently watered, especially during periods of hot weather.
Plant early enough to get good harvests prior to the onset of summer's hottest temperatures.
The bolting process will lead to a bitter flavor.
Choose varieties that suggest they are "more heat tolerant" or "less bitter," such as 'Buttercrunch', 'Red Salad Bowl', or 'New Red Fire'.

Leaves with Tip Burn

Tip burn can be caused by several factors.
Inconsistent soil moisture - Water more consistently or try mulching around plants.
Hot temperatures can lead to leaf tip burn - Use grow tunnels or floating row covers to lessen sun intensity.
Lack of calcium can cause leaf tip burn - Nutrient imbalances can inhibit proper calcium uptake. Have a soil test done to determine nutrient levels and soil pH. Use those test results to make appropriate soil adjustments. Burnt or brown leaf tips can be trimmed off to still use the rest of the leaf.
Tip burn can be a symptom of fungal disease - Thin plants properly, rotate planting locations, limit overwatering, promote proper drainage, air circulation, and pH.
Tip burn can be caused by leaves staying too wet from rain or watering too long without drying - Water early in the day.

Bolting

Bolting is the physical transformation from the vegetative state (leaves) to the reproductive state (flower stalk formation).
Lettuce bolting is caused by a combination of day-length, temperatures, and plant maturity. Once bolting starts, it cannot be stopped.
Plant lettuce early and often up until temperatures get too warm. 55° to 65°F is the optimal temperature range for growing lettuce. Once temperatures get too warm, wait to start a fall crop in late summer.
Water consistently, mulch, and fertilize appropriately to keep plants as healthy as possible.