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Lettuce Growing and Harvest Information

by chuck.mcmullan

Where to grow Lettuce

Lettuce can be grown practically anywhere. Lettuce is a cool-season vegetable, with an ideal temperature of 50-60 degrees. It does poorly in hot weather and is tolerant to some frost and light freezes. The leafy types mature quickly and are more suited for warm climates. Cos is also more heat tolerant. It will prefer a little shade during the warmer part of the season. It can be grown year-round with proper varieties, and some additional winter protection. Lettuce will generally grow best in the spring and fall seasons.

Recommended Varieties of Lettuce

There are two basic categories of lettuce: heading and non-heading. Head lettuces include crisphead (e.g. Iceberg) and butterhead (e.g. Bibb and Boston). Non-head lettuces include leaf and romaine (also known as cos). Head lettuces tend to be milder in flavor but are more difficult to grow.

Recommended varieties:
Head – Fulton; Ithaca; Big Boston.
Bibb – Buttercrunch; Summer Bibb.
Leaf – Black Seeded Simpson; Salad Bowl; Ruby; Oak Leaf; Slobolt; Grand Rapids.
Cos or Romaine – Parris Island.

For a heat tolerant alternative try: Amaranth

Soil for Lettuce

Lettuce doesn’t do well in very acidic soils, and some say the pH shouldn’t be lower than 6.5. A rich, muck “celery” soil is excellent for lettuce, but the crop will also do well in average garden soil. The best crops are grown in soil that is deeply enriched with well-rotted manure and is well-fertilized before planting, especially with high nitrogen (leaf-stimulating) fertilizers such as 10-8-4, cottonseed meal, or blood meal.

Planting Lettuce

When –

Early spring in regions where summers are hot, and again in late summer for a fall crop. Head lettuce, especially, requires a long, cool growing season, and seed is usually started 6 weeks ahead. Transplants can be purchased. When sowing leaf lettuce, rows can be made by mixing several varieties. As the crop wanes, a second sowing can be made, or else it can wait until late summer, for fall. During hot weather, sow lettuce in partial shade, as it doesn’t do well in the heat, and use heat-resistant varieties.

How –

Seed should be sown thinly in rows 1 foot apart; for leaf types, thin plants to 2-3 inches apart, then thin again by pulling every other plant when half-grown. This will encourage thickly developed plants. For head, Bibb, and cos types, space rows 18 inches apart, plants 8-10 inches apart. Closer spacing results in smaller heads, which may be preferable for small families. Specialty growers are spacing lettuce very close for selling baby lettuces, a rapidly growing produce market.

Germination40 - 80 F
For growth60 - 65 F
Soil and Water
FertilizerHeavy feeder, use compost.
Side-dressingApply balanced fertilizer
pH6.0 - 7.5
Seed Planting Depth1/4 - 1/2"
Root Depth18 - 36", taproot to 5'
Height6 - 12"
Width6 - 12"
Space between plants
In Beds - Head10 - 12"
In Beds - Leaf6 - 8"
In Beds - Romaine10"
In Rows12 - 14"
Space Between Rows14"
Average plants per person10 - 12
For leaf lettuce, start picking the leaves when there is at least 5-6 mature leaves of usable size. Usable size means about 2" long for baby lettuce, and 5-6" long for more mature lettuce. Keep picking until a seed stalk appears or the leaves become bitter. For head lettuce, when the head feels firm and mature, simply cut it off at the soil surface. Harvest all lettuce in early morning for the maximum carotene and best taste. Refrigerate immediately.
First Seed Starting Date: 25-46 days before last frost date
Last Seed Starting Date (head lettuce): 92-127 Days before first frost date
Last Seed Starting Date (leaf lettuce): 77 - 97 Days before first frost date
Last Seed Starting Date (romaine lettuce): 87 - 112 Days before first frost date
Companionsbeets (to head lettuce); all brassicas (except broccoli), carrot, cucumber, onion family, pole lima bean, strawberry
IncompatiblesNothing conclusive

How Lettuce Grows

Lettuce is about 95 percent water. It develops rapidly if the growing season is cool and moist. Head lettuce forms a tight, compact cabbage head from a dense rosette of leaves. Bibb develops a loose head of broad succulent leaves with superb flavor. Leaf lettuce has loose crispy or curly leaves that develop from a basal growing point. Cos and romaine also develop from a basal growing point, but the leaves are oblong and grow upright.

Cultivating Lettuce

Since cultivation is difficult with these shallow-rooted plants, a mulch of grass clippings, salt hay, clean straw, or the like, will keep the weeds out and the soil moist and cool. Watering is essential if rainfall is scant. The plants need almost constantly moist ground.

Storage Requirements
Lettuce does not store well for long periods and is best eaten fresh.
TemperatureHumidityStorage Life
32 F98 - 100%2 - 3 weeks
32 - 40F80 -90%1 month

Harvesting Lettuce

Head – 2 months. Pull the entire plant from the soil.
Bibb – 6-8 weeks. Pull the entire plant from the soil.
Leaf – 6 weeks and continually, since these are “cut and come again” plants. Cut the outer leaves when mature to allow center leaves to develop.
Cos – 2 months. Pull the entire plant.

To store lettuce and other greens, rinse well in cold water, spin them dry, and then store in a cloth bag.

Lettuce Pests

Aphids – Either grow nasturtiums near the lettuce, or if there is a heavy population use rotenone or pyrethrum. Most minor infestations can simply be washed off before the plants are eaten.
Slugs – Place beer in shallow pans at dusk and empty the drowned slugs as they feed and they will “dissolve.”

Lettuce Diseases

Most of the blights and troubles have been eliminated through plant breeding and hybrid vigor.

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