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  MG Manual Reference
Ch. 10, pp. 100 - 103

[Selected Crops: intro | asparagus | beans | broccoli | brussels sprouts | cabbage | cauliflower | sweet corn | cucumbers | eggplant | lettuce | melons | onions | peppers | potatoes | squash | tomatoes | herbs | herb use ]


1 Leaf
2 Bibb
3 Crisphead
4 Cos/Romaine

Light: Sunny, tolerates shade; prefers shade where summers are hot.
Soil: Well-drained, loose loam.
Fertility: Rich.
pH: 6.0 to 7.0
Temp: Cool (60 to 70° F).
Moisture: Moist, but not waterlogged; frequent, light waterings.
Planting: Seed leaf or butterhead types as soon as soil can be worked in the spring, or in late summer. Crisphead and cos types may be transplanted in early spring or fall. Start seeds indoors 5 to 7 weeks prior to this date.
Spacing: 4 to 10 inches by 12 to 24 inches for leaf, cos, or butterhead. 12 to 15 inches by 18 to 30 inches for Crisphead.
Hardiness: Hardy perennial, should be mulched in autumn in areas of Arizona where the soil freezes.
Fertilizer Needs: Medium-heavy feeder, use starter solution on transplants, sidedress if nutrient deficiencies are noted.

Lettuce, a cool-season vegetable crop, is one of the easiest to grow. Lettuce withstands light frost; however, sunlight and high summer temperatures usually cause seedstalk formation (bolting) and bitter flavor. Slow-bolting or heat-resistant varieties are available and are recommended for extending the lettuce-growing season. There are several types of lettuce commonly grown in gardens.
Crisphead, also known as iceberg, is the lettuce most widely available as a fresh market type. It has a tightly compacted head with crisp, light green leaves. Many gardeners find this type difficult to grow because it requires a long season and some of the most advertised varieties are not heat-resistant and tend to go to seed as soon as temperatures go up. Select a slow-bolting variety and start seed indoors in late winter or late summer for best results. Transplant in early spring or fall to take advantage of cool weather and mulch well to keep soil temperatures from fluctuating and to hold moisture in. An organic mulch is more suitable than black plastic after soil warms up. Mulching also keeps soil off the leaves, reducing chances of disease from soil-borne organisms.
Butterhead, or Bibb lettuce, is a loose-heading type with dark green leaves that are somewhat thicker than those of iceberg lettuce. Butterheads develop a light yellow, buttery appearance and are very attractive in salads. A miniature variety of butterhead, Tom Thumb, is very easy to grow, requiring a short growing time. One head of this lettuce is about right for one or two services, so this is one lettuce to plant in succession, about two weeks apart. It may be started indoors for an even longer season. Bibb lettuce will develop bitterness readily if temperatures get too high.
Romaine, or Cos, is less commonly grown by gardeners, but is a very nutritious lettuce that deserves attention. It, too, is relatively easy to grow, forming upright heads with rather wavy, attractive leaves.
Most gardeners who grow lettuce raise the leaf type, either with green or reddish leaves. This type is fast-growing, long-lasting lettuce used for salads, sandwiches, and in wilted lettuce salads. Leaf lettuce basically needs only to be planted and harvested.
Sow leaf varieties in rows, 10-20 seeds per foot, in rows 8-12" apart. Thin individual plants 4-8" apart, depending on variety. Leaf lettuce also grows very successfully in a wide bed arrangement; seedlings are thinned to 4-8" on all sides. Cos and head types should be sown or transplanted 12-18" apart. If in rows, allow 30" between rows.
Cultivate carefully as lettuce is shallow-rooted. Use frequent, light waterings to encourage rapid growth, but do not over water, as this may cause disease of roots or leaves. Overhead watering should always be done in the morning to give plants time to dry off. As mentioned above, mulches are helpful in maintaining soil moisture and keeping leaves off the ground.
Lettuce planted in very early spring should be given full sun so that the soil will warm enough for rapid growth. For long-season lettuces, plant so that crops such as sweet corn, staked tomatoes, pole beans or deciduous trees will shade the lettuce during the hottest part of the day when temperatures are over 70º. Inter-planting, i.e., planting between rows or within the row of later-maturing crops like tomatoes, broccoli, and Brussels sprouts, is a space-saving practice. Some lettuces, like Tom Thumb and leaf lettuces, are attractive in flower borders.
Lettuce is best planted in succession, or using different varieties that mature at different times. Thirty heads of iceberg lettuce harvested at once can present a major storage problem! Leaf and Bibb lettuces do well in hotbeds or greenhouses during the winter and in cold frames in spring and late fall.
Diseases: Stem, leaf, and root rots, mosaic virus, big vein, lettuce drop, downy mildew, bottom rot.
Insects: Aphids, root aphids, whitefly, cabbagelooper, beet armyworm, leafminer.
Cultural: Tip burn from irregular moisture, or lack of calcium; bolting, bitterness due to high temperature or lack of moisture; leaf rots due to soil and/or water on leaves.
Days to Maturity: 40 to 80 days, depending on type.
Harvest: Leaf lettuce can be used as soon as plants are 5 to 6 inches tall. Use the older, outer leaves which contain high levels of calcium first. You may wish to harvest every other one of the largest plants to accomplish thinning.
Bibb lettuce is matured when the leaves begin to cup inward to form a loose head. The heads will never become compact. Cos or Romaine is ready to use when the leaves have elongated and overlapped to form a fairly tight head about four inches wide at the base and 6 to 8 inches tall. Crisphead is matured when leaves overlap to form a head similar to those available in groceries; heads will be compact and firm.
Crisphead lettuce will keep about two weeks in the refrigerator. Leaf and Bibb will store as long as four weeks if the leaves are dry when bagged. If lettuce is to be stored, harvest when dry, remove outer leaves but do not wash, place in a plastic bag and store in the crisper drawer.
Approximate yields: 5 to 10 pounds per 10-foot row.
Amount to Raise: 5 to 10 pounds per person.
Storage: Cool (32° F), moist (95% relative humidity) conditions for 2 to 3 weeks.
Preservation: Cool, moist refrigeration; canning and freezing not recommended.

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