Cultural Tips for Growing Lettuce
In This Guide
Plant your garden in a convenient location, where you can check it frequently. Choose an area near an abundant supply of water so you can water as needed easily. Vegetables do best if they receive full sunlight (at least 4 to 6 hours a day). Plant them in a well-exposed area in the garden, where they are not shaded by trees, fences, or walls. Try to plant away from areas that will be watered by lawn sprinklers.
Whenever possible, select a location that is not heavily infested with weeds, especially weeds such as field bindweed, nutsedge, and Bermudagrass that can be hard to control with hand weeding. Also avoid areas that have had previous disease problems.
Try to plant on level ground. Level ground is easier to work on than sloping ground. Vegetables will do well on a wide range of soils; they do best in well-drained soils. If your soil forms a clump when squeezed, then it is too wet; if the soil crumbles easily, it is a good soil to use. Damp soil surfaces encourage snails, slugs, sowbugs, and root diseases; fruit decay and leaf spot diseases may also increase. Soil amendments can make clay and sandy soils easier to work with, and correct soil preparation can improve poor soil.
Adding organic matter (compost, peat moss, manure, sawdust, ground bark) makes clay and sandy soils easier to work with. The soil should be kept at a pH level of 6.0 to 6.5. Lime or gypsum can be added to soils low in calcium.
Choose silt loams and sandy soils or highly amended soil if of another texture. Lettuce does not tolerate soil salinity.
Any type of soil can be improved with soil amendments. Heavy clay or sandy soils can be improved by adding organic material such as compost, manure, or leaf mold. Texture is an important consideration when choosing an amendment. An amendment that is granular and fine grained is important for container mixes. For gardens, a more coarse-grained amendment can improve drainage and aeration. Work amendments into soil by rototilling, raking, or double-digging.
The preparation of your soil is just as important as adding fertilizer and soil amendments. Before working the soil, make sure it is moist but not thoroughly wet.
- Use a shovel, rototiller, metal bow rake, or all of them together to loosen the top 1 to 2 inches of soil. Rake the area to remove weeds and old crop debris. Be sure to dig out roots.
- Irrigate the plot deeply to encourage the germination of weed seeds.
- In a week or two, after a substantial number of weeds have germinated, work the area again to kill the weed seedlings. Be sure to break up the clods in the soil, as seeds planted in cloddy soil will germinate poorly and won't live long because the soil dries too quickly.
- Form soil into beds if desired, and plant while soil is still wet.
Time to plant
Lettuce includes head lettuce and loose-leaf lettuce. They are ideally suited to many parts of California. They are hardy, cool-season vegetables. Ideally, they are best grown when the average air temperatures are between 73° F during the day and 45° F at night. The growing season can be extended by using a floating row cover, which offers a few degrees of frost protection and provides a warmer growing environment. At higher temperature ranges, lettuce may bolt and become bitter. Loose, fluffy heads and tipburn may also be caused by high temperatures. At temperatures near freezing, young plants are not damaged, but growth is slow. Optimum temperatures for germination range from 68° to 77° F. Above 86° F, seed germination is inhibited.
|Planting Dates for Lettuce in California*
|North and North Coast
Monterey County north
|February – August
San Luis Obispo County south
|August – April
Sacramento, San Joaquin valleys
November – March
Imperial and Coachella valleys
|September – December
|*Transplants may be started indoors 4 to 6 weeks before the last frost date. Planting dates are only approximate as the climate may vary greatly within the regions denoted. Contact your local UC Master Gardener program and experiment on your own to find more precise dates.
Lettuce is suitable for a small garden if compact varieties are grown. In suitable climates, it can be planted more than once a year for a continuous harvest. Lettuce can be seeded directly or transplanted into the garden. It is best planted on raised beds made by adding large amounts of soil amendments so that a bed is established above the previous level of soil.
If seeding, plant more seeds than necessary so as to make up for any losses. Plant seeds in rows 2 feet apart. Push them into the soil 0.25 inch deep or less. Fill these holes by scratching the surface, firm the soil lightly, and cover with a thin mulch of organic material in order to hold soil moisture. Keep moist during the germination period. If growing lettuce during the summer months, protect seedlings from sunburn with 50% shade cloth or two layers of floating row cover until they have about six leaves. Lettuce plants should be thinned anywhere from 3 to 8 weeks after plants reach the three- to four-leaf stage. Thin to 6 inches between plants for leaf lettuce and to 12 inches for head lettuce.
For transplants, use young plants with four to six true leaves, wider than tall, stocky, succulent, and slightly hardened to outdoor conditions. Spread and mix organic amendments and a good granular phosphorus fertilizer over the area. Mark where you want each plant and make the hole deep enough to bury the stem as far as the first leaf. Place the plant deep into the hole. Head lettuce should be spaced 12 inches apart; leaf lettuce 6 inches apart with 2 feet between rows. Press the soil firmly around the plant and water thoroughly to remove any air pockets. If transplanting in the summer, shade the plants in the middle of the day for the first week or use floating row cover.
Most vegetables require fertilizer for growth. Organic materials, such as manures and compost, and inorganic materials, such as chemicals, can be used to fertilize plants. Using both types of materials usually provides the best growth. Manures and compost can be used to increase soil fertility. They are usually applied at 1 pound per 4 or 5 square feet. These materials should be worked into the soil several weeks before planting in order to allow it to decompose. Manure that contains straw, sawdust, or similar materials should be applied with a commercial nitrogen fertilizer. Generally, if the soil has been properly amended with compost or manures or other organic materials, the only nutrient needed is nitrogen, if anything. Some commercial nitrogen fertilizers available are urea, ammonium sulfate, calcium nitrate, and ammonium nitrate. Apply these fertilizers at rates of 0.5 to 1 pound of nitrogen per 100 feet of row.
If manure and other organic material has not been used, apply fertilizer that contains both nitrogen and phosphorus before planting. All commercial fertilizers are labeled by the percentages of N-P-K; nitrogen (N), phosphorus (P), and potassium (K). Some common mixed fertilizers are 5-10-5, 5-10-10, 8-16-16, and 12-12-12. Apply these fertilizers at rates of 1 - 2 pounds per 100 feet of row. After plants are 3 to 4 inches tall, sidedress nitrogen in narrow bands or furrows and water thoroughly after application, or apply through the drip system. Consider light but frequent applications of nitrogen fertilizer every 3 to 4 weeks. Avoid letting the fertilizer come into contact with the plant stems to avoid burning.
Inorganic fertilizers can be sidedressed. Manures are more difficult to use as a side dressing and must be tilled into the soil.
Banding: Make a small groove 1 or 2 inches deep on both shoulders of the bed, 4 to 6 inches from the plant row and band in the fertilizer. Replace the soil and irrigate.
Broadcasting: Fertilizers can be scattered along the bed shoulders. Work into the soil soon after. This is less efficient than the banding method but will be more practical when the plants are so large that the bed shoulders are inaccessible for banding.
Where sprinklers are used, fertilizer may be scattered on the soil surface between rows before irrigating. Where drip or trickle tubes are used, apply fertilizer on the soil surface near the drip tube.
Lettuce can be grown under drip, sprinkler, or furrow irrigation. Examine your soil visually and with your hands to determine the need for additional water. Water deeply by drip, furrow, or overhead irrigation to encourage deep rooting. Avoid wetting foliage with overhead watering. If you allow water to seep through only to the top few inches of your soil, root growth will be stunted. Keep adequate moisture in the deeper soil layers even when plants are small. Deep moisture is harder to replace later in the growing season without over irrigating.
Proper irrigation will keep your plants vigorous and help protect them from thrips damage.
Harvesting and Storing Lettuce
It may only take as few as 60 or 70 days for lettuce to mature depending upon the variety and temperature. Head lettuce crops should be harvested as soon as they reach maturity. Leaving them in the garden too long may result in bolting, sunburn, or possibly damage from freezing. Leaf lettuce can be harvested either all at once or over a long period of time by breaking off the outside leaves and allowing the interior leaves to continue to develop. Lettuce has a fairly short shelf life and it should be refrigerated as soon after harvest as possible.
Head of butter lettuce.
Seed bed preparation.
Amending soil to prepare for planting.
Bag of fertilizer.
Irrigation shut off valve.