How to grow Lettuce?

Lettuce is almost synonymous with salad. It is easily the most popular salad ingredient, as countless restaurant salads consisting of a bowl of lettuce with a couple of Cherry Tomatoes will testify. The lettuce available in supermarkets rarely measures up to those you can grow yourself. Lettuce is easy to grow if you give it the right conditions, which means fairly cool weather. The challenge comes in getting it to grow when you want it, rather than when it wants to grow. Lettuce is an ideal vegetable to grow as a beginning gardener or if you have kids who want to garden.

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Lettuce History

Lettuce probably originated somewhere around the Mediterranean or Near East and has been grown since the time of the ancient Egyptians.

Soil Preference

PH (min/max): 6.0 - 7.5
PH Ideal (min/max): 6.8 - 7.0

Lettuce needs to grow fast for best quality, which requires a good soil. It should be fertile, moisture retentive, well drained and rich in organic matter. The pH isn't particularly important. Light soils that warm up quickly are good for early lettuce.

How to care for Lettuce?

Lettuce needs to grow quickly for best quality. This can only be done by giving the plants everything they need.

Lettuce is largely composed of water and it responds to irrigation by giving a larger and better tasting harvest. If you think the plants might need water they probably do.

Lettuce has a weak root system and isn't a very efficient feeder, so the soil needs to be quite fertile. Its main requirement is for nitrogen, but it also needs moderate amounts of potassium and phosphorus.

Seed Viability: 2-5 Years

Germination Percentage: 80.0

It is fairly easy to save lettuce seed. The plants are mostly self-pollinated, though there may be some cross-pollination from insects. It is recommended that varieties be separated by 25 feet to keep them pure, which is simple enough. If you save the seed from your best plants, you can develop better strains than you can buy (and have higher quality seed). You can save lettuce seed with no thought for purity if you don't care if the variety is somewhat mixed up, as it will give you plenty of seed for growing cut-and-come-again lettuce. You can gather seed from plants that have bolted, but it is important not to gather it from the first plants to [bolt]. Early flowering is not a trait you want to perpetuate.

Head lettuce can present a problem when it comes to seed saving. The head may be so dense that the flower stalk may not be able to get out. If this is the case, you may have to cut an X in the top of the head, to enable the flower stem to emerge (as you would with a cabbage). If the flower stem is very big you may have to stake it, to prevent it from falling over when it gets loaded with seed.

The yellow flowers are followed, 2 to 3 weeks later, by fuzzy seed heads. Gather the seed as it ripens by holding a paper bag over the head and shaking. The seed ripens sequentially, so you must collect it every few days to get all the ripe seed. Keep on collecting until you have all the seed you need, or until it is blown away by the wind. Alternatively you can cut the entire head when about 50% of the seed has ripened and dry it in a paper grocery bag. Clean the seed as much as possible, then dry and store it in a cool place. Newly harvested seed usually won't germinate for a couple of months.

Lettuce Mosaic virus can be seed borne so watch out for it if you save your own seed, or swap seed with others.

Part shade

In hotter climates it doesn’t mind part shade (and may even benefit from it).

Conditions:Warm

Season:Short Season, Long Season

Sun: min. 6 hours daily

In cool climates Lettuce needs full sun.

Conditions:Cool

Season:Short Season, Long Season

Crisphead Lettuce has stiff, fleshy leaves and keeps very well, in fact that is why it is so popular with commercial growers. It will keep for several weeks in a plastic bag in a refrigerator. The other types are somewhere in between. Don’t wash Lettuce until you are going to use it.

Storage Req: Refrigerator
Storage Temp: 35-40°F
Storage Length: 1-14 days

Leaf lettuce has thin leaves and won’t keep for much more than a week.

Storage Req: Refrigerator
Storage Temp: 35-40°F
Storage Length: 1-7 days

Problems

Bitterness

This is a characteristic sign of imminent [bolting], but it may also be caused by water stress or unusually warm weather. Once it happens there isn't much you can do about it.

Vernalization

Lettuce will [bolt] if the plants are [vernalized] while small. This happens if a plant with a stem diameter greater than ¼˝ is exposed to temperatures below 50˚ F for two weeks. When the weather warms up it senses that winter has passed and so goes into flowering mode.

Snails and Slugs

These molluscs love the tender young leaves and are the commonest problem you will face when growing Lettuce.

Mammals

Deer, Rabbits and Groundhogs can quickly devastate even a mature Lettuce patch. A fence may be necessary if you have these problems.

Cutworms

These can be a real problem for young seedlings in spring. Some gardeners use individual Cutworm collars of cardboard. If you find plants laying on the ground, dig in the soil around them and you can usually locate the culprit. If you find it you can prevent it doing further damage.

Bolting

Lettuce flowers when the day length gets up to 14 or 16 hours (the exact day length depends upon the variety), even if the weather is cool. Warm weather (above 75 to 80˚ F) frequently accompanies the long days of midsummer and may hasten [bolting], but it isn’t the primary cause. Bolting will also occur when a plant reaches full size and has all the resources it needs to flower. When the plant has enough large leaves they signal the plant that it is ready to flower, so it may be possible to slow it down by the frequent picking of single leaves (this won’t stop it though).

When a plant starts to bolt, it turns bitter, the head elongates and the new leaves begin to take on an elongated shape. Then the flower stalk appears. Lettuce plants are quite beautiful at this stage and if left alone will soon produce an abundance of seed. If you allow them to produce seed, you'll have plenty available for growing cut and come again salad or Microgreens.

Tip Burn

Burnt looking leaf tips may indicate a shortage of calcium, or night temperatures over 65˚ F.

Lettuce Types

Batavian / French Crisp, Green

Batavian or Summer Crisp varieties form moderately dense heads with a crunchy texture, similar to a cross between iceberg and looseleaf types of lettuce.

Romaine / Cos, Red

Romaine varieties grow a long head of sturdy leaves with a firm rib down the center, and are quite popular in the United States. This is the variety of lettuce used in the popular Caesar salad. They are fairly easy to grow and tolerate some heat. Under good growing conditions, these varieties can be one of the fastest growing crops.

Looseleaf, Red

Looseleaf varieties have tender, delicate, and mildly flavored leaves. They generally do not form a head like other varieties and are usually harvested while the leaves are still small. They are fairly easy to grow and tolerate some heat. Under good growing conditions, these varieties can be one of the fastest growing crops.

Batavian / French Crisp, Red

Batavian or Summer Crisp varieties form moderately dense heads with a crunchy texture, similar to a cross between iceberg and looseleaf types of lettuce.

Butterhead / Boston / Bibb, Red

Butterhead / Boston / Bibb varieties have soft, loosely packed heads, very good flavor and buttery texture. They are fairly easy to grow and tolerate some heat. These varieties are quite popular in Europe, but have been increasing in popularity in the United States.

Butterhead / Boston / Bibb, Green

These varieties have soft, loosely packed heads and very good flavor. They are fairly easy to grow and tolerate some heat. Under good growing conditions, these varieties can be one of the fastest growing crops.

Heading / Iceberg / Crisphead

Iceberg or Crisphead varieties form tight, dense heads that resemble cabbage. They are the mildest in flavor, and generally grown for their crispy texture rather than for flavor.

Looseleaf, Green

Romaine / Cos, Green

Pests

Wireworm
Flea Beetle
Birds
Thrips
Mealybug
Leafhoppers
Aphids
Cutworms
Tarnished Plant Bug
Armyworms
Leafminers
Nematodes
Slugs and snails
Groundhog
Rabbits
Raccoons
Gophers
Deer

Diseases

Bacterial Spot
Fusarium Wilt
Damping Off
Downy Mildew
Powdery Mildew

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