Lettuce: sowing, caring for, and harvesting

Description and botany

Lettuce (Lactuca sativa) is an edible vegetable plant, cultivated as an annual, belonging to the vast and cosmopolitan Asteraceae family. This makes it a distant cousin of daisies, chrysanthemums and sunflowers!

Botanical illustration

Its exact origin is difficult to pinpoint, but it certainly derives from a wild form that grew naturally in Western Asia and the Near East, likely in the mountains of Kurdistan. What is certain is that it has been consumed since antiquity! The Romans and Greeks enjoyed it as an “appetiser” to line their stomach walls before indulging in gargantuan meals. They appreciated its leaves for their bitterness, as well as its soporific and anti-aphrodisiac properties. It was Roman farmers who, by crossbreeding species, developed a stemless plant with large edible leaves. Thus, romaine lettuce was born.

Later, in the Middle Ages, it was still consumed, as Lactuca sativa is mentioned in Charlemagne’s Capitulare de Villis. Its narcotic properties had by then disappeared. It was during the 17th and 18th centuries that lettuce became a staple on dining tables, mainly in its head-forming varieties. This rise was due to the practice of forcing, which extended the cultivation period. In the 19th century, with the expansion of large-scale market gardening areas, lettuce became one of the most common leafy vegetables on market stalls. This remains largely true today, thanks to the ease of growing lettuces under glass.

Etymologically, the term “lettuce” comes from the Latin word “lacta“, meaning “milk”. Indeed, the stems of the wild ancestor of our lettuce contained a white juice resembling milk.

Today’s commercially available lettuces fall into several categories:

• Butterhead lettuce (Lactuca sativa var. capitata) (commonly called lettuce) with smooth or crinkled leaves, tightly packed around a heart, green or red
• Batavia lettuce with lobed, undulate, sometimes frilly leaves that are both tender and crisp with their palmate veins
• Romaine lettuce (Lactuca sativa var. longifolia) with thick, crisp leaves and stiff midribs, forming an upright elongated head
• Cutting lettuce (Lactuca sativa var. crispa) with foliage that regrows after cutting. These lettuces don’t form heads
• Iceberg lettuce with thick, crinkled leaves forming a small head

We could also add Italian lettuces, often red in colour, with more or less crisp leaves. They’re often classified as cutting lettuces as they don’t form heads. The stem lettuce (Lactuca sativa var. augustana), also called celtuce or asparagus lettuce, is mainly eaten cooked in Asia. It’s grown for its swollen stem and leaves that don’t form a head.

Lettuces are therefore annual vegetable plants with an upright habit, broad leaves and short stems. They first form rosettes of entire leaves. Then comes the heading phase which distinguishes the different types of lettuce. This is the stage used for consumption. Afterwards comes the reproductive phase for seed harvesting.

The leaves are glabrous, without prickles or spinulose cilia, soft and ovate. The lower leaves are most often divided while the middle and upper leaves are more ovate and dentate, embracing the stem from the base.

As it belongs to the Asteraceae family, lettuce flowers as small heads comprising 12 to 20 yellow ligulate florets, closed at ripeness. They are grouped in corymbiform panicles. From June to September, these flowers appear on long upright stalks after the head elongates into small clusters. This running to seed, characterised by stem elongation and flowering, is encouraged by heat. These flowers produce downy greyish or whitish achenes.

Depending on the variety, some lettuces are classified as spring lettuces (to sow outdoors from June to November) or summer lettuces (to sow outdoors from May to August), or winter lettuces (to sow outdoors from August to November).

Lettuces are sensitive to temperatures that are too cold or too high, which is why it has become common to grow them under cloches or in greenhouses.

The best lettuce varieties

Butterhead Lettuces

Crisphead (Batavia) Lettuces

Cos (Romaine) Lettuces

Cut-and-Come-Again Lettuces

Summer Crisp (Grasses) Lettuces

Butterhead Lettuce Marvel of Four Seasons

This lettuce produces large heads of green leaves broadly tinged with red. It can be sown from February to July

• Height at maturity 25 cm

See the product sheet

Butterhead Lettuce Reine de Mai - Lactuca sativa

This heritage variety of lettuce forms medium-sized heads of pale green leaves delicately flushed with red. It's an early variety, ideal for spring and early summer cultivation

• Height at maturity 20 cm

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Lettuce Picholine - Lactuca sativa

This lettuce produces dense heads of deep red leaves, rather thick and glossy. It's easy to grow and highly disease-resistant

• Height at maturity 20 cm

See the product sheet

Batavia Lettuce de Pierre Bénite - Lactuca sativa

This Batavia lettuce forms beautiful heads of tender, crisp leaves, slightly curled and blistered, in a lovely light green. It's a vigorous variety that withstands heat well and doesn't bolt easily

• Height at maturity 25 cm

See the product sheet

Batavia Lettuce Rouge Grenobloise - Lactuca sativa

This Batavia lettuce produces handsome heads of dark green leaves edged with red. The leaves are thin yet crunchy. A very vigorous variety

• Height at maturity 20 cm

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Batavia Lettuce Reine des Glaces - Lactuca sativa

This iceberg-type Batavia forms heads of dentate leaves. It's cold-resistant and very crisp

• Height at maturity 20 cm

See the product sheet

Lactuca sativa 'Romaine Blonde Maraîchère'

This traditional Romaine lettuce variety offers thick, crisp leaves forming upright heads. Its heat resistance makes it ideal for summer and autumn harvests

• Height at maturity 25 cm

See the product sheet

Romaine Lettuce dHiver de Sainte Marthe - Ferme de Sainte Marthe seeds

This hardy Romaine lettuce variety should be sown from August to October for harvest the following spring. Its pale green foliage forms large, compact heads

• Height at maturity 20 cm

See the product sheet

Oak Leaf Lettuce Blonde à graine noire - Lactuca sativa

The essential cut-and-come-again lettuce with thick, broad leaves in green or red. Very easy to grow, resistant to heat and disease

• Height at maturity 20 cm

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Lettuce Lollo Rossa - Lactuca sativa

This cut-and-come-again lettuce variety has curly red leaves, very tender with a particularly pleasant flavour

• Height at maturity 30 cm

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Lettuce Grasse Sucrine - Lactuca sativa

This summer crisp lettuce variety has thick leaves with a slightly sweet flavour. It forms tight heads with an upright, vertical habit

• Height at maturity 25 cm

See the product sheet

Lettuce sowing

Lettuces are easy-to-sow salad plants. You can also easily purchase lettuces as plug plants or young plants in buckets that can be transplanted into the garden.

When to sow?

Depending on the time of year, lettuce sowing is done under cover (cold frame, tunnel or unheated greenhouse) in colder regions or directly in the ground.

Thus, so-called spring lettuces (‘Gotte jaune d’or’, ‘Reine de mai’, ‘Appia’) are sown from February or March under cover or directly in the ground in southern regions, but can be sown until July.

Summer lettuces (‘Grosse Blonde Paresseuse’, ‘Laitue du bon jardinier’, ‘Kinemontepas’, ‘Merveille des quatre saisons’) are sown directly in the ground from late March to August.

Finally, autumn lettuces (‘Verpia’) and winter lettuces (‘Merveille d’hiver’, ‘Trémont’, ‘Val d’orge’) should be sown directly in the ground in August and September. For these, it is advisable to provide protection such as a tunnel or winter fleece. Harvesting will take place in the first days of the following spring.

Butterhead and romaine lettuces are very heat-resistant. This is why they are sown from March to June. Lastly, cutting lettuces are sown in place from March to August, but care must be taken to water them as they bolt quickly in hot weather.

So, in summary, lettuces are sown from March to late September, to ensure staggered harvests throughout the year. It is best to sow during a waning moon.

Where to sow?

Lettuces adapt to all types of soil, except overly acidic or saline soils. However, the soil should be rich in organic matter, fairly moist and light, and above all well loosened, as lettuce has a shallow root system. Before sowing, it is therefore recommended to incorporate well-rotted compost or manure.

In terms of exposure, lettuce needs light and warmth to grow, but it dislikes scorching sun. This is why a semi-shaded spot with good light suits it well, especially in warmer regions. North of the Loire, a sunny location can be chosen for spring sowings.

How to sow?

Directly in the ground

• Draw furrows spaced 30 to 35 cm apart and half a centimetre deep
• Sow thinly, spacing the seeds
• Cover with a very light layer of soil to avoid burying the seeds too deeply
• Water with a fine spray

Subsequently, the soil should be kept moist. When the seedlings have 3 to 4 leaves, thin them out, keeping only one plant every 20 cm. However, cutting lettuces do not need thinning.

Under cover

• Fill your trays, seed pans or buckets with special sowing compost
• Sow thinly at a depth of 0.5 cm
• Cover with a very fine layer of compost
• Water with a fine spray

When the seedlings have 4 true leaves, they can be transplanted into the ground, spaced 20 to 25 cm apart in rows. Keep only the most vigorous ones and be careful not to bury the collar.

For more information, read Solenne’s article: Growing lettuces under cover (greenhouse, tunnel and cold frame)

To make sowing easier and avoid thinning, try seed tapes, which are practical and quick.

Lettuce Care

Lettuces are not difficult to care for. However, a few key practices are essential to promote their growth and, most importantly, prevent them from bolting during the hottest periods.

To aerate the soil, regular hoeing is important. These repeated hoeing sessions will also help keep the soil clean and free of weeds.

In case of prolonged intense heat, mulching is recommended to maintain a certain level of moisture. Indeed, lettuces dislike heat and drought. This is why it is advisable to water them regularly (especially during heatwaves) to keep the soil consistently cool. It is best to water lettuces at the base rather than with a sprinkler to avoid foliage diseases.

Early or late-season varieties may need protection from the cold by using a tunnel, frost cloth, or cloches.

Pests and Diseases of Lettuce

When it comes to pests, lettuce is a veritable feast! Depending on the season, numerous pests are drawn to its tender leaves. These pests can be particularly destructive, causing significant damage. First and foremost, aphids are present throughout the growing period. Various species of aphids should be eliminated before the lettuce forms heads. Black soap diluted in water is quite effective, as are fern manure or garlic manure.

Other pests that target lettuces include slugs and snails. To get rid of them, I recommend reading Ingrid B.’s article: 7 effective and natural ways to combat slugs.

Among lettuce pests, we also find defoliating and terricolous noctuids, whose caterpillars feast on tender leaves. They are dangerous from April until autumn. Again, fern and garlic manure are powerful repellents, but pheromone traps can also be used.

Finally, one last enemy lurks unseen in the soil, biding its time: the wireworm. It attacks the lettuce collar, severing it cleanly. It is active from April to October. Olivier explains how to eradicate them in his article: Wireworm: damage, treatment, and organic control.

In terms of diseases, lettuces are also vulnerable, especially if growing conditions are not ideal. In damp and cool weather, downy mildew (a white, farinose coating) can attack the leaves, as can botrytis, identifiable by red lesions on the collar. As for anthracnose, it thrives in high humidity and mild temperatures around 20°C.

Lastly, lettuce can be susceptible to sclerotinia, a disease caused by the fungus Sclerotinia. This disease leads to wilting, followed by a white coating and sclerotia—survival structures that can persist in the soil for up to seven years. To prevent this disease, it is crucial to remove crop debris, avoid overcrowding lettuce plants, and practice crop rotation. For treatment, horsetail decoction is effective.

→ Also read: Diseases and pests of lettuces

How to pair lettuce?

Lettuce is a good companion that can be paired with beetroot, cabbages, peas, radishes and strawberries.

Thanks to their rapid growth, lettuces can also be planted at the base of slower-growing vegetables such as courgettes, tomatoes, and peppers. These will provide the partial shade necessary for its development and the coolness from watering.

However, the principle of intercropping is not feasible with garlic and onions, which have completely different cultivation requirements.

Harvesting and Storing Lettuce

Lettuces should obviously be harvested before they go to seed, when the head is firm for romaine and butterhead varieties. Do not pull up the plant, but cut at the collar level, leaving the root in the soil. New shoots will quickly develop and can be eaten. Simply continue to water.

Cut-and-come-again lettuces, on the other hand, should be harvested as needed. Simply cut the leaves just above the collar with a knife. Again, remember to water to encourage new leaf growth.

Lettuces are best harvested in the morning. They should be eaten as soon as possible. They can be stored for 24 hours in the fridge’s vegetable drawer.

Uses and Nutritional Benefits

Lettuce contains over 95% water and few energy components, making it a low-calorie vegetable (around 15 Kcal/100g). However, it is rich in fibre, minerals (iron, manganese), vitamins A, K, B9 and C, and trace elements. It also has antioxidant properties.

Lettuce is mainly eaten in salads, with vinaigrette. To preserve all the benefits of this lettuce, it’s important to prepare it at the last minute by tearing the leaves by hand rather than cutting them with a knife. The leaves should be thoroughly dried. Lettuce leaves can also be added to sandwiches or stuffed with fresh cheese for appetisers. When cooked, lettuce can be braised, used in parcels, or added to soups.