Lettuce [ Lactuca sativa ], is an annual plant that belongs to the asteraceae family. This family includes many garden flowers such as the calendula and sunflower. Lettuce is usually grown for it’s tender leaves, most often used in salads. The wild lettuce, the ancestor of our garden lettuce can be found in many countries across the globe and was brought to our shores by the Romans.
There are 7 main types of lettuce, Batavian, Buttercrunch, Butterhead, Chinese, Cos, Crisphead and Looseleaf. Within these 7 types are hundreds of varieties that come in a wide range of greens, reds and speckled. By selecting from the large selection of varieties available, lettuce can be grown and harvested almost year round.
Not widely grown in Britain, Batavian lettuce are also known as Summer Crisp lettuce and have thick crunchy leaves that do well in summer heat. They are greedy feeders and can grow quite large. Varieties include, the green leaved Nevada, and the red speckled Mottistone.
This lettuce looks similar to the Cos or Romaine lettuce and is a cross between Romaine and Butterhead varieties. The Buttercrunch lettuce has an upright growth habit with deep green crisp leaves that grow in a rosette. They are more resistant to leaf rot in wet weather than Butterheads. Varieties include, Buttercrunch and Winter Density.
Butterhead lettuce form loose open heads of tender almost soft leaves. It was one of the most popular lettuces available in greengrocers and supermarkets for many years until we started to favour more crisp lettuce. Butterheads are available in wide range of colour, tastes and sizes. Green varieties include Santoro and All Year Round, though despite it’s name is not frost hardy. Red varieties include Sierra and the red speckled green Flashy Butter Oak. A popular mini Butterhead, good for a small space is Tom Thumb, and for winter cultivation try Valdor.
These plants have very crisp, flavoursome leaves that are like a cross between a lettuce and a cabbage. It is often referred to as, Chinese Cabbage. It is grown mostly for use in stir-fries and soups, the variety Celtuce has leaves with a distinct celery flavour.
This is also called Romaine lettuce, these plants form slightly open upright heads with a good flavour and crunchy mid ribs. If given plenty of water, they can stand summer heat better than most other types of lettuce. The mini Cos lettuce Little Gem has become a British favorite and is widely available in shops. The Austrian heritage variety Speckled Trouts Back looks stunning in pots or in the veg bed with its bright green leaves speckled with red. A large deep green variety Lobjoits, is an old favorite on allotments. For Autumn sowing try Winter Gem.
These Crisphead or heading lettuce roll their leaves into a head very much like a cabbage. This lettuce has become know as the Iceburg lettuce and is the most popular lettuce sold in Britain. They are good in the garden too, they have good disease resistance and last well even in hot weather. There are many good varieties like the old favorite Webbs Wonderful, Saladin and Soleison are excellent choices. Red Iceburg had red tinged leaves for something different, and for pots or a small space, try Mini Green.
Looseleaf lettuce produce lots of leaves without growing a central heart, they are easy, grow fast and come in a wide range of colours and leaf shapes. You can grow individual plants, just pulling off leaves as you want them, or grow in rows or pots as baby leaves that you cut with scissors. You can often get a second cutting of leaves, this has led to them being called ‘Cut and Come Again’ lettuce. Varieties include Red and Green Salad Bowl, Red and Green Oak Leaf, the red Lolla Rosso and the green Lolla Bionda. Mixtures of looseleaf lettuce and mixtures that also include other types of salads leaves are also available.
Cultivation and Soil
Lettuce will grow in almost any soil but grows best in a moisture retentive soil. As lettuce is 80% water, never let it dry out. It will help if you can add some organic matter or compost to the bed. It also welcomes a little shade in high summer, so if you have a slightly shady spot that other veg doesn’t like, try some lettuce there. By choosing your varieties carefully and using some protection like a windowsill, greenhouse and cloches, you can have fresh lettuce for most of the year. With indoor sowings from January, and direct outdoor sowings from late March. You shouldn’t need to feed your lettuce plants, if you added lots of compost to the bed. If you do think they need a feed, try Comfrey or Seaweed, or Chicken pellets lightly forked in before planting.
Indoor sowings can begin from January onwards, as cold tolerance of the lettuces is good. Sow the lettuce seeds thinly into a pot or tray of moist multi purpose compost, cover lightly with sieved compost or vermiculite. Label and place into a propagator or on a warm windowsill to germinate. Once the seedlings are through, keep in bright light so they grow strong, not tall and spindly. When about 1-2 inches high, prick out individually into pots or modules and grow on undercover, protecting from cold and frost. If you are planning to plant your lettuce outside, then a couple of weeks before planting out, start to harden off the young plants. You can use a cold greenhouse, coldframe or cloche, or put your trays of plants outside during the day, remembering to bring in at night. Remember don’t sow too many seeds at a time. I often sow 2 or 3 varieties into a half seed tray, separating them with pieces of cane. Remember to label the different varieties.
When to plant out will depend on your local weather conditions, there is no point in planting out until the soil starts to warm up, but usually it will be around late March or April. You can plant out under cloches or layers of fleece, or use just use fleece as an overnight protection if the weather turns cold. Alternatively plant out in a greenhouse or polytunnel bed. Plant out the young plants according to the spacings on the seed packets. Planting distances will vary with the variety, but small compact lettuce can be spaced about 5-6 inches apart, while large crisphead varieties will need about 10 inches between plants. Chinese lettuces will need around 12 inches. You can as I often do, plant much closer, then harvest alternate lettuce plants for an early tender crop, allowing the others room to fully develop.
Direct Sowing Outdoors
Your local weather conditions will determine when you can start your outdoor sowings, in most places it will be about mid March onwards. Work the soil to a fine tilth, covering the area with a cloche or fleece for a few weeks can help to warm up the soil. Sow thinly in a shallow drill covering with about a half inch of fine soil. When the seedlings are about 2 inches high, thin out to 3-4 inches apart. In a few weeks the lettuce seedlings can be thinned again to their final spacings. The best way to keep cropping lettuce, is to sow a short row [ about 4 ft ] every 2-3 weeks. This will give a succession of lettuces throughout the season.
Sowing Baby Salads or Cut and Come Again
Any lettuce can be used for baby salad or cut and come again, but the best are the looseleaf varieties. They can be sown indoors in pots or tubs or sown outside direct into the bed. If sowing in a pot, sow thinly onto moist multi purpose compost, cover lightly with compost or vermiculite. Cropping can begin when the seedlings are about 3 inches high, scissors are the best way of harvesting the tender leaves, cut what you need, leaving about an inch of leaf at the base. When the whole pot of leaves has been harvested, give a liquid feed and in a few weeks you will get a second, if smaller harvest. Sow a pot of salad leaves every 2-3 weeks for continued harvests. If your sowing outside direct, sow in a shallow drill and cover with a half inch of fine soil. There is no need to thin out. Cut as before with scissors, and you should again get a second crop. Sow a 4 foot row every 2-3 weeks for crops all season. The use of cloches with lengthen the harvest if used at the beginning and near the end of the season. You can also sow your salad leaves direct into a greenhouse or polytunnel bed. Mixtures of different salad leaves are widely available.
Interplanting or Cropping with Lettuce
Lettuce or salad leaves can be sown or planted in between slower growing crops, this allows you to grow more in the same space. I often interplant lettuce with onions, tomatoes and young peas. The idea is that you grow lettuce in the space between the other plants and then crop your lettuce before the other plant grows tall or needs the room. It’s a great use of space if you have a small plot.
Pests and Diseases
Lettuce is generally trouble free, watch out for slugs when the seedlings are small. Keeping the lettuce plants free of weeds will help with deterring slugs and help reduce the problems of mold. Good airflow and plenty of water is what lettuces want. Lettuce doesn’t like very hot weather so plant with some shade in high summer. Watch out for aphids, again if the plants are clear of weeds and have good circulation, aphids should not be too much of a problem; you can prevent aphid infestation with home made garlic spray.
Although no lettuce is totally winter hardy, varieties like Valdor and Winter Density have some cold tolerance. All will need protection like a greenhouse and will not grow very fast without some heat. By sowing in Autumn and giving them winter protection, you can get an early crop in spring.