There are four main types of lettuce. Butterhead lettuces are globular, with soft leaves. Crisphead lettuces are also globular but have tightly packed, iceberg-style hearts. Both these types can be difficult to grow so we’ll be starting you off with loose-leaf lettuce, a “cut and come again” type of lettuce that’s kind to beginners. The upright, cos lettuces are also pretty straightforward to grow. Unlike the loose-leaf varieties, cos lettuces are harvested whole.
Lesson 1: Sowing the Seeds
1.1) Time to Sow
Lettuces need plenty of sunlight but can “bolt” if they get too much, so a partially shaded area is best. Dig the plot over thoroughly, get rid of stones and mix in well-rotted manure or compost to help water-retention and bolster nutrients. Rake the soil to create a fine tilth (surface soil that’s ready to plant). Use your hoe to form a channel, or “drill”, 1cm-1.5cm deep. Mark the course of your drill beforehand with garden twine and stakes to avoid wobbly rows of lettuces. Thinly sow (10-12 seeds over 30cm) the drill, cover with fine soil. Firm, label and water. Space rows 30cm apart. Don’t plant all your lettuce seeds at once. Save some for later. There’s more about this in later modules.
1.2) Container Crop
Loose-leaf lettuce is an ideal crop to try in containers. Use soil-based multipurpose soilless compost and sow at the same depth as for sowing in a conventional bed. Sow groups of seeds around 5cm-10cm apart. You’ll thin the seedlings out later. Don’t be stingy with your container size. You need one that’s at least 45cm wide and 45cm deep.
1.3) Try These
“Salad Bowl” is a reliable loose-leaf lettuce. “Lollo Rossa” is another steady loose-leaf variety. The reddish, frilled leaves are attractive as well as tasty. “Lobjoit’s Green” is a proven performer among the Cos lettuces. “Little Gem” is a fast-maturing Cos variety. Another strategy is to buy a packet of assorted loose-leaf seeds. That way, you’ll be harvesting ready-mixed green salad come the summer.
Lesson 2: Thinning Lettuce Seedlings
2.1) Survival of the Fittest
Lettuce seedlings usually begin to appear between 1 and 2 weeks after planting. Once they’re large enough to handle, it’s time to thin your rows. Get on with this task – lettuces don’t respond well to overcrowding. Water the seedlings the day before you intend to begin thinning them out. When thinning, look along the row and choose the strongest seedlings, based on the spacings given below. Gradually remove the rest.
2.2) Spaced Out
A cos lettuce like “Lobjoit’s Green” will need to be spaced around 30cm from its neighbour. Smaller varieties such as “Little Gem” should be thinned so that they’re around 23cm apart. If you’re growing loose-leafed lettuce, thin the seedlings so that they produce a more closely packed row, with a plant every 15cm. “Salad Bowl” is a good loose-leafed variety to try growing in this fashion. Because it can tolerate closer spacing, loose-leaf lettuce is a good choice for containers. Again, aim for 15cm between plants.
2.3) Water Wisdom
Water the lettuces in dry weather, aiming to give them around 15 litres per square metre, per week. Do your watering in the morning if you can, so that the leaves are dry by dusk. If lettuce leaves are left wet overnight they are more prone to pick up diseases. Once you have thinned your rows to the correct spacing, you may want to consider using a mulch of organic material around the plants. This will keep down weeds and help to retain moisture. A “quick and dirty” alternative is a black plastic sheet with holes cut out for the plants. It may not be an attractive option but it is effective. Slugs and birds can threaten young lettuces. One non-chemical defence is to cover a young lettuce plant with a bottomless plastic drinks bottle.
Lesson 3: Looking After Lettuce
3.1) Slug Defences
Most lettuces are ready to harvest after eight weeks, so your crop still has a little way to go before it hits the salad bowl. Meanwhile, it’s up to you to protect young lettuces from slugs and snails determined to fill their own salad bowls! By now, the seedlings may have outgrown the bottomless water bottle defences suggested in Lesson 2. Other non-chemical strategies include surrounding plants with grit or protecting them with serrated rings cut from larger plastic bottles. Alternatively, you can try luring your enemies away from the plants by making a slug trap. Saw a plastic water bottle in two just below the neck. Invert the neck end, push it back into the other piece and fix with staples or tape. Fill this contraption with beer or a sweet drink and place it near your crop.
3.2) Second Chance Salad
Now is a good time to think about re-sowing, especially if you are growing upright cos lettuces. Loose-leaf varieties allow you to harvest salad leaves for weeks but a row of cos lettuces will tend to mature at the same time. Try sowing a few cos seeds at fortnightly intervals until the end of July. This strategy should give you regular supplies of cos lettuces until early autumn. Certain loose-leaf lettuces may begin to produce leaves big enough to eat after six weeks. Keep your eyes open for larger leaves and pick them, to encourage more growth.
3.3) Shady Characters
If you’re also growing climbing French beans, you might want to consider sowing later rows of lettuces next to them. The shade provided by the beans will help prevent the lettuces “bolting” (running to seed) as a result of too much exposure to the midsummer sun. Remember to keep weeds down by hoeing between rows. Finally, don’t forget that both the original crop and the new seedlings will need watering regularly, especially if the weather is dry.
Lesson 4: Harvesting Lettuce Crops
4.1) The Heart of the Platter
It’s time to bring out your best salad bowl! If you managed to get your cos lettuces in the ground during late April, you should be able to begin harvesting them around now. Look out for plants with firm hearts but don’t go squeezing them: this will damage their delicate structure. Instead, test for firmness by pressing down gently on the heart with the back of your hand. If you detect a decent heart, don’t hang around. Harvest it straight away. If you leave it much longer the lettuce will bolt (run to seed). Pull the whole plant up, despatch the root and lower leaves to the compost bin and enjoy!
4.2) Leaf Lore
Loose-leaf varieties tend to mature a little earlier than hearted lettuces. So you may have already sneaked the odd leaf on to your plate, in order to encourage growth. By now, though, varieties such as “Salad Bowl” and “Lollo Rossa” should be producing leaves more regularly. When harvesting, choose outer leaves and cut them close to the ground – it encourages growth. Even if you can’t eat all the leaves that are ready for harvesting, cut them anyway. You can give away the surplus or compost it. But leaving large leaves on the plant will inhibit growth. It’s best to harvest all types of lettuce in the cool of early morning or evening.
4.3) Salad Supply
As well as harvesting your existing crop, you should be tending the seedlings you sowed after Lesson 3. Treat them the same way you treated the first crop but be aware that they will have to endure drier, sunnier conditions than earlier lettuces. You’ll need to be on hand with that watering can! If you want an uninterrupted supply of cos lettuces later in the summer, find some time now to sow a few more seeds.
Lesson 5: Extending Your Lettuce Harvest
5.1) A Lettuce of One’s Own
Have you noticed anything different about your fridge recently? Yep, there’s been a big drop in the number of plastic bags it contains, now that a significant proportion of your salad is coming straight out of the garden! If you want to extend your lettuce-growing potential even further, try using the “catch-crop” technique. Catch-cropping is the practice of sowing rapidly maturing vegetables such as loose-leaf lettuce in the space left by harvested crops. If you’re following the carrot course and you’ve pulled all your early carrots, for example, you could sow some lettuces in that space – but you’ll have to get your skates on.
5.2) Heat Stroke
Remember that midsummer temperatures can be a challenge for lettuces, so don’t use them as a catch crop in positions where they’re going to suffer prolonged exposure to the sun. Taller plants like French beans, runner beans or sweetcorn are ideal for providing shade in these circumstances.
5.3) Garden Nasties
As veggies go, lettuces don’t have too many enemies. But, when something unpleasant gets hold of your crop, you’ll know all about it. If you don’t want to use chemicals against pests (after all, what’s the point of home-grown produce if it’s been exposed to chemicals?) you can do an awful lot to prevent them by meticulous vegetable plot maintenance. As a general rule, employ a zero-tolerance policy against weeds. Their presence encourages a number of pests and diseases. Don’t leave lettuce stumps in the ground once you’ve harvested the heads. They’ll rot and attract pests, especially root aphids. Water your lettuces regularly. Finally, some gardeners warn that you shouldn’t try to grow lettuces in soil previously occupied by chrysanthemums because this environment will attract root maggots.
Lesson 6: Growing Winter Lettuces
6.1) Lots of Lettuce
Your lettuce harvest will be well under way by now. Loose-leaf varieties should be regularly producing leaves and later sowings of cos lettuces ought to be approaching maturity. Bear in mind that lettuces get extra-thirsty as the summer really heats up, so don’t relax your watering regime. Now is the last chance to sow conventional summer varieties for harvesting in early autumn.
6.2) Winter Strategies
For an early winter crop, sow a variety such as “Avondefiance” in August. This mildew-resistant type is a so-called butterhead lettuce. It has the loosely-packed heart of many traditional “English” varieties. When the colder weather arrives at the end of September, cover the crop with cloches. The lettuces should be ready to harvest in November or December. If you’re looking to harvest lettuces in spring, try “Winter Density” a dwarf, cos-type lettuce similar in appearance to “Little Gem”. Sow in late summer or early autumn. Protect the crop with cloches during winter. Once winter’s over, thin the young plants to 15cm. They’ll be ready to eat in April. If you want to go the whole hog and grow lettuces for consumption in mid-winter, your only option is to use a greenhouse or other heated enclosure.