Lettuce (leitís) – Difficulty: Easy – Time to harvest: 10-12 weeks
Lettuce is one the easiest vegetables to grow and can be grown all year round. The foundation of great salads, homegrown is more convenient as lettuce doesn’t store well. Homegrown lettuce is also far superior in taste to shop-bought. Lettuce is a plant of the daisy family (Asteraceae).
Lettuce doesn’t do well in extreme heat which makes them perfect for our mild climate. Read on for the ultimate guide on growing lettuce in Ireland.
Butterhead are rose-like in shape and take around 65 days to mature. They have a sweet flavour and soft leaves. They are tolerant of poor growing conditions. Leaves can be harvested from the outside while they are growing.
Romaine/Cos grow in a long oblong shape and tolerate heat better than other varieties. They take 75-80 days to mature. Leaves can be taken from the outside while growing.
Crisphead are round and give extremely crisp leaves. It takes 70+ days to mature.
Loose leaf is one the easiest lettuces and low maintenance varieties. It is great for container planting as it needs less space. The outer leaves can be easily harvested while growing or matured.
All year round is a great butterhead variety with a sweet flavour. As the name suggests, it can be grown all year if protected in the colder months.
Little gem is a popular variety of romaine/cos lettuce. It has crisp, crunchy leaves and a beautiful sweet taste.
Iceberg is the most recognisable type of crisphead lettuce. With its crisp leaves you can even replace bread with it in a sandwich.
Lollo Rossa is a red loose leaf with frilly leaves and wonderful flavour. It is a great choice for a cut and come lettuce. I highly recommend this lettuce for taste, ease of growing and being moderately slug resistant.
The seeds are small, oblong and about 3-4 mm in length. Packet seeds should keep for 3 or more years. Seeds harvested yourself will keep for 6 years.
It is easy to save lettuce seed as it is prone to bolting. The flowers are ready to harvest when brown coloured with cotton puffs on top. Cut off the head and turn upside down with something underneath to catch the seeds. Gently rub your fingers between the fluffy chaff to release the seeds.
Another option is to place the seed head into a large bag or container and vigorously shake. Put the seeds in a fine-mesh strainer to further remove the chaff and stalks.
Leave to dry completely for a few days and store in a container in a dry cool place. Avoid saving hybrid varieties as they are most likely sterile.
Location and soil
Lettuce does best in sun with light shade. In summer try planting in a shaded area to slow bolting. Place taller plants like peas, beans or tomatoes alongside it to provide shade.
Lettuce doesn’t like acidic soil so keep your soil pH level between 6.5. and 6.8. Rich soil is best but it will grow well in average conditions. Make sure the soil is well-drained as it rots in waterlogged soil.
In advance of planting, work in rotted organic material like homegrown compost. In rich soil lettuce will not need additional feeding. Lettuce favours high nitrogen soil. Fertilise with fish emulsion or seaweed. Don’t overfeed nitrogen or the leaves will taste bitter.
Lettuce can germinate at low temperatures but is best in a range of 16-18c. In 24 degrees and over, it just won’t sprout. Choose a shed or outside to germinate, instead of a greenhouse in summer. In good conditions lettuce can germinate in only 3-4 days.
Fill and firm a modular tray with compost and water well. Lightly indent each cell and sow your seeds. For a head of lettuce sow one seed per cell. If sowing loose leaf, sow 3-4 seeds.
Cover with a very sparse layer of compost. It is important for lettuce seeds to have light to germinate.
Thin out by gently pulling the weakest seedling, leaving only one seedling per pot. After 4 weeks or when 10cm in height, transplant outdoors or into a bigger container. For a continuous supply sow every two weeks.
If using seedlings grown indoors, harden off by leaving out every day for a week, bringing them in at night. Dig small holes in a row 15cm apart. Place the seedling into the hole and fill in with compost. Space rows over 20cm apart. For single head varieties sow 35 cm apart.
Don’t bury any leaves underground. If the lettuce is too deep, it will develop stem rot. The lettuce should be level with the soil but firmly placed. Too far away or loose from the soil it will dry out.
To sow directly into soil, sow seed shallowly, only 1cm into the soil. Space sowings 15cm apart. The seedlings may need to be protected from birds and other pests.
Growing in containers
Lettuce is perfect for growing is containers as it has shallow roots. Choose a container around 15 cm deep. A container high off the ground is less likely to be attacked by slugs.
A window box is a wonderful container for loose leaf lettuce. Put it on your kitchen windowsill for quick access.
As Lettuce roots only go 7-10cm deep, it needs consistent light watering. To check if it needs water, stick your finger 2cm into the soil, if dry, water it.
In the last two weeks before harvest, it is important to water or they may go to seed before completing maturity.
Weed by hand as lettuce has shallow roots. Pick out weeds before they have a chance to grow and settle. Place mulch around the plants to suppress weed growth.
In weather above 24 degrees, lettuce will bolt. Bolting is when the plant goes to seed, it shoots up tall stalks with flowerheads on top. Bolting turns the leaves bitter, so it’s best to throw the whole plant away.
Harvest and Storage
Varieties with a head should be cut at the base. Check and thoroughly wash the headed varieties in case of hidden slugs.
For loose leaf cut and come, take the leaves on the outside of the plant. Pinch the leaves off at the stem or cut with scissors. Don’t take too many or you will kill your plant. You can harvest whole young plants by cutting 2cm above the base, they should regrow several times.
Lettuce doesn’t keep well, so it’s best to pick when needed. To keep fresher for longer wash your lettuce with cold water and dry thoroughly in a salad spinner. Keep in a paper or plastic bag with a sheet of kitchen roll and place in the refrigerator crisper drawer. Lettuce is gone bad when the leaves are slimy, brown and smell.
Slugs and snails
Slugs and snails are the biggest nuisance for lettuce. They will take large chunks out of the leaves and hide between the layers. I find slugs are more attracted to green lettuce varieties, try planting red varieties like lollo rossa.
Slugs tend to come out at night and after heavy rain. Go out in a wet evening and collect them into a bucket, disposing of them well away from your plants.
Border your lettuce with eggshells, diatomaceous earth or sharp lawn edging. Slugs dislike crawling on jagged surfaces. Clear the surrounding areas of places that the slugs lurk, like plant containers, leaves and wooden planks,
If all else fails, consider growing in containers high off the ground or tall planters lined with copper tape.
Lettuce root aphid
If your lettuce looks wilted, or the growth is stunted, you may have encountered the root aphid. When the plant is pulled up, you see a white powder coating the roots and possibly maggots. Another sign is ants swarming around the roots, attracted by the honeydew the aphids produce. If your garden patch has suffered from this, avoid planting lettuce in that spot for two years.
Blast off the aphids with the garden hose, you can cover your lettuce with a fine mesh from June to August to avoid the aphids.
To prevent aphids, slugs and snails spray the roots of your lettuce with garlic spray weekly. Avoid spraying close to harvest and wash the leaves well before eating.
Garlic spray recipe
- 1 litre of water
- 2 whole garlic bulbs
- Washing up liquid
Crush the garlic and put into a pot with the water. Boil for 3 minutes and strain several times through a fine mesh sieve or a cheesecloth. Optionally add a few drops of washing up liquid. Decant into a spray bottle and use weekly.
Good companions are carrots as they root deep while lettuce is very shallow. Garlic, onion, chives and other alluims help repel aphids.
Lettuce isn’t forming heads
It may have no room to grow or it may be too hot for it to form.
Leaves are tinged brown
The result of underwatering or too hot of weather.
Find more vegetables in our Plant Encyclopedia