Top Of The Crops - Lettuce

Growing Lettuce In A Polytunnel

Lettuce is one of the easiest crops for beginners and one of the best plants for polytunnel growing. 

Lettuce comes in a wide range of different varieties, hearted or loose leaf. Cut and come again varieties provide a quick crop for endless summer salads. 

It can be planted in the ground in a polytunnel, in containers or even in vertical gardens or baskets hanging from the crop bars. Since it can be grown in small spaces, lettuce can help you make the most of the space in your polytunnel or elsewhere in your garden. 

The Preferred Conditions for Lettuce

While lettuce will like a sunny spot in the spring, by the time summer rolls around, the sun may be too fierce and many types of lettuce can be prone to bolting and going to seed. To minimise the risk of lettuces going to seed, you can sow it in the shade of other, taller plants. 

Grow lettuce in the ground, raised beds or containers. Wherever you grow them, make sure that the medium is reasonably fertile, with plenty of organic matter, and moist yet free-draining. 

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

How to Grow Lettuce 

Lettuce is one of the easiest crops to grow. It is usually grown from seed, which can either be sown indoors for later transplantation, or sown directly where the crop is to grow. 

You can:

  • Grow lettuce as micro-greens, harvesting while the leaves are still very small. 

  • Grow baby-leaf lettuce, harvesting between around 4 and 6 weeks. 

  • Grow full heads of lettuce, harvesting at maturity. 

Sowing Lettuce Seeds

Lettuce can be sown almost all year round indoors or under cover. There are types that are best suited to summer growing and others that will happily overwinter with just a little protection. 

Typically, gardeners will succession sow lettuce in spring and early summer for a spring/ summer crop, and in late summer or early autumn for an autumn harvest, or for overwintering. 

Sow lettuce little and often to get a continuous crop – sow seeds thinly every couple of weeks to make sure you have a steady supply. 

Lettuce seeds will germinate best when sown at temperatures between 16 and 20 degrees Celsius and not higher than 21 degrees Celsius. 

Place the lettuce seeds on a moist yet free-draining potting mix and cover lightly with the same growing medium. They must only be covered very lightly because the seeds need light to germinate. 

The seeds should germinate within a week in most cases. It is best to sow a small number of seeds every 2 weeks to get a continual supply of fresh lettuce leaves from your indoor garden. This is better than sowing lots all at once and ending up with lettuce that you cannot eat. 

Sowing seeds indoors allows you to get started earlier and helps you avoid pest issues that can sometimes arise when direct sowing. Sow seeds indoors into seed trays, small pots or soil blocks. Lightly cover the seeds. Prick out heading lettuce seedlings if transplanting once they are large enough to handle, and place them into their own separate containers. Loose leaf types can be harvested for baby leaves without transplanting or thinning if desired. 

For hearted lettuces, when direct sowing, you will have to make sure that you thin seedlings as soon as the first true leaves appear. (You can eat thinned lettuces as a micro salad.) Continue to thin hearted lettuces until they are around 20cm apart. 

Some loose leaf lettuces should also be thinned to around this spacing, though for cut and come again varieties, spacing is not as important as long as there is enough nutrition in the soil or planting medium and the plants are provided with enough water.

Planting Lettuce

Lettuce that was sown outdoors can be planted out any time after the last frost date where you live, or even earlier if they have protection from a polytunnel or cloches. Remember to harden off young seedlings, gradually acclimatising them to outdoors conditions before placing them into their final growing positions. 

Plant into a well-prepared site, that has been weeded thoroughly and amended with plenty of homemade compost or other organic matter. Or, if you are growing in a container, plant into multi-purpose, peat-free potting mix. 

Note – alternatively, lettuce can be grown in water. As a leafy crop, lettuce is well-suited to hydroponic growing and other related growing techniques. Growing in water (especially as part of a small-scale aquaponics system) can be an interesting, water-wise, sustainable, and eco-friendly option to consider. 

How to Delay Bolting

When lettuces experience stress due to issues in the environment, and when temperatures rise above around 20 degrees C. they can rush to flower and produce seed prematurely. This is called bolting. 

Maintaining the optimal conditions for growth, such as watering correctly, and keeping the environment cool with shading and good ventilation/ air flow in summer can help to delay bolting and keep lettuce tasting good for longer. 

Harvesting Lettuce

Cut and come again varieties can be ready in as few as six weeks and you can keep picking individual leaves from the plants. Hearted lettuces will require a longer growing period and should be cut whole but can regrow a bit if you leave the base in place. 

If you choose the right varieties then you can be enjoying fresh salads from your garden, especially from a polytunnel, all year round.

Harvest early in the day where possible.

Preparing and Using Lettuce

Lettuce is not only an easy crop to grow. It is also very easy to prepare and use it. Usually, all you need to do in order to use your lettuce harvest is give the leaves a wash in some cold water, then spin or shake it dry. 

Lettuce is of course a key ingredient in salads of a range of types and especially when you are growing your own, salads definitely don't need to be boring. Lettuce also works well in sandwiches and wraps and the like, and you can even use it to make a chilled lettuce soup for summer if you have too much all at once. 

Storing Lettuce

Lettuce is one of those crops, however, that does not store well. You need to eat lettuce as soon after it has been harvested as possible. Store lettuce for no more than a few days in the crisper drawer at the bottom of your fridge. 

Care Tips for lettuce 

Lettuce is very easy to care for, as long as you keep its basic needs in mind. 


One thing you must do when growing lettuce, of course, is keep your crop well-watered through the warmest part of the year. Remember that plants in pots will need to be watered more frequently than those growing in a raised bed or in the ground. 

Aim to keep the soil consistently moist but also make sure that excess water can drain away freely. Try to water roots and not leaves and water only in the morning to reduce the chances of certain issues taking hold. 


Add an organic mulch around lettuces to conserve soil moisture, protect and enhance the soil, and keep weeds down to a degree. A good quality homemade compost is ideal for this. A nitrogen-rich mulch like grass clippings may also be helpful to this leafy plant over the summer months. 


Lettuce is forgiving of a little competition but make sure the crop is not swamped by weeds, pulling these carefully where they appear. Close spacing and creating groundcover with lettuce and other similar crops can help keep weed growth to a minimum. 


Remember that lettuces will bolt, and begin to flower, when they experience stress due to water shortage etc.. and when temperatures rise too high. Once the plant flowers, unfortunately, the leaves become bitter and not good to eat. So place your lettuce carefully and take good care of your crop to reduce the chances of bolting. 

It is worthwhile noting however that if you let some lettuce go to seed later in the year, it is easy enough to collect seed for next year. If you do not then you will have to buy new lettuce seed each year as it does not remain viable seed for long.

Varieties of Lettuce

Some highly regarded lettuce varieties to grow in the UK are:


‘Black-Seeded Simpson Improved’ 






‘Crisp Mint’ 






‘Little Gem’ 

‘Little Gem Delight’ 

‘Little Leprechaun’ 

‘Lobjoit's Green Cos’ 




‘New Red Fire’ 

‘Parris Island Cos’ 





‘Salad Bowl’



‘Winter Density’

All of the above have an award of garden merit from the RHS. 

There are many types of lettuce to choose from. 

Common Problems for Lettuce

Lettuce is a magnet for a range of pests, though in a healthy organic garden, serious infestations should be kept in check through natural predation. Look out for slugs and snails, aphids, root aphids , cutworms, and birds, that may peck at young seedlings in the spring. 

Aside from bolting, as discussed above, lettuce can also have certain fungal issues like grey mould. Ensure good air flow and spacing, and water at the base of the plant not on its leaves to reduce the chances of problems like this taking hold. 

Top Tips for Growing Lettuce in a Polytunnel 

  • Sow successionally so you do not end up with a glut. 

  • Companion plant to enhance growing conditions – e.g. plant companions to give lettuce some shade during the warmest part of the year. Grow nitrogen fixing legumes nearby. And plant for pest control with companion plants like radishes and aromatic herbs. 

  • Use lettuce as a companion plant to create groundcover around other crops, and to make the most of the space between slower-growing crops. 


What Is The Best Month To Plant Lettuce?
Does Lettuce Regrow After Cutting?
How Long Does It Take To Grow Lettuce?
What Not To Do When Growing Lettuce?


Misfits Market (2021) What’s The Difference Between Cabbage and Lettuce? [online] Available at: 

< Back

growing lettuce in a polytunnel