Growing lettuce in containers is a great solution if you only have a small garden, balcony or patio. If you are able to begin growing lettuce in pots indoors you are also able to get a head start on the growing season. This means that you will be able to enjoy fresh salad leaves even earlier.
There’s nothing better than being able to harvest fresh vegetables from just outside your door, and lettuce is one of the easiest vegetables to grow.
If you’re short on space or time, growing lettuce in pots is an excellent way to enjoy fresh salad greens. You can easily harvest a good amount of greens with just a few containers, and they can even grow in with flowers or other vegetables.
This guide to growing lettuce in containers will take you through everything you need to know to add this crop to your container garden or outdoor space.
When Should I Begin Growing Lettuce in Containers?
While some varieties, particularly of loose leaf plants, will tolerate heat, in general this is a cool weather crop.
These plants struggle to germinate in soil warmer than 75℉. It will also fail when covered in a frost. If you want an early start, sow seeds undercover before your last local frost date.
Unless you are growing lettuce in containers indoors, your USDA zone will dictate when you can plant lettuce.
Lettuce grows best in cool weather and is an early spring crop in most regions. If you live in a warm or tropical zone with mild winters, you will want to plant in fall for a winter crop.
For spring growing, plant after the danger of hard frost has passed, usually about 4 weeks before the average last frost date for your region. Most greens will tolerate a light frost, but a severe freeze will kill them.
For fall growing, plant about 4-6 weeks before the average first frost date for your region. Provide the plants with some shade during the hottest hours of the day until the weather starts to cool down.
Which Container is Best for Growing Lettuce in Pots?
The first step to growing lettuce in pots is choosing the right containers.
Lettuce grows easily in containers, even alongside other plants, but needs at least 6 inches of soil depth to grow well.
Because they have shallow roots, most lettuce varieties will grow well in long and shallow containers. They do need at least 6 inches of soil depth, so be sure to measure the pots you plan to use. You can also use circular pots that are at least 10-12 inches in diameter. Larger varieties will require a larger container.
The material of the pots does not matter. You can use plastic, terracotta, clay, etc. Just keep in mind that plastic is the lightest weight and will be easier to move when it’s filled with soil.
One of the most important steps when choosing your pots is making sure they have drainage holes in the bottom. Otherwise, your plants are likely to become water-logged and unhealthy. If they aren’t already there, you can drill drainage holes in the bottom if the material permits.
The key to successfully growing lettuce in containers is keeping the soil consistently moist but not wet. Lettuce roots dislike being overly wet and this can cause the plants to fail. The soil should be loose and well worked. Mixing sand or other material to lighten the soil when growing lettuce in containers can also help.
Clay containers are best as they have a permeable surface. Growing lettuce in containers this way enables excess water to evaporate helping to prevent overly soggy roots. However with a little extra care you can be just as successful cultivating the crop in plastic containers.
Make sure your container is large enough to comfortably hold the variety you are growing. A pot that is too small will cause the plant to become pot bound. This, in turn, can cause plants to become stunted or unhealthy.
Positioning your Containers
Growing lettuce in containers requires sun. However your chosen position should provide the plants with some shade from the intense midday sun.
Preparing the Pots for Planting
Once you’ve picked out the pots you’ll be using, you’re all set to fill them up and start growing your container garden.
Before adding any soil to your pots, you’ll want to first cover the drainage holes at the bottom. Use small pieces of an old rag or cloth to make sure each hole is covered. Growing lettuce in containers this way allows excess water to drain out of each container without taking your soil with it.
Choose a good quality potting mix or garden soil to fill the containers with. Look for something that contains organic matter to provide nutrients and a material like perlite to provide good aeration and drainage.
If you don’t want to fertilize as the plants grow, many potting mixes come with a slow-release fertilizer already added in. I also frequently use a combination of organic potting mix and homemade compost to make sure my plants will have lots of nutrients to keep them growing.
Fill your pots almost to the top with your chosen soil mix, leaving an inch or two of space to prevent soil from washing over the sides later. Now, you’re ready to plant!
Before planting, you should choose which variety or varieties you want to grow. There are many different ones to choose from, each with its own unique flavor, texture, and appearance.
There are several different varieties of lettuce to choose from. Here are some of the most popular:
- Celtuce – grown for its stem, much like celery, instead of the leaf.
- Butterhead– This is one of my favorite varieties that produces soft leaves and a loose head. The leaves are mild and sweet with a very delicate flavor.
- Romaine– This is a very familiar variety known for being used in Caesar salads. It grows in a more upright habit than other varieties and has sturdy, crisp leaves. Romaine has a wide range of cultivars to choose from. This variety tends to produce leaves around a tight centre, forming a loose ball. Romaine’s can tolerate some heat and will take up to 85 days to fully mature.
- Loose Leaf– This is one of the easiest kinds to grow and a good choice if this is your first time growing lettuce. Loose leaf does not form a tight head and is one of the quickest varieties to mature. The flavor tends to be mild but stronger than butterhead. Some cultivars will also happily tolerate hot weather, meaning they can be grown in a range of USDA zones. Maturing within 45 days, their names come from the plant’s loose growth habit, it is not as compact as other varieties.
- Crisphead– Like the name suggests, this variety forms large, firm heads. Leaves are paler and have less flavor than other varieties. The most recognizable type is iceberg. Crisphead takes the largest to mature and is the hardest to grow in pots. Crisphead cultivars include some of the most commonly grown types such as Iceberg. Crispheads prefer to grow in cool temperatures.
The distinctive shape of Romaines. The growth habit of this variety is more compact than other varieties. However they will struggle in warmer conditions.
Seeds vs. Transplants
Lettuce is a crop that grows very well both from seed and as a transplant.
Growing from seed gives you many more options when it comes to variety. Seed catalogs offer hundreds of different types of salad greens, whereas your local grower will probably only offer a few varieties as seedlings.
Buying seeds is also more cost effective, but it does require a little more work and care. Seeds need extra attention to make sure they germinate and will need to be thinned to get the proper spacing.
Growing seedlings is a much simpler method as long as you are happy with the varieties offered by your local nursery or garden center. You can also combine the two methods by germinating your seeds indoors and transplanting the seedlings into pots.
Starting Seeds Indoors
If you choose to start seeds indoors, sow them in flats or starter trays about 3-4 weeks before you plan to transplant. Fill flats with a seed starting mix and place seeds about ¼ inch deep. Water the flats and place them somewhere cool, keeping in mind that lettuce won’t germinate well at temperatures above 75° F.
Continue to keep the soil damp but not soaked. Once seeds have germinated, move them under grow lights (fluorescent lights work fine), or place them in a sunny part of your home where they will get plenty of light.
Once your seedlings get this big, it’s time to harden them off before you transplant them into pots.
You’ll want to make sure the soil does not dry out because your new seedlings don’t have a very big root system. Water the soil around the seedlings gently. Try to avoid getting the leaves wet since this invites the growth of unfriendly pathogens that may kill your new plants.
Good air circulation is one of the best ways to prevent seedling-killing conditions such as damping off. I have a small room fan that I use to get air circulation around new plants. Running it for 10-15 minutes a few times a day is more than enough.
About 2-3 days before your planned planting time, start hardening off your seedlings. Take them outside for a few hours each day but bring them back inside at night. Keep them out of intense sunlight for long periods of time and any extremely cold temperatures.
Once your lettuce seedlings have been hardened, it’s time to start growing them in your pots!
Planting Your Containers
Whether you started your transplants from seed or bought them locally, planting your lettuce is the fun part.
Start by deciding how many plants you want in each of your pots. As a general rule of thumb, space seedlings 4-6 inches apart if you plan to harvest frequently. If you are growing head lettuce that needs to fully mature before being harvested, you’ll need to space plants 12-18 inches apart.
A simple tip is to use small stones to lay out how you think you want your planting to end up. That way you can work out the spacing before digging up any dirt.
Once you have your plan, dig a small hole that will fit your transplant and gently remove the seedling from its container. If the plant is root-bound, loosen the roots with your fingers before placing it in the hole.
You want the soil of each transplant to end up just below the soil in your container. Cover the root area with a little potting mix and firm around it with your hands. Repeat this process until each pot is full.
It’s very important to water in your new plants. Even if the soil is already damp, watering will help them get established quickly and start growing. If your watering exposes any roots, be sure to cover them back up with soil.
If you want to sow seeds instead of transplanting, sow each seed ¼-½ inch deep and cover lightly with soil. Keep the soil moist until the seeds germinate. After a few days, thin the seedlings to 4-6 inches apart and continue to let them grow.
For a continuous supply of lettuce, plant seedlings or sow seeds every 2-3 weeks.
Caring for Your Growing Plants
Lettuce will grow most quickly in full sun, but it’s one of the few vegetables that also grows well in part shade. In fact, if you are growing it in warmer weather, place your pots where they will get morning sun and shade in the afternoon.
As your plants grow, make sure they get adequate water. Lettuce leaves are mainly made up of water and need enough hydration to keep their tenderness.
Check your pots regularly to make sure that the top few inches of soil have not dried out. You don’t want to overwater and drown your plants, but you do want the soil to stay consistently moist. Shallow pots will need to be watered more frequently than deeper ones. Applying a layer of organic mulch, such as homemade compost will help the soil to retain moisture.
Apart from watering, lettuce plants will grow pretty well on their own. They often will grow fine without fertilizer, especially if your potting mix contains compost. However, you can fertilize after a few weeks with an organic liquid fertilizer if they aren’t growing as much as you want or make your own fertilizer.
Sometimes, hard frosts will show up when they aren’t supposed to. If this happens, just cover your pots with a gardening fabric or an old sheet overnight for protection.
How to Avoid Bolt When You Grow Lettuce
Bolt is when a crop prematurely matures and begins producing seed. This is usually caused by an increase in temperature. Bolt can also cause leaves to develop a bitter taste.
Some varieties are more bolt resistant than others.
You can try to delay or prevent bolt in a couple of ways. Planting as early as possible, maybe even starting seeds undercover and transplanting out following the last frost date, is one way. Succession planting can also help.
Aim to keep the plant, and the soil around it, as cool and damp as possible. This can be done in a number of ways and helps to prevent bolt. Once crops have bolted they will lose their pleasant flavor and texture.
Positioning growing lettuce in pots away from the mid-morning to late afternoon sun will help to keep the crop cool. This also helps to delay bolt.
Mulching the soil, particularly with an organic mulch such as homemade compost, will also help to keep the soil cool.
Keep the soil as weed free as possible. Weeds are fast to emerge. They can quickly smother other crops, particularly young plants.
Companion planting is the process of cultivating mutually beneficial plants alongside each other. Salad leaves and plants tend to make great companions for each other. With the right timing they will all be ready for harvest at the same time, allowing you to enjoy a fresh, homegrown salad.
Herbs such as parsley will also benefit your crops, particularly because some herbs will act as pest magnets, preventing your leaves from becoming infected. Finally if you want to add a bit of color to the containers add some violas. As well as being colorful the flowers are also edible.
Dealing With Pests
I have many seasons where my lettuce crop makes it pest-free, but that’s not always the case.
Aphids are the most common pest that attacks lettuce. They are small insects that hide out on the underside of the leaves and feed on the plant. Most of the aphids I deal with are green, so you may have trouble spotting them unless you look closely. They can also be several other colors including brown, orange, or white.
Typically, aphids will not do enough damage to severely harm your plants before you’ve gotten a good harvest. However, be sure to wash the leaves thoroughly so that you don’t eat any by accident.
Regularly check your plants for signs of infestations. Wash away pests with a blast from a hosepipe or an application of soapy water. You can also make an insecticidal soap which will rid your plants of problematic infestations.
Slugs love lettuce and can do a large amount of damage in a short amount of time. Putting crushed up eggshells around your plants is a natural way to discourage slugs.
Slugs and snails love lettuce leaves. I have more problems with slugs when I’m growing lettuce in the garden, but they can still crawl into your pots and do a lot of damage.
If you are noticing slug damage, try spreading crushed egg shells around each plant. The sharp surface of the egg shells is often enough to discourage slugs.
As well as chemical controls, organic methods such as beer traps will protect your crops. Wrapping copper tape around a container will prevent many of the pests from accessing your crops.
Harvesting Your Lettuce
Now that you’ve put in all the hard work, it’s time to enjoy your harvest.
The best time to harvest growing lettuce in containers and pots is in the early morning before they lose any of their moisture content. As the day warms up the sun can cause tender leaves to wilt. Leaves harvested in the morning taste and look better.
You’ll also get the best tasting leaves during the coolest weather. Once the weather warms, the plants start to bolt and the leaves become bitter.
There’s no need to wait until your lettuce plants are their full size to start harvesting (unless you are growing head lettuce). Once the leaves reach a good size for eating, you can start picking them.
Harvest the outer leaves by picking or cutting them right where they meet the stem. You can usually pick 3-5 leaves from each plant. Just be sure to leave the center leaves alone so that the plant will keep growing and producing. Cut leaves away with a sharp scissors or knife. If you are harvesting the entire head firmly grip the plant and pull it from the soil. Be careful not to disturb the roots of neighboring plants as you harvest. Individual leaves, but not whole heads, will continue to grow after harvest.
If you do want a full size head, let each plant keep growing until it reaches maturity. Then, cut them off at the base, right above the soil line.
Now that you’ve done the hard work of growing lettuce, it’s time to enjoy it. After harvesting the leaves, rinse them off under cool water. Use them immediately in a fresh salad or store in the refrigerator for up to a week.
After harvesting your lettuce, wash it using cool water and shake most of the excess water off. Use it immediately or store in a plastic bag in your refrigerator.
Wrapping a damp cloth or paper towel around the leaves can help them last longer and stay fresher in the fridge. Just don’t get it too wet or the leaves will start to rot. Typically, lettuce will last for about a week when refrigerated.
Growing lettuce in containers is a great way to enjoy this popular salad crop. Not only is it a great solution for container gardens, or gardeners with limited space, it is also beneficial for gardeners in difficult climates.
Growing lettuce in containers allows you to shelter plants during warm periods, helping to prevent plants from bolting. Additionally growing lettuce in pot undercover will enable you to enjoy this crop throughout the fall and winter months. To make the most of your container space, plant lettuce around other veggies like cucumbers. With a little care and the right container setup, you’ll have a fresh supply of greens that will last for months.