Romaine lettuce is one of the vegetables I want to grow in my container garden. I’ve written all the details one would need to start growing them in a container.

You can grow romaine lettuce in a container as long as you choose a good size. Romaine lettuce has shallow roots so it grows well in a container that is 6-12 inches deep. It’s an easy plant to grow especially as a beginner. You can start from seed or get the transplants from a garden center.

What are the different varieties available?

Romaine lettuce is a variety of lettuce that grows long light to dark green leaves attached to a thick stem.

They are a crunchy variety of lettuce that grows in cool weather. Many types of romaine lettuce are also heat-tolerant.

You can get different varieties of romaine lettuce that may be green or red in color.

Some green varieties you can find are Parris Island Cos, Little Gem, Barcarole, Jericho, and Little Caesar. The Little Gem variety is small and tolerant to heat.

Some red varieties of romaine lettuce include Red Romaine, Cimmaron, Petite Rouge, and De Morges Braun. The Petite Rouge is a baby romaine lettuce with red-tinged green leaves.

When is the best time to grow romaine lettuce?

The best time to grow romaine lettuce is when the temperature is between 50 to 75 °F. There are some romaine lettuce varieties that tolerate heat. But when it gets too hot, the plant will not survive.

You can start growing romaine lettuce two weeks before the last frost date. You can grow them in fall as well but make sure it’s eight weeks before the first frost hits your area.

How long does romaine lettuce take to grow?

Baby romaine lettuce can take about 55-65 days to grow. Romaine lettuce can take about 65-80 days to grow.

You should check the seed packets to know how many days it will take for the romaine lettuce to hit maturity.

You can keep harvesting the outer leaves for your salads while allowing the main plant to continue growing.

You don’t want to harvest the romaine lettuce too late because the leaves will no longer be crisp when they’re ripe.

Once the harvest dates come close, you can check your romaine lettuce every day. Press the leaves and if they compress, the romaine lettuce is tender. Once it matures, the leaves are hard to compress.

Another tip to figure out if the romaine lettuce has grown is to check the height of the plant. If it reaches 6-7 inches in height, that’s a good indication of maturity.

How to choose a container for romaine lettuce?

You should check the seed packets to know how many days it will take for the romaine lettuce to hit maturity.

The container you choose for growing romaine lettuce depends on the size of the variety you want to grow. Romaine lettuce has shallow roots so most varieties would do fine in a container that is 6-12 inches deep.

You should use a container that is 12 inches in diameter as it will help give good space for the romaine lettuce to grow. If you’re growing baby varieties, you can grow several plants in one container.

You can use any type of container for growing lettuce like plastic, terracotta, ceramic, or metal. The romaine lettuce plant likes its roots to stay moist but not too wet.

That’s why my suggestion is to use a terracotta pot for growing romaine lettuce. The porous nature of this pot helps the excess moisture evaporate. So you don’t need to worry about soggy roots damaging the plant.

Whatever container you pick, make sure it has plenty of drainage holes at the bottom to remove the excess water. If the containers don’t have such holes, you’ll need to drill some yourself.

How to prepare the container for planting?

Once you’ve selected the right container for your lettuce plants, you need to clean them up before use.

I would recommend soaking the container in a mixture of 1 parts bleach to 10 parts water for at least an hour. You then need to wash the container with water and dry it before use.

This will ensure that there are no harmful pests and diseases lurking around in the container to harm your romaine lettuce plant.

Make sure the container has drainage holes at the bottom or drill some using a drill or hammer and nails.

You need to add potting soil to the container. So cover the bottom of the container with a rag or newspaper. This will prevent the potting soil from washing away when you water the container.

I would recommend using a potting soil you bought from a garden center rather than garden soil. Because garden soil may contain too much clay or sand not suitable for the plants. It can also contain pests, diseases, and chemicals.

You can make your own potting soil using 1 part compost, 1 part vermiculite, and 1 part perlite. The compost provides nutrients, microorganisms, and texture to the soil. The vermiculite and perlite make the soil permeable which helps it retain moisture while draining the excess water.

Fill the container with the potting soil till there’s a space of 2 inches left from the rim. This will prevent the soil from spilling out when watering.

If you’re growing romaine lettuce indoors, the balcony, or patio, it’s good to keep a tray beneath the container. This will collect the excess water that drains out when watering the plant instead of dripping on the floor.

How to plant the romaine lettuce seeds?

You can get the romaine lettuce seeds from a seed catalog online or a local garden center. The benefit of growing from seeds is you get a lot more varieties. And it’s inexpensive compared to buying seedlings.

You have a choice to grow the romaine lettuce indoors by starting seeds. Or you can directly sow the seeds in the containers.

My suggestion is to start seeds indoors because you can protect the seeds and increase the germination rates.

To start seeds indoors, you need to use seed starting trays. Put some seed starting mix in the tray. Then plant 2-3 romaine lettuce seeds 1/4th inch into the mix.

Water the soil gently to make the seed starting mix moist. You need to be careful not to dislodge the seeds from their position.

Romaine lettuce seeds have the best chance of germination when you keep the soil moist but not soggy. The seeds will germinate after about two weeks.

Then you need to provide sufficient light for the seedlings to grow. You can either use indoor lights or place the trays on a windowsill that gets plenty of sunlight.

Once the seedlings have grown 3-4 inches tall, you can transplant them to a container. But before you do that you need to harden the seedlings.

2-3 days before transplanting the seedlings, start to move them outdoors for a few hours every day. Make sure they are not in full sunlight or wind.

Once the seedlings are hardened, you can transplant them to a container. Gently squeeze the tray till the soil ball gets loose.

Make a hole in the center of the potting soil in the container and place the seedling in it. Cover the roots with potting soil so they are not exposed to air. You want each plant to be 4-6 inches apart from each other so they get sufficient growing space.

Press the soil near the base of the plant to give it steady support. Water the soil well so that the roots get enough moisture and adapt to the transplant.

How to plant the romaine lettuce seedlings?

If you want to speed up the process, you can buy the seedlings from a local garden center or nursery. But your choices of romaine lettuce varieties are limited by what is available.

2-3 days before transplanting the seedlings to the container, start to move them outdoors for a few hours every day. Make sure they are not in full sunlight or wind.

Once the seedlings are hardened, you can transplant them to a container. Gently squeeze the tray till the soil ball gets loose.

Make a hole in the center of the potting soil in the container and place the seedling in it. Cover the roots with potting soil so they are not exposed to air. You want each plant to be 4-6 inches apart from each other so they get sufficient growing space.

Press the soil near the base of the plant to give it steady support. Water the soil well so that the roots get enough moisture and adapt to the transplant.

How much sunlight does romaine lettuce need?

Romaine lettuce can grow in full sun or partial shade. But I would suggest giving the plant about 4 hours of morning sunlight. This gives it the best chance of growing well.

You don’t want to expose the plants to more than 7 hours of direct sunlight because the soil will dry out. And the leaves will begin to suffer damage with the heat.

The best thing to do is to move the container in a shaded part of the garden in the afternoon. That’s one of the benefits of growing romaine lettuce in a container.

How to water the romaine lettuce in pots?

Romaine lettuce contains about 95% water so you need to provide the plant with good moisture. This ensures that the plants will grow well and the leaves will be crispy.

You want to avoid the problem of overwatering or underwatering the plants in the containers. Underwatering will not provide sufficient moisture so the romaine lettuce will not grow well or even die. Overwatering will drown the roots, leading to root rot and fungal diseases.

My advice is to check the soil in the container every day in the morning. You can push your finger about 2-4 inches in the soil. If you don’t feel moisture at the tip of your finger, it’s time to water the soil.

Water the potting soil slowly and thoroughly so the water can reach to the lower levels of the container.

I suggest watering the romaine lettuce plants in the morning because the roots will get plenty of time to absorb the moisture and nutrients before the sun dries out the soil. And the excess water on the plant has time to dry out.

You could water in the evening if that is the only time you have. But make sure not to leave any water on the plants because that may invite fungal diseases.

You can use a watering-can for watering your romaine lettuce plants. Or you can set up a self-watering container. You could even use a drip irrigation system if you have several plants in your container garden.

I would also suggest using mulch like dried leaves, grass clippings, or moss in your container. This will help keep the soil moist longer while protecting the plants from pests and weeds.

How to thin the romaine lettuce seedlings?

When you start growing your romaine lettuce plants from seeds, you don’t know how well they will germinate. That’s why you plant at least 2-3 seeds per hole.

The idea is that this increases the chances that at least one of the seeds will germinate after the 2 weeks have passed.

If more than one seeds germinate, you need to choose the one that looks the healthiest. You can pull out the other seedlings and toss them into your salad or compost pile if you have one. This process is known as thinning.

You should also do the thinning if the plants are growing too close to each other and may end up fighting for the nutrients. It’s best to keep the romaine lettuce plants 4-6 inches away from each other.

You can do this thinning once the seeds have germinated and at least 3-4 leaves have grown on the seedlings. They may have reached a height of 2-4 inches when you can do this.

When you buy the seedlings from a garden center or nursery, you won’t have to worry about this. You need to spend your efforts on choosing the healthiest plant you can find at the garden center.

How to fertilize romaine lettuce plants?

If you start seeds, then you don’t need to worry about fertilizing at first. The seeds contain their own nutrition that will last them for the 2 weeks till germination.

But once the seeds have germinated or you’re transplanting the seedlings to a container, it’s good to use fertilizer. The best thing to do would be to mix compost with your potting mix.

The compost is rich in organic matter as well as the beneficial microorganisms that will provide the required nutrients to your romaine lettuce plants. You can add a little bit of compost every 2-4 weeks to the soil to keep getting the nutrients.

If you don’t have compost, you can use a slow-release organic fertilizer in the potting mix when transplanting. This will provide nutrients to the plants for a few weeks.

You can choose a balanced fertilizer that has an N-P-K of 5-5-5 or 10-10-10. This means it contains equal amounts of nitrogen, phosphorus, and potassium for your plants. The fertilizer will release slowly into the soil when you water the plants.

Once the plants have matured to about 4 weeks, you can add an organic liquid fertilizer to the soil and foliage. You can spray this fertilizer every 2 weeks to get the best growth of your romaine lettuce plants.

How to harvest the romaine lettuce from pots?

The best thing about growing leafy vegetables like romaine lettuce is you get to eat them pretty fast.

The best time to harvest the leaves is when they are tender and not fully mature. If you harvest the leaves in the morning they will be crunchy and full of flavor. Once the sun comes out the leaves tend to lose their crunch and may even wilt.

You could harvest the baby romaine lettuce as soon as they have grown a little. They are crunchy, tender, full of flavor, and packed with nutrients.

You can harvest the outer leaves of the romaine lettuce as the plant is growing. Use a knife or pair of scissors to cut the 3-4 outer leaves from each plant.

Just keep the inner leaves and stem growing so they keep producing more leaves for harvesting. You can continue to harvest the leaves until the plant stops producing at the end of the growing season.

You can also harvest the entire head of the romaine lettuce once it’s mature enough. You can use a knife or a pair of scissors to cut the head. Cut the stem from the base of the plant just beneath the leaves.

Tip: If you harvest the romaine lettuce when the first frost hits, they will be even more crunchy and flavorful.

Once you’ve harvested the romaine lettuce leaves you can clean them with cold water and dry them out. Then store them in the refrigerator. The harvested leaves will last about a week in the refrigerator before they begin to wilt.

What are some romaine lettuce pests and diseases?

There are plenty of pests and diseases that will try to attack romaine lettuce plants. The advantage of growing them in containers is that we can keep a close eye on them.

I suggest checking your plants every morning as part of your watering schedule. This will save you time and take care of any issues as soon as possible.

Aphids

These are small pests that love to attack leaves of plants especially leafy ones like romaine lettuce. You should check your leaves and the undersides for signs of these bugs. They can be of different colors like green, yellow, red, or white.

It’s easy to get rid of aphids using a spray of water and dislodging them on to the ground. You can also use insecticidal soap on your leaves to get rid of them.

Slugs and snails

These are another set of pests that love to chomp on leafy vegetables. They will manage to reach the romaine lettuce even if you grow them in a container.

A solution to get rid of slugs is to crush eggshells and put them on the soil. This can cut up their fragile bodies and deter them from reaching the plants.

You can also place a beer trap that attracts slugs and snails. They have a drink and end up drowning in the trap.

Powdery mildew

This is a fungal growth that can affect the older leaves of the romaine lettuce. It causes the leaves to turn yellow or brown. It requires a humid environment to grow on the plants.

The best way to prevent this is to be careful not to splash water on the foliage. This increases the chances of fungal diseases affecting the plant.

If your plant gets powdery mildew, you can use sulfur to try and treat the problem.

Leaf spot

This is another type of fungal disease that can affect your romaine lettuce leaves. It causes brown spots on the leaves that dry out. If the infection is severe, the leaves wilt and die.

You can prevent this disease by keeping your leaves free from moisture. Be careful when watering the plants so the water does not splash on the leaves.

The only solution to this problem is the prevention of the disease. You can try to get seeds that are free from this pathogen.