10 Tips For Growing a Bountiful Lettuce Harvest in Containers

I just love a healthful and nutrient-rich salad. And what is a salad without a tender, crunchy foundation of leafy lettuce to set the stage for a wide variety of veggies? Lettuce is an easy drop to grow, as long as you keep a few factors in mind in terms of environment and maintenance. In fact, some types of lettuce can be harvested more than once in a season.

When planted in the ground, lettuce requires a fair amount of water, as well as a good deal of garden space. Fortunately, lettuce can be grown in containers, which conserves resources and helps to protect the tender leaves from pests patrolling the garden for a tasty meal.

Growing lettuce in containers is a straightforward and simple process that makes tending to and harvesting your crop a cinch. Let’s talk about what it takes to grow a bountiful harvest of crisp, refreshing lettuce as container plants.

First, Choose The Right Variety

There are many different types of lettuce to choose from, from iceberg, to romaine, butterhead, looseleaf, and mesclun. Different types of lettuce have different flavors, and each brings its own texture and flavor to the salad bowl.

The nice thing about planting lettuce in containers is that there is no reason not to plant a variety of different types. I love a beautiful salad made with a combination of lettuces, each with its own shade and texture. Each type of lettuce has a perfect place in terms of culinary use, so why not cover all the bases?

If you’re fond of lettuce on your sandwiches, I highly recommend growing some romaine or butterhead, as these types are flavorful and have sturdy leaves. Iceberg has a nice crunch that is a wonderful salad foundation, but sometimes it can be a bit crumbly when faced with a hamburger bun.

Mesclun is visually beautiful, colorful mixed greens that can have an herbaceous quality and are a delicate and delicious garnish tossed in a mild vinaigrette.

Think Vertical

It’s perfectly acceptable to grow lettuce in just about any container you desire, but I personally love these vertical planters from GreenStalk for growing my greens. All of those beautiful leafy greens look extra lovely against the Terracotta color, and the footprint is tiny compared with the yield you can produce. One 5-tier planter can hold 30 plants!

In addition to the space-saving benefit of a vertical planter, it also makes harvesting much less laborious. I don’t know a single gardener that doesn’t love a time and energy saver in the garden. Vertical planters are easy to rotate and move around to find just the right light as well.

The only exception to vertical planting is in growing iceberg lettuce. Those crunchy heads don’t quite fit in a vertical planter. For icebergs, I recommend a short, wide container. Iceberg lettuce has a shallow root system but needs a fair amount of surface area.

Choose the Right Soil

Most vegetables like nitrogen-rich soil, and lettuce, being a leafy vegetable, is certainly no exception. Nitrogen helps lettuce plants to produce more foliage, which means a more bountiful harvest for you.

The ideal soil type for growing lettuce is rich in organic matter and well-draining but moist. You don’t want your lettuce sitting in soggy soil, so be certain that there is adequate drainage in your containers and that your soil doesn’t compact easily. This is especially true for heading-type lettuces.

Start with a high-quality raised bed or standard potting soil. You can grow your lettuce in this alone, but if you want to give it a robust start, consider adding some compost into the mix.

Working a few inches of good, rich compost into the top several inches of soil will provide your lettuce plants with that much-needed nitrogen, and it will cut down on your fertilizer bill as well.

Sow Seeds Properly

Lettuce seeds can be directly sown into the container you are growing them in. These little seeds germinate and grow very quickly. Under the right conditions, these seeds can germinate in as little as two days, but the average time is more like 4-10 days.  Soaking your seeds overnight will jumpstart the germination process.

If you are growing multiple plants in one container, space them out about 8”; thin leaf types only need about half this amount of space. Use your finger or the eraser end of a pencil to make a very shallow divot in the soil, and drop a pinch of seeds into each divot. Lightly cover the seeds with loose soil. Ideally, most lettuce seeds are planted no deeper than 1/8″, so you barely need to cover the seeds.

Find the Right Light

Lettuce is a cool-weather crop; some types are rather delicate and do not tolerate much heat. Ideally, most types of lettuce thrive in an exposure condition where they receive 5 or 6 hours of sun in the morning and light shade in the afternoon.

The afternoon sun can be a bit harsh and dehydrating. If your leaves look wilted, try giving your lettuce a bit more shade. The great thing about container planting is that it is much easier to correct a location issue.

Timing is Everything

When we say that lettuce is a cool weather crop, we mean that the best times for growing it are in the spring and fall months. Lettuce seeds germinate faster in cooler weather.

You want to avoid planting before the last frost has passed, as this can damage young seedlings. The ideal temperature range for growing lettuce is 45°-80°.

Because we are planting in containers, it doesn’t matter if the ground is frozen. Young lettuce plants will need protection if you are planting in spring and there is a chance of freezing weather. If you are planting in the fall, wait until the hottest days of summer have passed and daily highs aren’t surpassing that 80° mark.

Water Generously

Because lettuce plants have shallow roots, they need to be watered frequently. Check the soil regularly, and don’t allow it to dry out completely. When the top inch of soil is dry, it’s time to water. This typically ends up being about twice a week, but it can be more for lettuce planted in containers.

Underwatering will cause your seedlings to fail or your seeds not to germinate.

As much as underwatering will cause your lettuce to suffer, so too will overwatering. Because of their tightly clustered foliage, lettuces are prone to fungal and bacterial rot.

This is usually the result of wet soil, which can make the plant more susceptible to fungal infection. Ensuring that your soil is not compacted and your container has adequate drainage are great ways to prevent overwatering.

Feed Your Food

Lettuce should be fertilized regularly. Fertilizing serves more than one purpose for lettuce. The most obvious is that fertilizer will create more robust, faster-growing plants.

In the case of lettuce plants, fertilizer also improves the flavor of the vegetable, cutting down on bitterness.

Fertilize your lettuce plants every two weeks using liquid or granular fertilizer applied to the soil. Fish emulsion makes an excellent fertilizer for lettuce plants; its nitrogen-heavy ratio of 5-1-1 gives lettuce what it needs to produce sturdy leaves.

Alternative fertilizers for lettuce include alfalfa meal, blood meal, or feather meal, all of which have high nitrogen. These must break down in the soil before they become plant-available, so with these, it’s recommended to start from the time of planting and stay consistent with your application regimen. Lightly work these into the soil’s surface when you side-dress, and water them in well.

Protect it from Predators

Lettuce is susceptible to a number of garden pests. Possibly the most damaging are snails and slugs. Creating a barrier around your plants is the most effective way to ward off these slimy gastropods. Copper tape can act as a barrier to keep these critters off of your lettuce plants. The copper disrupts the function of cells in the skin of the snail or slug and ultimately kills them.

Beer traps are another great way to deal with our slimy visitors. A beer trap is a shallow bowl or pie pan filled with flat beer, placed with the rim at the soil level. Slugs and snails are attracted to the smell of yeast, so the beer lures them into the trap, where they consume more beer than they can handle and ultimately drown.

There are also organic slug and snail baits that are formed into pellets. These cause no harm to us or our gardens, but snails and slugs who eat them will die off.

Harvesting at The Right Time

If you want a full head of a heading lettuce variety, you’ll need to wait until that variety comes to maturity before you harvest.

Wait until the heads are mature and look nice and plump before harvesting for the best flavor. Maturity typically takes 70-80 days for these varieties.  Slice the head off right at the surface of the soil, and you have a beautiful head!

Loose leaf lettuces are different and a great option if you want to have a longer period of time to harvest and enjoy your crop. These varieties mature faster. Some mature in as little as 30 days from germination, and many types of loose leaf lettuces will be harvestable.

The great thing about these plants is that you can continue to allow them to grow and harvest repeatedly throughout the season. You should be able to harvest 3 or 4 times in a season from one plant by using the cut-and-come-again method. In this method, you select a few of the outer, more developed leaves per plant and cut them off at the base of the plant, leaving the inner rosette to continue to develop. This also works for heading varieties if you only need a few leaves!

After the third or fourth harvest of loose-leaf lettuces or the second harvest of heading lettuces using the cut-and-come-again method, newer leaves will have a slightly more bitter flavor. Taste a leaf and decide if it’s time to harvest the full head and replace it with a newer, younger plant for sustained harvesting.

Final Thoughts

Lettuce can be a very productive and healthy crop when grown in containers. Container growing has plenty of advantages, especially with space-saving vertical planters. Keep a few things in mind when planting and caring for your crop, and you will be practically rolling in lettuce in no time.

• Choose one variety or several if you want a beautiful mixture of lettuces.
• Consider vertical planting for loose leaf types, romaine, and butterhead.
• Use rich, well-draining soil, and make sure your containers have adequate drainage.
• Plant when the weather is mild, not hot.
• Water as soon as the surface of the soil is dry.
• Give your lettuce plenty of nitrogen-rich fertilizer.
• Combat snails and slugs with copper, beer, or organic slug and snail baits.