How to Grow Lettuce in a Small Greenhouse With Container Setup

There can be several reasons for growing lettuce in a greenhouse, including disease issues due to environmental factors, extreme heat or cold in outdoor conditions, and the desire for a year-round harvest.

And if you are also thinking of growing lettuce in a small greenhouse for the above reasons, you are at the right place! Here, we will guide you in building a small greenhouse with container gardening to grow fresh and crispy lettuce at home.

There’s something so delicious about homemade salads made with fresh lettuce! Not only does this vegetable taste great, but it’s also easy to grow. Especially if you grow it in a greenhouse, you can enjoy fresh, green lettuce all year round, protected from changing weather, pests, disease issues, and other environmental factors that affect lettuce growth.

Lettuce is a winter crop with a refreshing and crispy taste, depending on the variety. It thrives best in chilly conditions, ideally between 15 to 18C, making it easy to grow lettuce in a greenhouse for budget-conscious gardeners.

Do you Know? This leafy vegetable consists of several varieties with unique tastes such as iceberg, winter density, Romain, butterhead, and batavia. It is not only mouthwatering but also provides many health benefits with its nutrients including vitamins A, C, K, folate, potassium, and iron.

Lettuce is also widely used by food companies, chefs, restaurants, and cafes. It is added to salads, sandwiches, and burgers as a fresh and crunchy ingredient and is often used to decorate dishes.  

The journey of growing lettuce in a greenhouse is opportune to achieve weather protection, better water management, the taste of freshness, and more yield in an environmentally friendly way.

Let’s find all the steps to grow lettuce in a small greenhouse before understanding suited lettuce varieties that can be grown in winter in a greenhouse.

General Content (Growing Lettuce Indoors and Outdoors)👇

If you’re looking for a complete guide on growing lettuce both indoors and outdoors, we’ve covered everything you need to know to achieve the best results here.

The Most Popular Lettuce Varieties Suitable for Winter Cultivation in Greenhouses

Since you have to maintain a controlled environment according to the chosen lettuce variety, selecting the right variety is still vital for the following reasons;

1. Choosing the right variety helps in getting higher yields.
2. The taste and texture of different varieties are crucial for use in different dishes.
3. Some varieties grow better in certain seasons.
4. Some varieties are more resistant to diseases.

In terms of taste, you can choose a variety according to your preference, but some specific varieties are recommended for high yields, good growth, weather conditions, and disease resistance.

Loose-leaf lettuce

1-Baby Oak Leaf: This soft and flexible leaf variety works best in a greenhouse, especially in cold climates, and provides you with a continuous supply of leaves, allowing you to harvest repeatedly.

2-Black-Seeded Simpson: It is a loose-leaf variety, that grows very quickly, is relatively resistant to diseases, and does best in a greenhouse, where you can get a constant supply of fresh leaves.

3-Salanova: It is a high-yielding and versatile variety, producing both baby leaves and full heads. Salanovo has several different varieties, which perform superbly well in the greenhouse and give you a continuous harvest in a single season.

Butterhead lettuce

Tom Thumb: This compact and small lettuce type can be easily grown in small greenhouses or containers and produces optimal yields in very little space in the shape of soft leaves with a slight bitterness.

Winter Marvel: This variety also grows in low light and is perfect for an unheated greenhouse. Winter Marvel can grow in cold weather and does well in low-light environments.

Arctic King: It is a cold-tolerant lettuce, which can grow even in low temperatures., especially good for growing in greenhouses in cold climates, where it produces good yields despite the cold.

Bibb lettuce: It is a small, compact head of lettuce with a buttery flavor, is optimal for early-season harvest, and grows well, especially in cold weather.

Romaine lettuce

Monte Carlo: It is a compact romaine lettuce, perfect for small greenhouses as its crunchy and crispy leaves are less affected by weather changes, and it has fewer flowers that do not form flowers in the middle.  

Little Gem Lettuce: Little Gem lettuce is small, sweet, and tender with buttery leaves. It provides continuous, quick harvests and is perfect for compact spaces.

Batavia lettuce

Dorian: It is a Batavia type of lettuce with good disease resistance. Its leaves are beautiful, open, and soft. The Durian variety is the most disease-resistant and grows very well in a greenhouse.

Information for You! When you are growing lettuce varieties in a greenhouse, each variety has its own specific temperature requirements.

Although we generally refer to a moderate temperature that is suitable for most varieties, the temperature tolerance of each variety can vary.

For example, loose-leaf varieties like “Baby Oak Leaf” and “Tom Thumb” require moderate temperatures between 15C and 20C, and cold-tolerant varieties like “Arctic King” and “Winter Marvel” have a higher tolerance to cold. In addition, varieties like “Salanovo” and “Durian” also do well in warmer conditions.

Required Factor	Conditions
Temperature	15°C to 20°C (59°F to 68°F); Bolting can occur at 24°C (75°F) and below 0°C is unsuitable
Sunlight	Partial sunlight, 4-6 hours daily
Soil	Loose, well-draining, with a pH of 6.0 to 7.0
Watering	Keep the soil moist, but avoid waterlogging
Humidity	50% to 70% relative humidity

How to Grow Lettuce in a Small Greenhouse: Setting Up a Greenhouse with a Container

Do you want to grow lettuce at home? So, you can have two options: buy a ready-made greenhouse or build one yourself. In this section, I will focus on the DIY method to build an effective small greenhouse for your lettuce, saving money and customizing it according to your space and requirements.

Do you Know? Lettuce can be grown directly in greenhouse soil, especially for larger farming setups. However, container gardening is more effective for gardeners with limited space.

Steps on Growing Lettuce In A Small Greenhouse In A Container

With a small greenhouse or container gardening, you can grow lettuce in any part of your home, such as your balcony or terrace. You can set up your greenhouse in a small container, for which you will only need a plastic sheet to cover your container. It can maintain the temperature and humidity inside the greenhouse, allowing for optimal lettuce growth.

Step #1: Choose The Right Container According to Lettuce variety

Choosing the appropriate container for lettuce depends on your desired growth. For smaller plants, 6-inch or 8-inch deep containers are best, while for larger varieties such as Romain lettuce, 12-inch or deeper containers can work, allowing the plant’s roots to spread freely and grow better. In addition, the container should have good drainage so that overwatering does not damage the lettuce.

Do you Know? You can also use seedling trays that automatically retain moisture, but you must have to transplant them into a larger container or the ground after seedling. However, if your chosen container is small and does not meet to lettuce size, here also, you may also need to transplant.

Variety	Harvesting Size	Container Size (Dimensions)
Loose-leaf Lettuce	3-4 inches	6-8 inches (diameter), 4-6 inches deep
Butterhead Lettuce	6-8 inches	8-10 inches (diameter), 6-8 inches deep
Romaine Lettuce	6-12 inches	10-12 inches (diameter), 8-10 inches deep
Baby Leaves (Batavia)	3-6 inches	6-8 inches (diameter), 4-6 inches deep

Step #2: Preparing the Soil for Lettuce

Make the soil completely pure by removing all debris and waste. Lettuce prefers well-drainage, fertile soil with 6.0 to 7.0 pH. So if the soil is too salty or too acidic, the pH may be low, while soft, sandy soil usually has a suitable pH.

If you are in doubt, you may need to raise or lower the pH;

• Low pH 5.5<: Soil can be acidic for lettuce growth. Use chalk or Ag lime. Here’s find out how Ag lime is good to increase its pH level.
• High pH 7.5>: Soil can be more alkaline. Use sulfur, compost, peat moss, or acidic fertilizer to decrease its pH level.

On the other hand, nitrogen, phosphorus, and potassium are essential for early lettuce growth. Add compost, worm castings, or peat moss if the soil is hard or lifeless. But if the little worms are happily crawling around, the soil is fertile! 🤭

After preparing the soil, pour it into the container and press it well. Avoid pressing it so hard that it becomes tough, preventing air circulation in the soil.

Choose Reliable Lettuce Seeds & Sow Them Properly

Depending on the variety, lettuce seeds are tiny. When sowing them, you may find it helpful to choose pelleted seeds because they have a protective coating that improves their germination rate.

What are pelleted seeds? Pelleted seeds are seeds coated with a protective layer, often clay, to aid in handling and planting. These seeds are typically left to dry for 4-5 days after coating before use.

You can sow these seeds in rows 8 to 16 inches apart, and if you need more space, you can sow them 12 inches apart to create proper spacing. If you spread the seeds out too much, thin them out later. Plant the seeds 1/4 inch deep to allow them to germinate effectively and maintain better air circulation between your plants.  

If seeds are popping out, here’s discover the worm’s role in fertilizing the soil.

So at this point, we have a container ready in which we have sown lettuce seeds. If you want to grow more, you can make additional containers like this. Now we need a greenhouse that will fit our prepared container so that we can keep it in a controlled environment.

We are providing this information only to help you understand the different options. You can look at a ready-made greenhouse from IKEA as an option, but you can also search for other brands on Google according to your preferences and budget.

Build your own Mini Greenhouse for Lettuce: Short Steps and Complete Video.

Materials List for Mini Greenhouse

• Clear plastic panels – Double-walled, used for insulation and covering.
• Wooden planks (1×2 lumber) – Used for framing the structure.
• Screws – Needed to secure the frame and attach panels.
• Tape – Used for temporary hinges and sealing edges.
• Drill – Required to make holes and assemble the frame.
• Saw – Used to cut wooden planks and plastic panels.
• Measuring tape – Ensures precise measurements for accurate cuts.
• String or rope – Used to secure doors and allow ventilation control.
• Sandpaper – Helps smooth the wood edges for a clean finish.
• Hinges (optional) – Can be used for a more durable roof attachment.

Step-by-Step Process to Build the Small Greenhouse For Lettuce

1. Plan the greenhouse size and design.
2. Cut the plastic panels in advance.
3. Build and assemble the wooden frame.
4. Create the base frame and attach the upright supports.
5. Add the top shelf and bottom support.
6. Install and secure the side panels.
7. Attach the roof frame and plastic panels.
8. Create ventilation openings and handles.
9. Secure the greenhouse with screws for easy disassembly.
10. Place your lettuce seedlings trays or containers inside and enjoy gardening.

For a complete guide, watch the full video by What’s In The Garden channel on Youtube: [Video Link]

Have you prepared your greenhouse or have you ordered it online or do you have it ready? In all three situations, now you have both available. One is a container or seedling tray in which lettuce seeds were sown, and second is the greenhouse! Now we have to place the container or seedling tray that you had prepared safely in the greenhouse. Now, the question is, what is the ideal environment for lettuce to maintain in the greenhouse. Let’s understand now.

Creating the Ideal Environment for Lettuce Growth in Your Greenhouse (Winter & Summer Tips)

Keep the temperature in the greenhouse between 55°F and 70°F during the day, but if the temperature reaches 85°F on hot days, immediately use a ventilation system to lower it or put a damp cloth on the soil to keep it cool. If the temperature drops below 40°F at night, use additional heaters to protect the plants from the cold.

In terms of lighting, if you lack natural sunlight, install a good-grade grow light in the greenhouse that provides 5 hours of direct light. It will improve the growth and color of the plants.

Regarding soil, lettuce likes soil that is well-drained and retains moisture. To do this, add coco coir or peat moss to the top of the soil to increase its water-holding capacity, but also make sure that the soil pH remains between 6.5 and 7.0 so that the plants can grow at their best.

Handling Common Problems During Lettuce Growth in the Greenhouse

Root Rot: Root rot can quickly develop if the soil remains too wet for extended periods. Lettuce, especially in a greenhouse, can be highly sensitive to overwatering. Ensure your greenhouse has proper drainage, and check the soil moisture regularly to avoid sogginess.

Yellowing or Wilting Leaves: Excessive watering or poor air circulation can lead to wilted or yellow leaves. Make sure your greenhouse has adequate ventilation, especially during warm days. This helps in maintaining a good airflow and prevents mold or fungus from taking over.

Leaf Bitterness: Lettuce can turn bitter and tough when exposed to high temperatures for too long. During summer, ensure the temperature stays below 75°F, and use a shading cloth when it gets too hot. Regularly harvest leaves that are fully grown but still tender.

Bolting: As temperatures rise, lettuce tends to bolt or go to seed. This drastically affects taste and quality. Use shade cloth or keep the greenhouse cool in the summer to delay this process and keep your lettuce producing longer.

Pests Alerts: Your greenhouse lettuce can get attacked by pests like aphids, earwigs, and cutworms. Plus, pesky woodchucks and rabbits might try to sneak in for a snack! Keep your greenhouse doors and windows tightly shut to stop them from getting in and causing damage.

Beyond the above problems, here discover 10 hidden reasons why your plants aren’t thriving.

Best Companion Plants for Lettuce: Boost Growth and Protect Your Crop

When growing lettuce, choosing the right companion plants can make a huge difference. Garlic is a top choice, as it repels aphids and other harmful insects. If you’re wondering how to grow garlic, check out our complete guide here.

Radishes are another great option, helping to keep slugs and snails away while also growing quickly and not competing too much with lettuce.

Marigolds offer natural pest control by emitting a strong scent that deters harmful insects. Basil can attract beneficial insects and even improve the flavor of your lettuce. Other companions like onions and chives can also help ward off pests while adding extra flavor to your meals.

Harvesting Lettuce

Harvest your lettuce when the leaves are fully grown but still tender, typically 5-8 weeks after planting. For leaf types, you can pick the outer leaves first. For head lettuce, wait until the head feels firm but not tight. Avoid leaving it too long, as leaves may become bitter. Harvest in the morning, and use sharp scissors to prevent damaging the plant.

Growing Lettuce in North Carolina: UK👇

North Carolina’s climate presents unique challenges for growing lettuce, but with the right techniques, you can still get a great harvest. Check out our detailed guide for region-specific tips here.

Growing Lettuce in Florida: UK👇

or those in warm, humid areas like Florida, growing lettuce can require special care. We’ve communicated key strategies to help you keep your lettuce fresh and healthy in hot climates here.

Frequently Asked Questions: Growing Lettuce in a Greenhouse