How To Grow Crops in a Greenhouse: The Ultimate Guide

Growing crops in a greenhouse is an excellent way to get a jump on the growing season and extend your harvest well into the winter months. The controlled environment allows you to manipulate the temperature, humidity, and amount of sunlight your plants receive, giving you greater control over the growth and development of your plants.

To grow crops in a greenhouse, you must purchase a greenhouse kit, assemble the frame, and install the glazing. You will also need to prepare the foundation and flooring, install vents and fans, and set up a watering and drainage system. Once assembled, you can begin planting your crops.

If you’re looking for a way to increase your yield and grow healthy, bountiful crops all year long, read on for the ultimate guide to growing crops in a greenhouse. In the following sections, I’ll discuss everything you need to know about greenhouses, including types, benefits, essentials of a greenhouse, and what crops to grow. Buckle up for a crash course in greenhouse gardening!

What Is a Greenhouse?

Before I get into the nitty-gritty of how to grow crops in a greenhouse, let’s first discuss what a greenhouse is. A greenhouse is a structure made of transparent material, such as glass or plastic, used to grow plants in a controlled environment. Greenhouses can be small enough to fit on a windowsill or large enough to cover an acre of land.

The most essential function of a greenhouse is to trap heat from the sun and create a warm, humid environment for plants to grow in. This is accomplished by the greenhouse effect, which occurs when the sun’s rays pass through the transparent material and are converted into heat. The heat is then trapped inside the greenhouse, creating a warm environment for plants to grow in.

Unlike the outside garden, which is subject to the changing seasons and weather conditions, the greenhouse environment is relatively stable, allowing plants to grow year-round. This is why greenhouses are often used to grow crops that are out of season or would not survive in the cold weather, such as tomatoes, cucumbers, and peppers.

Greenhouses can be used for various purposes, such as starting seedlings, overwintering plants, and growing fruits and vegetables. They can be simple structures made from recycled materials or elaborate buildings with climate control and automated systems. No matter the size or purpose, all greenhouses serve the same function of providing a protected environment for plants to grow in.

Types of Greenhouses

Greenhouses come in various shapes and sizes, each with its benefits and drawbacks. The type of greenhouse you choose will depend on your specific needs, space constraints, budget, and the type of plants you want to grow.

Understanding the different types of greenhouses will help you choose the right one for your needs. However, before I discuss the common types of greenhouses, let’s first explore the different materials they are made from. Most greenhouses’ rudimentary frames are made of wood, metal, or PVC piping.

Wood: With its excellent insulating properties and classic rustic look, wood is a popular choice for greenhouse frames, especially in cold climates. However, it is also the most expensive option and requires regular maintenance to prevent rot and decay.
Metal: Metal frames are strong and durable, making them ideal for larger greenhouses. They are available in aluminum or steel, with aluminum being the more popular choice due to its lighter weight and resistance to rust. Their high upfront cost is offset by their longevity, making them an excellent long-term investment.
PVC: PVC piping is lightweight, strong, and easy to work with, making it a popular choice for do-it-yourselfers. It is also the most affordable option, making it a good choice for those on a budget. Unfortunately, it lacks the rigidity of wood and metal frames, making it less ideal for larger greenhouses. PVC can also deteriorate in the sun due to UV rays, so it is crucial to choose a UV-resistant variety if you decide to go this route.

Once the framework is in place, the next step is to cover it with a transparent material. The covering is what makes a greenhouse what it is, as it is this material that traps heat from the sun and creates the warm, humid environment plants need to grow. The most common choices are glass, acrylic, polycarbonate, or fiberglass.

Glass is the classic choice for greenhouse coverings due to its clarity, durability, and ability to trap heat. It has excellent insulation properties, is aesthetically pleasing, and provides an unobstructed view of the plants inside. However, it is also the most expensive option and most challenging to work with. It cracks easily and isn’t easily bent or shaped, making it difficult to work with for DIY projects.
Acrylic is a lightweight alternative to glass that is just as clear and durable. It is easily bent and molded, making it much easier to work with than glass. However, it’s expensive and can yellow and degrade in the sun over time.
Polycarbonate is a clear, lightweight plastic available in sheets or panels. It is a budget-friendly option compared to acrylic and glass and is much easier to work with. However, it can become brittle and break over time in the sun. It also tends to diffuse sunlight, reducing the amount of light that reaches the plants.
Fiberglass is the least expensive option and is easy to work with, making it a popular choice for DIY greenhouses. It holds extremely well in extreme climates and can be UV-coated to extend its lifespan. However, it deteriorates with time and can turn yellow, reducing light transmission.

With that out of the way, let’s look at some of the most common types of greenhouses. They include:

Lean-to
Gable-style
Ridge and furrow
A-frame
Hoophouse
Geodesic dome
Gothic arch
Uneven span

I will discuss each one in more detail below.

1. Lean-To

As the name suggests, a lean-to greenhouse leans against another structure, such as a house or shed. They are the most basic and simplest type of greenhouse and are the easiest to build. They use the existing structure of one or more walls, which reduces the amount of material and labor required.

Their roof is extended out from the wall of the existing structure, usually at a slight angle, to allow rain and snow to run off. Their length can extend as far as the existing structure and should face the direction with the best exposure to sunlight. Due to the constrained space, lean-to greenhouses are typically smaller and limited to single or double-row planting.

2. Gable-Style

A gable-style greenhouse is the most popular type and is what most people think of when they picture a greenhouse. It is a free-standing structure with a peaked roof, and its walls are typically made of glass or polycarbonate panels.

The gable-style greenhouse is one of the easiest to build, as the walls and roof can be made from a kit. They come in several sizes, making them suitable for small and large gardens. Gable-style greenhouses provide plenty of room inside and offer good exposure to sunlight.

3. Ridge and Furrow

Ridge and furrow greenhouses are similar to gable-style greenhouses but have a series of ridges and furrows running along the length of the roof.

This type of greenhouse is more common in commercial operations as it offers a higher level of light transmission and ventilation. Water and melted snow run off along the length of the furrows, making them ideal for locations that receive a lot of snowfall.

4. A-Frame

Similar to a gable-style greenhouse, an A-frame greenhouse has a peaked roof. However, its walls are sloped downwards towards the base, making it more aerodynamic and stable in high winds.

They are easy to build and are typically made from wood or metal framing covered with polycarbonate or glass panels. A-frame greenhouses are a good choice for gardeners who want plenty of headroom to work in.

5. Hoop House

A hoop house is a type of greenhouse constructed from a series of metal or PVC pipes bent into an arch shape. The ends of the pipes are buried in the ground, and the hoops are covered with a layer of polycarbonate film, which creates a barrier against the elements.

Hoop houses can be any size and shape but are typically used for small-scale commercial operations. They are ideal for protecting long rows of crops from the elements.

6. Geodesic Dome

A geodesic dome greenhouse features a series of triangular panels arranged in a pattern that forms a spherical or hemispherical shape. The panels are typically made from metal or PVC piping and are covered with a layer of polycarbonate film or glass.

Geodesic dome greenhouses are strong and stable and can be adapted to any size or shape. They hold up well in severe weather conditions, making them ideal for locations that experience high winds or heavy snowfall. You can purchase a kit to build a geodesic dome greenhouse or craft your own by mass-producing rods or sticks and assembling them into the desired shape with connectors.

7. Gothic Arch

If you’re a fan of gothic architecture, a gothic arch greenhouse is a perfect way to add a touch of elegance to your garden. Gothic arch greenhouses feature a series of pointed arches that support the roof.

This eliminates the need for trusses and provides more headroom than other greenhouse designs. Gothic arch greenhouses are available in various sizes and can be small enough to fit on a patio or large enough to accommodate commercial operations.

8. Uneven Span

An uneven span greenhouse makes for the most efficient design if you have a sloped or uneven piece of land. One of its roofs is longer to allow more sunlight intake, while the other is shorter to provide more stability. The longer side is usually south-facing to get the most sunlight.

Benefits of Growing Crops in a Greenhouse

Today, there are over 8,750 greenhouse vegetable gardens in the United States, and the number is steadily increasing as the population increases and technology advances. Small-scale and commercial farmers are turning to greenhouses to grow their crops year-round, regardless of the weather conditions. Here are some of the benefits of growing crops in a greenhouse:

1. Controlled Environment

One of the most significant benefits of growing crops in a greenhouse is the ability to control the environment. As a farmer, you know how frustrating it is to have your crops ruined by a sudden hailstorm or heatwave. Extreme weather conditions can destroy an entire crop in hours, leaving you with nothing to show for all your hard work.

The key to healthy, bountiful yield is providing your crops with consistent conditions conducive to growth. Greenhouses allow you to maintain a controlled environment by regulating temperature, humidity, ventilation, and irrigation. They create a barrier between your plants and the outside world, protecting them from unexpected weather events.

2. Extended Growing Season

Due to the controlled environment, greenhouse crops can be grown year-round instead of seasonally. As the weather outside changes, you can adjust the temperature and humidity inside the greenhouse to ensure your plants continue to thrive.

This means you can have a steady supply of fresh fruits and vegetables all year long, even in the middle of winter! However, you must have the necessary technology to create the ideal conditions for each type of crop.

Not only does an extended growing season provide you with a consistent supply of fresh produce, but it also allows you to take advantage of peak prices. By growing crops year-round, you can sell them when the demand is high, and the price is right. This can be a significant advantage for farmers trying to maximize their profits.

3. Higher Quality Crops and Improved Yields

Quality is essential when it comes to selling your crops. Consumers are willing to pay a premium for fresh, high-quality produce, and greenhouse-grown fruits and vegetables fit the bill. Thanks to the controlled environment, greenhouse crops are typically larger, healthier, and more aesthetically pleasing than their outdoor counterparts.

What’s more, because you can regulate the conditions inside a greenhouse, you can optimize growth and yield. Since the crops are grown in ideal conditions, they are more likely to reach their full potential, resulting in a higher yield.

4. Reduced Pest and Disease Pressure

Pests and diseases are a constant threat to any farmer, as they can quickly destroy entire crops. One of the benefits of growing crops in a greenhouse is the reduced risk of pest infestations and diseases.

The controlled environment makes it difficult for pests and diseases to spread, as they are typically introduced from the outside. Access to the greenhouse is also restricted to a few people, reducing the risk of pests and diseases.

Additionally, because you can closely monitor the conditions inside a greenhouse, it’s easier to spot problems early on before they become too severe. This allows you to take action quickly and prevent widespread damage. You can also introduce beneficial insects to the greenhouse, such as ladybugs, which help control pests.

5. Increased Sustainability and Energy Efficiency

Greenhouses are typically more sustainable and energy-efficient than traditional farming operations. Because the controlled environment reduces the need for harmful pesticides, herbicides, and other chemicals, it has a lower environmental impact. Additionally, greenhouses can be outfitted with solar panels to generate electricity, reducing their environmental footprint.

In terms of energy efficiency, greenhouses use less energy to maintain the ideal conditions for plant growth. For example, in a cold climate, a greenhouse can be designed to trap heat from the sun, which reduces the need for artificial heating. This can lead to significant energy savings over time and reduce your carbon footprint.

Cons of Growing Crops in a Greenhouse

While there are many benefits to growing crops in a greenhouse, there are also some drawbacks.

1. High Initial Investment

One of the most significant drawbacks of greenhouse farming is the high initial investment. Greenhouses can be expensive to construct and require a lot of energy to operate. This can make it difficult for small farmers to get started with greenhouse farming.

However, the high initial investment can be offset by the many benefits of greenhouse farming, such as the increased yield and reduced pest and disease pressure. Additionally, government incentives are often available to farmers who want to build a greenhouse. These incentives can help offset the cost of construction and make greenhouse farming more affordable.

2. Operating a Greenhouse Can Be Challenging

Without the proper experience, operating a greenhouse can be challenging. Maintaining the ideal conditions for plant growth requires a lot of knowledge and expertise. This can be difficult for farmers who are new to greenhouse farming.

To maximize the benefits of greenhouse farming, partnering with a knowledgeable and experienced greenhouse operator is crucial. If you are doing small-scale production, you can also take greenhouse classes offered by agricultural extension services.

Additionally, greenhouses require a lot of maintenance. The controlled environment is susceptible to drastic changes, which can damage or kill plants. For example, if the temperature gets too hot, the plants can be damaged. If the humidity is too high, it can create an ideal environment for mold and mildew to grow.

For this reason, greenhouses need to be monitored closely to ensure that the conditions are suitable for plant growth.

Despite the challenges, greenhouse farming can significantly improve your yield, reduce pest and disease pressure, and increase your sustainability. With the proper knowledge and expertise, greenhouse farming can be a profitable and rewarding endeavor.

How To Choose the Right Greenhouse for Your Needs

One critical step to starting a greenhouse operation is selecting the correct type of greenhouse for your needs. Choosing the right greenhouse will depend on several factors, including:

The type of crops you want to grow
The climate you live in
The size of your operation
Your budget

Let’s take a closer look at each of these factors:

1. The Type of Crops You Want To Grow

To determine the type of greenhouse you need, you first must select the crops you want to grow. Greenhouses are available in a variety of sizes, shapes, and materials. Some are better suited for certain crops than others. Additionally, crops have varying growing conditions, so it’s essential to choose a greenhouse that can accommodate the specific needs of your plants.

Some crops, such as tomatoes, require a lot of sunlight. In this case, you’ll need a greenhouse with many south-facing windows. Other crops, such as cucumbers, don’t need as much sunlight. For these plants, you can choose a greenhouse that has fewer windows.

Additionally, some crops require a lot of space to grow due to their growing design. Sprawling crops need a lot of room to spread out, while vertical crops need a tall ceiling for adequate headroom. Be sure to consider the space requirements of your plants when selecting a greenhouse.

2. The Climate You Live In

What is your local climate like? Do you live in an area with extreme weather conditions, such as high winds or heavy snowfall? If so, you’ll need to choose a greenhouse that can withstand these conditions.

Areas with harsh winters require a greenhouse that can be easily heated to keep the plants warm. Likewise, areas with high winds need a sturdier greenhouse that can withstand strong gusts.

Additionally, you’ll need to consider your area’s average temperature and humidity levels. If you live in a hot and humid climate, you’ll need a greenhouse with good ventilation to keep the plants cool. Conversely, if you live in a cold and dry environment, you’ll need a greenhouse that can retain heat and moisture.

3. The Size of Your Operation

How large is your greenhouse operation? Are you growing crops for personal use or running a commercial operation? For hobbyists and small-scale growers, a small greenhouse is typically all that’s needed. You can easily DIY a small greenhouse using a kit or plans.

However, you’ll need a much larger greenhouse if you’re running a commercial operation. In this case, you’ll need to work with a commercial greenhouse manufacturer to build a custom structure. Select a manufacturer who has experience building greenhouses to your specific needs to avoid any issues.

4. Your Budget

This goes without saying, but your budget will be a significant factor in the type of greenhouse you choose. Greenhouses can range in price from a few hundred dollars to tens of thousands of dollars depending on the size, features, and materials.

It’s important to remember that you don’t need the most expensive greenhouse to be successful. In fact, many hobbyists and small-scale growers get by just fine with a basic and inexpensive structure.

If you’re running a commercial operation, you’ll need to invest in a higher-quality greenhouse that can accommodate your needs. Working within your budget will help you choose the best greenhouse for your specific needs without breaking the bank.

Essentials for Growing Crops in a Greenhouse

Having understood the basics of what to look for while zeroing in on a greenhouse, we can now focus on the essentials necessary for successfully growing crops. No matter what type of greenhouse you have or what crops you’re growing, there are certain essentials that every operation needs.

Ventilation

Like a house, a greenhouse needs proper ventilation to function properly. Ventilation helps regulate the temperature and humidity levels inside the structure, which is crucial for the health of your plants.

There are two types of ventilation that you’ll need to consider: natural and mechanical.

Natural ventilation is when the hot air inside the greenhouse rises and escapes through vents in the upper part of the structure. This is a passive ventilation system that doesn’t require any type of fan or other mechanical systems.
Mechanical ventilation, on the other hand, uses fans to actively move the air inside the greenhouse. This is a more expensive option, but it’s often necessary in larger greenhouses or in cases where the natural ventilation isn’t adequate.

Lighting

Plants need light to grow, so it’s vital that your greenhouse is equipped with an adequate lighting system. The light helps the plants to photosynthesize and produce the food they need to grow. Unlike in an outside setting that relies on the sun, greenhouses need to have an artificial lighting system in place.

Two types of lighting are commonly used in greenhouses: fluorescent and HID (high-intensity discharge). Fluorescent lighting is less expensive but doesn’t produce as much light as HID lighting. It’s typically used in smaller greenhouses or for starting seedlings.

HID lighting is the most efficient option, and it produces a lot of light, making it ideal for larger greenhouses. However, it’s also the most expensive option. The most common HIDs include:

High-pressure sodium (HPS) lamps: They are the most common due to their high efficiency, long bulb life, and wide availability.
Metal halide (MH) lamps: They produce a whiter light than HPS lamps, making them ideal for plants that require more blue light, such as lettuce and other leafy greens.
LED (light-emitting diode) lamps: They are the most energy-efficient option and can last up to 50,000 hours. They are relatively affordable and are becoming more popular in greenhouses.

Heating

During winter, the temperature inside a greenhouse can drop significantly, which can be harmful (or even fatal) to your plants. That’s why you need to have a heating system in place to keep the temperature at a consistent level.

There are several types of heaters you can use in a greenhouse, including:

Electric heaters: They are one of the most popular options because they’re relatively affordable and easy to use. However, they can be a fire hazard when misused. Common electric heaters include radiant heaters, panel heaters, and ceramic heaters.
Gas heaters: Unlike electric heaters, gas heaters don’t require any type of electricity to operate. They run on propane or natural gas and are more expensive than electric heaters.
Wood-burning stoves: They’re affordable, but they require more work to maintain.
Hot water pipes: They’re typically used in larger commercial greenhouses. This system features a network of pipes that circulate hot water to heat the air inside the greenhouse.

No matter what type of heater you choose, it’s crucial to have a thermostat in place to help you regulate the temperature. Ideally, the temperature inside the greenhouse should be between 70-80°Fahrenheit (21.11-26.67°Celsius) during the day and 50-60°Fahrenheit (10-15.57°Celsius) at night.

Watering

Water is essential for plant growth, so you must ensure that your plants get enough of it. The amount of water your plants need will depend on the type of plants you’re growing, the size of the plants, the stage of growth, and the weather conditions.

Generally, you should water your plants when the soil is dry to the touch. Stick your finger 2-3 inches (5-7 cm) into the soil to check the moisture level. If the soil is dry, it’s time to water your plants. Overwatering provides the ideal conditions for root rot and fungal diseases, so it’s important not to water your plants too often.

There are several ways you can water your plants, including:

Hand watering: This is the most common method, and it’s pretty straightforward. Simply use a watering can or a hose to water your plants. Water at the base of the roots, being careful not to splash water on the leaves.
Drip irrigation: This is a more efficient way of watering plants because it minimizes evaporation and runoff. A drip irrigation system features a network of hoses and emitters that deliver water directly to the roots of the plants.
Sprinklers: Sprinklers are a good option if you have a large greenhouse. There are different sprinklers, including impact, rotary, and oscillating sprinklers.

Fertilizing

Fertilizing provides plants with the essential nutrients they need to grow healthy, strong, and fruitful. The fertilizer you use will depend on the plants you’re growing and their growth stage.

There are two main types of fertilizers:

Organic fertilizers: They’re made from natural materials, such as manure, compost, and bone meal. They’re less likely to burn the plants and release nutrients slowly, which is ideal for most plants. Over time, they improve soil structure and increase its water-holding capacity.
Inorganic fertilizers: They’re made from synthetic materials, such as nitrogen, phosphorus, and potassium. They’re more concentrated than organic fertilizers, so you need to be careful not to overuse them. Follow the manufacturer’s instructions on how to apply them.

Pest Control

Pests can wreak havoc on your plants, so it’s essential to keep an eye out for them. The most common greenhouse pests include aphids, whiteflies, thrips, and mealybugs. These pests are attracted to the warm, humid conditions inside the greenhouse, so they can quickly multiply and become a problem.

There are several ways you can control pests, including:

Handpicking: This is the most effective way to get rid of pests. Simply check your plants regularly and remove the pests by hand, and put them in a bucket of soapy water.
Encouraging predators: Predators, such as ladybugs and green lacewings, feed on pests. You can buy them online or at a gardening store and release them into the greenhouse. Planting certain herbs and flowers, such as marigolds and basil, can also help attract predators.
Using traps: You can use yellow sticky traps to trap and kill flying pests, such as whiteflies and aphids.
Using insecticidal soap: This is a safe and effective way to kill pests. You can make your own insecticidal soap by mixing 1 part liquid dish soap with 4 parts water.

The Best Crops To Grow in a Greenhouse

Greenhouses provide the ideal conditions for growing a wide variety of plants. Here are some of the best crops to grow in a greenhouse:

Vegetables: Tomatoes, cucumbers, peppers, eggplants, lettuce, spinach, kale
Fruits: Strawberries, raspberries, blueberries
Herbs: Basil, oregano, thyme, rosemary, cilantro, dill, mint
Flowers: Orchids, roses, carnations, daisies, petunias

This list isn’t exhaustive, but it should give you an idea of the types of plants that do well in a greenhouse. When choosing plants for your greenhouse, consider the amount of space you have, the growing habits of the plants, and your climate.

Tips for Successfully Growing Crops in a Greenhouse

A greenhouse allows you to enjoy fresh, homegrown produce all year round. However, you must follow the best greenhouse crop growth practices to ensure success. Here are some tips to help you get started:

Start with healthy plants: When buying plants for your greenhouse, choose healthy ones free of pests and diseases. Seedlings with lush green leaves are a good option.
Quarantine new plants: Pests and diseases find their way into greenhouses on new plants. Quarantine new plants for 1-2 weeks before adding them to the main greenhouse. This will give you time to check them for pests and diseases and treat them if necessary.
Keep the greenhouse clean: Pests and diseases love dirty conditions, so it’s essential to keep the greenhouse clean. Sweep the floor regularly and wipe down surfaces with a diluted bleach solution. Remove dead leaves and debris from the plants.
Provide adequate ventilation: Ventilation is crucial for excellent airflow and preventing fungal diseases. Open the doors and windows of the greenhouse on warm days to let in fresh air. Install fans to circulate the air if necessary.
Water the plants properly: Too much or too little water can harm plants. Water the plants early in the day so the leaves have time to dry before nightfall. Check the soil before watering to make sure it’s not too wet.
Control the temperature and humidity: The temperature and humidity inside the greenhouse should be just right for the plants you’re growing. Most plants do best in a temperature range of 60-70 °Fahrenheit (15.57-21.11 °C) and relative humidity of between 50-75%. Use a thermostat and hygrometer to monitor the temperature and humidity.
Feed the plants: Your plants will benefit from regular fertilizer feedings. Use a high-quality fertilizer and follow the manufacturer’s directions. Perform a soil test first to determine which nutrients the plants need.
Pest and disease control: Take measures to prevent pests and diseases from taking over your greenhouse. Inspect the plants regularly for signs like holes in the leaves, stunted growth, and wilting. Isolate sick plants to prevent the spread of disease. Use traps, insecticidal soap, or other organic pest control methods. Pesticides have lethal effects on beneficial insects and the environment, so use them only as a last resort.

Troubleshooting Common Problems When Growing Crops in a Greenhouse

You might encounter some problems when growing crops in a greenhouse, but don’t worry – you can fix them through a simple troubleshooting process. Common issues include:

Stunted growth: This can be caused by inadequate watering, poor drainage, low temperatures, or a lack of nutrients. Water your plants more frequently, improve drainage, and raise the temperature if necessary. Feed the plants with a balanced fertilizer to provide them with the necessary nutrients. Amend with a high-quality compost to improve the soil. Click on the link to learn more about fixing stunted growth in vegetable plants: How to Fix Stunted Growth in Vegetable Plants
Leggy seedlings: This problem is caused by insufficient light. Move the plants closer to the light source or install additional grow lights.
Yellow leaves: This could be caused by over- or under-watering, nutrient deficiencies, pests, or diseases. Inspect the plants carefully to determine the cause and take corrective action.
Fungal diseases: These diseases are caused by too much moisture and poor air circulation. Improve ventilation and water the plants early in the day, so the leaves have time to dry before nightfall.
Pests: Common greenhouse pests include aphids, whiteflies, and spider mites. Introduce beneficial insects to the greenhouse to help control pests. Use traps, insecticidal soap, or other organic pest control methods.

Conclusion

Growing crops in a greenhouse is an excellent way to enjoy fresh produce all year round. By following the tips in this guide, you can set up a greenhouse and grow healthy plants in no time. Remember to ventilate the greenhouse, keep the plants healthy and vigorous by following best practices for watering and fertilizing, and troubleshoot common problems to enjoy a bountiful harvest.