Not everyone lives in a temperate climate, so it’s good that there are many crops suitable for greenhouse farming. Although even if you do, having a greenhouse still presents a major advantage when growing your own food. Greenhouses make it possible to start plants earlier in the season, grow crops that are too delicate for the outdoors, and still harvest well into the colder weather. If you already have a greenhouse, you may be familiar with some of the best crops suitable for greenhouse farming. But if you’re considering buying or building a greenhouse of your own, no doubt you will want some pointers on what exactly to grow in there. Whether you have a greenhouse already or you’re planning one, remember to think out of the box – there are some unusual greenhouse crops (detailed later in this article!) that you may want to consider, too!
- What Are Greenhouses For?
- How Does a Greenhouse Work?
- Considerations For a Greenhouse
- Different Types of Greenhouses
- 20 Crops Suitable For Greenhouse Farming
- What to Grow in a Greenhouse in Summer
- Unusual Greenhouse Crops
- What Crops Are Suitable for Greenhouse Farming Where You Live?
What Are Greenhouses For?
Dedicated gardeners, commercial plant growers, homesteaders, farmers, and botanists mainly use greenhouses to achieve year-round propagation and growing of plants – especially in cooler climates. Greenhouses stay warm enough to grow almost any crop or plant, and if they are constructed properly and heated appropriately when there is less sun, they can be used successfully throughout all four seasons. Greenhouses also protect delicate plants from the elements (wind that may damage them, for example) and other plants that wildlife might look to a quick snack!
How Does a Greenhouse Work?
The main purpose of a greenhouse is to maximize the comfort of the plants you are growing. You aim to have the exact amount of light, moisture, and temperature that will encourage plants to grow at their very best. Some greenhouses are dedicated strictly to food crops, while others are focused on houseplants and flowers.
A greenhouse has a ceiling made from glass or another material that will let in light and trap heat inside. Once it gets dark outside, the temperature inside a greenhouse does not drop at the rate it would outdoors. This is why plants and flowers that do not tolerate temperature drops well seem to flourish inside a greenhouse.
In more scientific terms, short wavelength infrared light enters the greenhouse, either from the ceiling or the walls, depending on the height of the sun. As these warm but invisible rays bounce around, they become electromagnetic energy. They remain inside the structure and are absorbed by their surroundings. Within a greenhouse, these surfaces include the leaves on plants. The leaves then use the sunlight to begin photosynthesis.
What Are Greenhouse Gases?
Most of us are familiar with the term ‘greenhouse gases’. While they may not be so desirable in the atmosphere, their chemical structure is perfect for growing plants. Nitrous oxide, methane, carbon dioxide, and water vapors are the main greenhouse gases. While most molecules are tightly connected, the molecules in these gases are looser, enabling them to vibrate when struck by heat. While vibrating, heat is released and then mostly absorbed by other greenhouse gases in the vicinity. This continuing cycle keeps the air within the greenhouse warmer than normal.
Considerations For a Greenhouse
There are several things to consider when constructing a greenhouse. The most important are size, ventilation, and materials.
- Size: The size of your greenhouse will ultimately depend on the space you have available for it, so go as big as you can. For the average home gardener, you should look at having a width of at least 8 feet, and a height of at least 6 feet. The length is variable. If you have at least 8 feet in width, you are able to put shelves on both sides of the greenhouse. This will increase your harvest drastically.
- Ventilation: Your greenhouse needs to be properly ventilated, especially during the heat of summer. Most gardeners agree that the optimum ventilation setup would have one vent on the side and two in the roof, but this could vary depending on your climate.
- Materials: Greenhouses can be constructed from a variety of materials and each has pros and cons. Polycarbonate is relatively strong and insulates well, but it does not let in as much light as other options. Aluminum is low maintenance and cheaper than wood, but it does not insulate so heat can be lost through the frame. Wooden greenhouses are attractive and great at keeping stable temperatures, but may need regular treatment, which can be costly. Glass is used frequently, especially for smaller home greenhouses, but can break and is costly to replace. Then there are greenhouses that have clear plastic tarping stretched over metal hoops; these are inexpensive and easy to set up, but can tear easily.
Different Types of Greenhouses
Greenhouses are grouped into two types: growing needs and temperature. Starter greenhouses, cold frames, and grower greenhouses are types of growing needs.
- Starter greenhouses: These are usually small and you can use them to start seeds or grow seedlings before moving them outdoors.
- Cold frames: These are moveable mini-greenhouses that you can use to harden off plants. Usually, you put cold frames over plants to protect them from cold temperatures. Some growers also use them to grow plants that prefer colder temperatures, even in the summer, as you can use them for cooling too.
- Grower greenhouses: These are larger-sized greenhouses that have either semi-diffused or diffused coverings. Generally, you use them as a shelter for houseplants. If it is big enough, it can be used for multiple purposes, like growing crops, propagating seeds, preparing plants to be stored, or curing harvested plants.
Types defined by temperature include: cool greenhouses, warm greenhouses, and hot greenhouses.
- Cool greenhouses: These have a temperature of approximately 39-46 degrees Fahrenheit (4-8 degrees Celcius). Often used as a nursery greenhouse, the conditions are excellent to raise starter plants or grow seeds before putting them outside in the summer.
- Warm greenhouses: These greenhouses grow plants that are generally found in summer vegetable or flower gardens. In cold climates either grow lights or heaters are needed to maintain the desired temperature of between 50-55 degrees Fahrenheit (10-13 degrees Celcius). However, what to grow in a greenhouse in summer will depend on where you live (see below for some recommendations).
- Hot greenhouses: These are particularly useful for growing tropical fruits, vegetables, or flowers because you can increase the temperature considerably. Both high-quality grow lights and heaters are used to keep the temperature stable at a high level, usually between 66-71 degrees Fahrenheit (19-22 degrees Celcius).
20 Crops Suitable For Greenhouse Farming
People love to purchase vegetables that are grown locally, either in greenhouses or gardens. As most of us know, they just taste so much better than what is available in the stores! Most of what we have available in stores has spent many days in transit before it even reaches the shelves. No wonder it is so often lacking in bright colors and freshness!
There are many crops that are suitable for greenhouse farming but here we concentrate on the best of the best. You want to choose crops that will grow quickly, and where possible, ones that you can get more than one harvest from. One thing to remember is that greenhouses make fabulous use of space when you plant crops that can grow vertically!
- Cucumbers: Cucumbers are a great crop to plant and sell from your greenhouse. There are many varieties available and they go very well vertically. They also produce for long periods.
- String beans: These have to be one of the easiest crops to grow. Period. They grow vertically and take up virtually no space. You can have a continual harvest by planting every week or two. It is also astonishing to see how many beans you will pick from each plant.
- Chili peppers: Most chili peppers in the store look unappealing and have no firmness. When you are able to pick them in the morning to sell later in the day, customers will flock to get fresh peppers, especially when you have different heat levels.
- Tomatoes: These are easy to grow and there are hundreds of tomato varieties. Plants are prolific growers that reward you with pounds of fruit per plant. You should have no issue with broken stems and a decreased harvest if staked properly.
- Spinach: Spinach is a wonderful money-making crop. It grows quickly and when cut down, it just grows back. You are able to sell spinach from the same plant what feels like an unlimited amount of times in a season.
- Microgreens: These are one of the newest superfood crazes. Microgreens practically grow themselves – they are so simple! These tiny, tender versions of greens like basil, beet, cress, mustard, and others are nutrient-rich as well as delicious. They sell for a high price and need only 2-4 weeks before they can be harvested. Many growers find local restaurants that quickly purchase their supply.
- Peppers: Peppers sell well for any grower, especially when you offer more than the standard green pepper. The attractive colors of orange, red, and yellow peppers draw plenty of interest at farmer’s markets.
- Melons: It is difficult to get melons in the store that last more than a day or two when you bring them home. They are easy to grow and the numerous varieties give plenty of options to buyers. The fresher the fruit is, the more a customer wants it.
- Peas: You can plant peas very early and succession planting means that you will be able to sell them all season long. There are various kinds and most have excellent harvests. Since they will grow vertically, you can plant a ton of peas in quite a small space.
- Leeks: Fresh leeks are always a winner for growers. They fetch a good price and require relatively little ongoing care and attention.
- Sweet corn: Corn is the quintessential summer crop. Farmers race to get their corn out for sale. It grows phenomenally well in greenhouses and one benefit is that you will not have to worry about damage from deer, raccoons, or squirrels. Severe weather can be an enemy to corn, though, so keep it safe inside a greenhouse and there will be no need to worry about strong winds taking it down.
- Baby carrots: The baby carrots sold in most stores hardly taste like carrots at all sometimes. All the more reason to grow your own! Since they are short, baby carrots work well even in greenhouses without a lot of soil depth. They do not take long to mature and they sell well.
- Broccoli: Broccoli can be hard to get the hang of, but once you do there is nothing like the taste of it fresh. Far from the brownish clumps often seen at the store, these will be bright green and tasty when put up for sale (if you don’t eat them all yourself!)
- Pumpkins: Pumpkins are a great greenhouse crop, but you have to train them to grow in the direction you want. Otherwise, you will walk in to find that they have taken over every crop nearby. Unless you are growing pie pumpkins, the only real market is late fall, but almost every grower sells out around this time of the year.
- Garlic: Fresh garlic, not the hard stuff at the local grocery store, is a dream for those who love to cook. Since you plant it and leave it until harvest, it is basically maintenance-free. Garlic always sells well at any time of the year, too.
- Herbs: The possibilities are endless when it comes to the choices you have for growing herbs. You can go with classics like mint, thyme, rosemary, and basil, or branch out a bit into medicinal herbs like echinacea, calendula, chamomile, ginger, or feverfew. The rarer the herb, the steeper the price you can sell it for (check out our article on profitable herb growing, if you haven’t already!)
- Squash: Many types of squash like spaghetti or acorn are easy to grow and can be harvested at various sizes. These always sell well for growers but do require more room than other crops, so bear that in mind in your greenhouse planning.
- Swiss chard: This colorful and leafy green is a must on the crops suitable for greenhouse farming list. If cut down it will grow again, meaning you can sell it over and over. It also does not take long to grow.
- Kale: There are many different types, and almost all salad blends now include kale. It is speedy to harvest, easy to care for, and easy to sell.
- Zucchini: Zucchini is popular for stir-frys and makes wonderful bread and muffins. The large zucchini found in greenhouses is far superior to the thin versions found in most stores. You can even grow it vertically! It is rare to go to a roadside stand or farmers market and find they have any left for sale.
What to Grow in a Greenhouse in Summer
In practice, you can grow anything in the greenhouse in the summer, including the plants on the list above. These are a few popular choices that do well with the extra protection four walls affords, however! Here’s what we recommend:
- Strawberries: One of the worst things about growing strawberries is that the birds and other animals that pick them before humans do. What may look to be a bumper crop judging by the flowers, may be picked bare two weeks later. Growing these in a greenhouse ensures that the humans get the first pick.
- Grapes: Grapes are great to grow in a greenhouse because they can be properly supported and trained to grow the way you want. They can be impossible to control when they grow wild against fences or buildings. If they do grow outside, you have to worry about birds and other animals eating them before you do.
- Lettuce: Lettuce is perfect to grow in the greenhouse in summer. Why? It grows quickly, and it grows back quickly when you cut it. Having it in the greenhouse protects it from deer, chickens, and wild rabbits.
- Raspberries: This sweet-tart fruit has many of the same problems as strawberries and grapes. Animals find them just as tasty as we do. At least you can protect them in the greenhouse in summer when the most rampant vegetable patch foragers arrive!
Unusual Greenhouse Crops
If you try hard enough, it is possible to grow practically anything in a greenhouse. There are some rather interesting crops that can be grown in the home greenhouse. Some of them can also provide you with a significant second income if that of interest.
- Mushrooms: Mushrooms are relatively easy to grow in a greenhouse as long as there is plenty of manure. They are care free and boast a good crop for most growers. Specialty varieties like shiitake and oyster do especially well. Fresh and dried mushrooms sell very well. Per square foot, you can expect to harvest around 25 pounds of mushrooms.
- Ginseng: Ginseng is a root that has been favored in traditional Chinese medicine for centuries. The price ginseng fetches has growers keeping a close watch on their crop. It grows wild in the central and eastern United States, and in southeastern Canada. As North American ginseng is so similar to Chinese ginseng, it is very popular.
- Bamboo: Most shrubs and trees take years to mature. Bamboo, however, matures quickly and has a large profit margin. It is not uncommon to see a bamboo plant grow two feet or more within 24 hours. It is in demand for landscaping and for commercial production of linens and other items. If you intend to sell potted plants, a large and healthy bamboo can fetch around $200.
- Citrus fruits: Lemons, limes, and oranges do very well in greenhouses with the right conditions. Growers can either harvest the fruit to sell, or they can sell starter plants for people to grow in their homes.
What Crops Are Suitable for Greenhouse Farming Where You Live?
Having a greenhouse is great fun for everyone, even if you only intend to use it for your own plants and flowers. What’s nice is that greenhouses come in so many shapes and sizes that you can make them fit in virtually any space. If you only have space for a small version, choose some of the above crops that are suitable for greenhouse farming so that you know you’re making the most of the space. Once you become used to greenhouse growing, you may want to experiment more and even expand your space! Whether starting big or small, any of the crops on the lists above are a great choice to get up and running. What are you going to plant?