There’s nothing quite so satisfying as eating fresh vegetables from the garden. But depending on your climate, what and when you can grow in an outdoor vegetable garden is limited. By investing in a greenhouse, you unlock countless new gardening opportunities, including the ability to grow a range of vegetables year-round!
Greenhouse vegetable gardening is not unlike growing outdoors, but that doesn’t mean you can go in expecting to be able to do everything your first year. To ensure the success of your greenhouse vegetables, it’s important to start simple, set realistic expectations, and come up with a plan.
Even a small greenhouse or an unheated greenhouse can make growing vegetables throughout the year much easier. In this article, we’ll go over some tips and tricks that will help you make the most of your greenhouse.
Benefits of a greenhouse vegetable garden
While it’s not necessary to have a greenhouse in order to grow your own vegetables, it is a valuable asset to gardeners of any level, from beginners to professionals!
Some of the benefits of having a greenhouse include:
- Extending the growing season by several weeks or months
- Starting vegetable plants off early to get a head start on the season
- Growing tender crops such as tomatoes, peppers, and eggplants in a protected environment
- Experimenting with growing exotic, rare, or tropical plants such as loofah, okra, or kumquat
- Growing citrus trees in a cold climate
- Making the most of the sun in late fall to grow plants such as broccoli, French beans, and lettuce
- Overwintering cold-tolerant crops such as carrots, beets, and kale for year-round harvesting
What is the best season for growing vegetables in a greenhouse?
If you’re new to greenhouse gardening, you may not only be wondering how to grow vegetables in a greenhouse but also when. The answer to this question is: it depends.
Different greenhouse designs are better suited for different climates. For instance, a well-insulated greenhouse, such as one made by Solexx or MONT, can be used as a winter greenhouse in mild climates or in cold climates with additional heating. In a hot climate, however, a well-insulated greenhouse would get too hot to grow most plants, so a greenhouse with plenty of ventilation would be a better fit.
No matter which type of greenhouse you have, the shoulder seasons (spring and fall) are generally considered the most important for greenhouse growing as they allow you to extend your growing season with ease. But as you’ll see, you can grow vegetables in a greenhouse in most seasons:
Late winter to early spring
For most greenhouse gardeners, late winter to early spring is crucial to getting an early start on the main growing season. Depending on your climate, level of greenhouse insulation, and any additional heat sources, this can be anywhere from January to April.
From late winter to early spring you can sow hardy plants (peas, onions, leeks, celeriac, cabbage and Brussels sprouts) in seedling containers, using a seedling heat mat to speed up germination. Transplant these vegetables outside once the weather warms up, or continue growing them in your greenhouse if space allows.
Additionally, early spring is the best time to grow cold-hardy, fast-growing vegetables such as arugula, lettuce, spinach, and carrots. If timed properly, you’ll be able to get several rounds of harvesting in before it’s time to replace them with warm-season crops.
Spring
In mid-spring, once temperatures have warmed up enough and your greenhouse nighttime temperature remains above 60°F, you can sow warm-season vegetables such as peppers, tomatoes, corn, French beans, cucumbers, pumpkins, and zucchini.
Even if it’s still too cold to grow heat-loving plants outdoors, starting them early in the greenhouse helps you get a head start on the season. This is crucial in areas with short summer growing seasons. If you are lucky enough to have a long growing season, you’ll still benefit from an extended harvest period, especially if you practice succession planting.
Throughout the spring, cold weather is still a possibility. Therefore, it’s best to use precaution and use seedling heat mats or even a space heater to protect your young plants. Make sure to supplement with artificial light if your greenhouse isn’t receiving at least 8 hours of sun.
Summer
Summer is the most exciting season for any gardener because plant growth speeds up considerably with the warmer temperatures. While you can continue to use the greenhouse throughout the summer with proper ventilation, many greenhouse gardeners find that the temperatures get too hot for growing much besides heat-loving plants such as tomatoes, peppers, and eggplants.
That said, late summer is the best time to start sowing cool-season plants such as brassicas in preparation for the fall.
Early fall
With early fall come cooler temperatures, when you can once again grow cold-loving vegetables such as kale, lettuce, and broccoli in your greenhouse. If your greenhouse will remain unheated during the winter but you live in a mild climate, we recommend sowing some root vegetables at this point. They will grow to maturity in the late fall or early winter, but you can leave them in the soil through the winter for convenient harvesting!
Finally, as growing slows down for the year, consider preparing your greenhouse for winter by doing a deep clean!
12 tips for growing vegetables in a greenhouse for beginners
Your understanding of how and when to grow vegetables in your greenhouse will help you grow the best vegetables. Here are some more tips that will be sure to help you out:
Start simple
We get it: you’ve been dreaming of your perfect greenhouse for a long time, and know exactly what you want to grow in it! However, when you first start growing vegetables in a greenhouse it’s best to keep it simple. This will allow you to be successful right away.
That means only selecting a handful of crops to grow your first year. It also means sticking with just one or two varieties of each crop instead of trying to grow them all.
Set realistic expectations
When growing in a greenhouse, especially early on, it’s important to keep your expectations realistic. You may not be able to grow tropical fruits in your greenhouse year one, or grow tomatoes in the dead of winter. Instead, consider viewing your greenhouse as a way to extend your growing season and focus on crops that are easy to grow.
Create a calendar
Just as with an outdoor garden, it’s important to create a personalized growing plan for your greenhouse vegetable garden. Remember, when you’re starting out it’s important to keep it simple, and that applies to your plan, too.
Practice crop rotation
Minimize the risk of pests, disease, and nutrient deficiency by practicing crop rotation in your greenhouse beds. If you’re growing in pots, switch up what kinds of plants you grow in which pots, or completely switch out the soil with fresh potting mix. You can recycle spent soil by adding it to your outdoor garden beds or the compost heap.
Maximize your space
No matter how big or small your greenhouse is, it’s important to maximize your growing spaces. Use shelves and trellises to utilize vertical space and hang baskets from the ceiling to grow smaller vining plants such as strawberries. Use the space underneath shelves, where it’s too dark to grow anything, for storing your tools and supplies.
Pay attention to your water
Water is a crucial element of any successful vegetable garden. However, tap water is not always ideal for growing healthy vegetables. For this reason, we recommend collecting and using rainwater. If this is not possible, you can install a water filter in your greenhouse to remove impurities and ensure your plants are receiving clean water.
Enrich your soil
Since your greenhouse garden is more or less a closed system, it’s important to make sure you’re using a well-balanced potting mix to prevent introducing any pests or disease. As you start growing in your greenhouse, continue providing your plants with plenty of nutrients by enriching the soil with aged compost, manure, or worm castings.
Provide opportunities for pollination
If you’re growing anything that requires pollination in your greenhouse, you’ll need to provide opportunities for pollination by opening windows and doors during the day to allow in beneficial insects. To increase the chances that pollinators find your greenhouse, grow flowers nearby or inside.
If you want to keep your greenhouse a closed system, you’ll need to hand-pollinate or grow only self-pollinating plants.
Monitor the temperature
A greenhouse provides crucial insulation during the colder months, but that doesn’t mean your plants can’t get damaged if temperatures drop too low. Prevent frost damage by monitoring temperature, and if a frost is imminent, protect your plants with frost cloths, heaters, extra insulation, or passive heat sources.
On the other hand, greenhouses are prone to heating up quickly during the summer. To prevent your greenhouse from overheating, use shade cloths, allow for plenty of ventilation, and install a fan.
Check regularly for pests and disease
While your greenhouse provides protection from the elements, that doesn’t mean that your plants are immune from pests and disease. In fact, pests and diseases may even hit harder in a greenhouse because it is a closed environment. Therefore, it’s extra important to be vigilant and check regularly for signs of pests or disease.
Prevent an outbreak by practicing good sanitation, including cleaning work surfaces and doing a deep clean at least once a year. Additionally, try to avoid moving plants in and out of the greenhouse to prevent potential contamination. Isolate plants that show any signs of disease. Yellow sticky traps are a great way to keep fungus gnats and other flying insects at bay.
Harden off plants before planting them outside
If you’re using your greenhouse as a season extender or to start seedlings, you may be growing vegetables that you plan to move outdoors. The greenhouse is a protected environment, so you don’t want to move plants outside without hardening them off first. Do so by placing plants outdoors for a few hours at a time each day, building up the time over the course of a week before finally placing them outside 24/7.
Fertilize
Even if you’ve amended your greenhouse garden soil with compost, you should consider fertilizing your plants to ensure they get enough nutrients. We recommend a schedule of roughly every 2-4 weeks using a diluted fertilizer (follow instructions on the product label).
FAQs about growing vegetables in a greenhouse
Do you need a greenhouse to grow vegetables?
You do not need a greenhouse to grow vegetables. Although a greenhouse is a valuable tool for extending the growing season, it’s not necessary except for in more extreme climates, where the natural growing season is not long enough for growing most vegetables.
Is it better to grow vegetables in a greenhouse or outside?
You can grow vegetables in a greenhouse or outdoors with great success. Vegetables grown in a greenhouse may benefit from the protected environment. Conversely, outdoor plants tend to be stronger and more resistant to adverse conditions, including drought and wind. Ultimately, it’s up to you where you want to grow your vegetables, though a greenhouse is typically more limited in space.
Are greenhouses good for growing vegetables?
Greenhouses are an excellent tool for successfully growing vegetables! While they are often used as season extenders, you can grow exclusively in a greenhouse if you have no other option. As long as the greenhouse has proper ventilation and sunlight exposure, vegetables will thrive just as they would outdoors.
Do vegetables grow better in a greenhouse?
If greenhouse conditions are properly controlled, it is very possible that vegetables grow better in a greenhouse than outside. Protected from the elements and pests, vegetables are able to focus their energy on growing. And if the greenhouse growing environment is supplemented with heat and light as needed, it’s possible to create even better conditions for optimal growing.
Can you grow vegetables in a greenhouse in the summer?
In mild climates, you can grow vegetables in a greenhouse in the summer. The reason that summer can be more difficult for greenhouse growers is because greenhouses (especially small ones) tend to heat up quickly. Fans can help keep temperatures down, but then the soil may dry out more quickly. Therefore, growing vegetables in a greenhouse in summer may require extra vigilance.
