What to Grow in a Greenhouse

There are many possibilities with starting greenhouse gardening. But you may be wondering what vegetables you should grow in a greenhouse.

You can even extend the summer growing season by using an unheated greenhouse, cold frame, or even row covers over a raised bed to use during the cooler temperatures of fall and early winter.

After my husband built my dream greenhouse, I was excited to put it to use!

Two of my favorite things about gardening in a greenhouse is the extended growing season and starting my seeds in early spring. One of the best parts of growing a vegetable garden is planning and watching the tiny little seeds grow in to delicious vegetables.

In this post, I’m sharing a few of the best greenhouse growing varieties and where I purchase most of my garden seeds and supplies. 

What to Grow in a Greenhouse

If you are a beginner gardener, it is really important to know what growing season you live in. This will help greatly with planning out your garden. It also helps with seed starts and knowing what to plant in your greenhouse based on the seasons. 

You can even grow year round in a greenhouse in most climates with a few added tools. 

Ensuring that you have proper lighting and use of heat mats to start seeds are some key tools to keep handy.

An outdoor safe and greenhouse appropriate heater is also very helpful in making greenhouse gardening successful in winter months for most climates and garden zones. You can leave the greenhouse unheated if the the winters are milder.

But for us in the midwest, when the sub zero temperatures kick in, sometimes a heated greenhouse is necessary. Especially if you’re trying to grow plants year round. Or if you’re starting seeds that need a specific temperature for germination.

For the warmer months, having proper ventilation, air circulation, and sometimes using greenhouse fans are needed for growing success. Because the greenhouse can become extremely hot and you’ll likely burn your plants without proper ventilation.  

Growing Based on the Seasons

Knowing what types of food grows best based on the seasons will be helpful in planning out year round gardening in a greenhouse.

Some of these things will also vary depending on if you want to grow directly in the ground in your greenhouse or if you plan on growing using a container gardening method. I like to use grow bags for container gardening! They are such a good choice to consider for low maintainability.

Choosing the best greenhouse vegetables will depend on your growing season, type of greenhouse you are using, and selecting the best plants for the temperatures.

New to gardening? I have a really great resource for you! Check out my gardening for beginners ebook!

What Grows Well in a Greenhouse During the Warmer Months:

Tomatoes. Determine your space and the variety of tomato that you want to plant in your greenhouse. Some tomato plant varieties take up a large amount of space. Pruning and staking will help ensure that you have adequate space inside of your unheated greenhouse or high tunnel.

Peppers. These are usually slow growing and need warm temperatures for proper growth, and a greenhouse can be helpful to speed up growing. Pretty much any heat-loving plants like bell peppers, jalapeños, cayenne peppers, and ancho chilies are great options to consider.

Zucchini & Summer Squashes. These are another type of plant that you’ll want to ensure you have the adequate space planned out. They are a pretty fast growing crop which means you could see a pretty good bounty through the season. 

Beans. There are a ton of variety of beans that will do well in a greenhouse over the warmer months. Be sure to check out the recommended growing conditions for your specific variety.

Cucumbers. As with outdoor growing varieties, greenhouse cucumbers will provide more yields if they are grown vertically. 

Melons. Some varieties of melons, such as watermelons, grow well in a greenhouse. These plants usually grow pretty big, so ensure you have the adequate space before planting. 

Eggplants. The soil needs to be consistently warm for eggplants to be successful. They also can not germinate in cooler temps, so starting and growing in a greenhouse is a great option for getting an early start. Or if your spring temperatures fluctuate.

What Grows Well in a Greenhouse During the Cooler Months:

Herbs. So many varieties do well in a greenhouse almost all year round with the right conditions.. 

A couple of our favorite herbs to grow in a greenhouse are basil, cilantro, chives, dill, mint, and parsley. Mint is very invasive so it does well in a container where its not going to take over the garden.

I like to grow the more tender crops in terra cotta pots and move them to the greenhouse when the cold weather hits.

Green Onions. These typically do well in a cooler or a climate controlled environment making them a good candidate for greenhouse growing. They typically grow best in a temperature of 55-75 degrees. 

Garlic. Growing your own garlic is not too complicated if you ensure they have enough regular sunlight. They also prefer soil between 40-50 degrees so making sure that they have a heat source during the winter is important. 

Brassicas. Some of the more commonly known brassicas are broccoli, cauliflower, brussels sprouts, cabbage, kale, collards, kohlrabi, and radishes. Theses are all ideal for greenhouse growing.

Microgreens. Growing microgreens is incredibly simple and they grow relatively fast. Growing mats and adequate lighting will help with growing success. 

Lettuce. Temperature control is crucial for growing lettuces. Too hot or too cold and it just won’t thrive. Lettuces need a cooler environment of about 45-65 degrees. 

Spinach. Just like salad mixes, spinach needs a cooler environment to thrive. They also tolerate the cold fairly well once they’re well established. Spinach will need adequate protection from the cold while they are still young. 

Most leafy greens, Swiss chard, Brussels sprouts, green beans, French beans are great ideas to consider growing during the winter months.

Some more tips for growing in a greenhouse

Lighting is key to successful gardening. If growing in a greenhouse during winter or in places where the weather is often gray and gloomy, invest in a good grow light. 

A greenhouse safe heater for winter months and a fan for the hotter summer months will be helpful for temperature control. Keep better control with this temperature gauge.

Proper humidity control is also key. Since so many varieties of plants have different requirements, reading your seed packet and planning like items together will be helpful. 

If growing in the winter months, make sure you winterize properly before the cold weather hits. 

A good heat mat will be great for seed starting your plants in a greenhouse. 

Where I Purchase Seeds

In late winter, the garden dream starts with browsing through your favorite seed catalog. This is one of my favorite things about gardening – the dreaming!

Over the years, I have experimented with a variety of seed companies. I’ve had better success with some companies than with others. In the most recent years, I have become a loyal seed and transplant purchaser from a few awesome companies. 

There are a ton of great resources for purchasing seeds. But these are just my top choices and go-to companies.

True Leaf Market. This is where I purchase all of my microgreens. They have some really delicious varieties and the best options for growing microgreens at home. I also purchase my seeds for sprouting beans and legumes at home.

Siskiyou Seeds. This company has been a regular favorite for growing some neat varieties of plants. I really love their sunflowers, beans, corn varieties, and other florals.

Seed Savers Exchange. A really great option for heirloom and organic seeds! They have a few very specific plants that I love to grow each season.

Baker Creek Seeds.  If you are looking for some really cool varieties of plants, this is the place for you. They are well known for their rare seed varieties of plants. And I’ve always had great germination results here.