What to Grow in a Greenhouse in Winter

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The temperatures have dropped and the sunshine has lessened; it’s wintertime. Your greenhouse, though, is still equipped to grow and foster plant life, no matter the conditions. As we know, some plants simply cannot grow and thrive under these circumstances, but then again, some can. So, which plants are hardy enough to grow in the colder weather?

Luckily, there are several options of plants that can successfully grow in a greenhouse during winter.  Your winter greenhouse plant choices include:

  • Brussel sprouts
  • Spinach
  • Kale
  • Broccoli
  • Cabbage
  • Potatoes
  • Winter lettuce
  • Pak choi
  • Carrots
  • Garlic
  • Parsley
  • Leaf celery
  • Dill
  • Coriander

It’s important to keep in mind that because it is winter, the growth of these plants will not compare to Spring, Summer, and even Fall growth. Overall, daily progress will be much less than during on season and some plants will not reach full maturity for some time. None of this, though, means that plants can’t be grown during winter, as they absolutely can. With some patience until Spring, the payoff will be worth it.

The key to planting growth success during wintertime is ensuring the conditions are ideal. These conditions range from the proper amount of light and heat to the correct seed variations. And of course, lots of planning will go into this process.

To assist you in this planning process and make it the least complex as possible, it’s important to understand what exactly goes into proper winter greenhouse care. Luckily, you’ll be able to learn everything you need in no time.

Conditions for growing in the winter

All of these plants, vegetables, and herbs will show the most growth in the most ideal conditions.

Here are some of the most important tips to follow:

Keep Heat Locked in as Much as Possible

If your greenhouse isn’t heated, you can generate some heat sources of your own with things like electric heaters, heat pads place under pots or containers to warm the plant’s roots, and insulation.

You can also be sure to take advantage of the sun by creative passive solar bottles. The process for this is quite easy. All you’ll need are some clear water bottles, black paint, and water. Paint the bottle black and fill them with water. You can then scatter them around the plants in the greenhouse. The black paint will absorb any heat given off by the sun during the day and at night, that stored heat will automatically keep release to keep the plants warm.

Plant New Seeds in Pots

By planting the seeds in the pots you intend for them to stay in, there won’t be any added stress of transplanting them. Transplanting any kind of plant causes stress and can sometimes stunt growth if not done properly. This is something we hope to avoid altogether during winter as the conditions make things more difficult for these plants. By planting and prepping them in large enough pots early on, you are able to eliminate this risk completely.

planting seeds in pots

Choose The Best Seed Varieties

Each plant has dozens of seed varieties and some are better than others for colder temperatures. When searching for the best seed variety, be sure to take note of which ones are better in colder weather, making them cold-tolerant. It’s also helpful to look for seed varieties that have shorter growing seasons.

If you want to know what vegetables to grow in a greenhouse in winter then check this vegetable multi-pack (Amazon link). It’s a collection of 16,000 seeds of 35 different vegetable varieties. I think it one of the best vegetable multi-packs around

Plan Properly

If you are limited to one greenhouse, it’s important to make sure that the plants you’re putting together require similar needs and can handle similar conditions. Mixing plants with different needs will only add stress and not end well for some. Setting yourself up from the beginning is key.

What to Grow in a Greenhouse in Winter

The key to success in growing plants during wintertime in a greenhouse setting is choosing the best options. Some plants simply cannot handle the stress that comes with surviving the harsher climate and lower amounts of sunshine. Luckily, there are many that can so there are several options to choose from.

Potatoes

One of the best choices for winter planting is potatoes because of how simple their care is and how little they require. You can plant them in sacks or in larger pots and buckets. For the best growth, it’s recommended to fill whatever container you’re planting them in with two parts garden soil and one part compost. This combination creates an ideal environment for potatoes to survive and grow through the winter.

You can begin this process in early winter, November or December, and with the right care, you’ll be ready to enjoy potatoes by March or April. The most important thing to look out for when growing potatoes is a drop in temperature. They’re susceptible to frost so it’s imperative to keep them warm is the outdoor temperature has a sudden or large drop.

Brussel Sprouts

We may not have wanted to eat our Brussel sprouts as a kid, but they make an excellent winter vegetable in grow in your greenhouse. In total, they take roughly 3-4 months to mature and are typically ready to harvest by March.

It’s best to harvest them when they reach 1-2 inches in diameter, especially if you’re going to use them for cooking. Be sure to harvest similar sized sprouts so they have equal cooking times when it’s time to eat them, that is, if you’re finally ready to eat your Brussel sprouts.

Carrots

Another great and simpler option for your greenhouse is carrots. They can be planted in the fall and will be ready to harvest by the time the ground thaws, or once Spring arrives in your area. There are several varieties of carrots that can be grown, each with their own specific needs, so it’s important to do some research on the kinds of carrots you’ll be planting to find out if they’re compatible with the environment you can provide.

Spinach

Under the right conditions, spinach can easily become the gift that keeps on giving, all winter long. Not only does the vegetable grow rather quickly, but they also love cool weather. Take note that if the temperatures drop too low, you may find that the plant becomes dormant for some time. Worry not! This is normal and it will bounce right back once the temperatures rise again.

Because of its hardiness and comfortability in cooler temperatures, spinach is an ideal wintertime greenhouse plant that will surely produce plenty for you!

Lettuce & Similar Varieties

The wonderful thing about some varieties of lettuce and greens is that some of them are resistant to frost. Be sure to check for these when choosing the best seed.

It’s best to plant these seeds in the early fall and let them be throughout the winter months. Transplanting this vegetable will shock it and may stunt the growth entirely. The good news is, if left alone, they will not only survive winter but thrive in the greenhouse.

The ideal harvesting time for lettuce and similar greens is before they reach full maturity. You can also feel confident in mixing different varieties so come time to harvest, you have plenty of options to choose from.

Kale

This leafy, hardy vegetable can handle temperatures below freezing, certain varieties even more. If the temperature drops any lower for this plant, you’ll need to provide some kind of heat to ensure it doesn’t go into shock or fall completely dormant.

By planting and cropping Kale in successive cycles, you can easily harvest it year round. Fun fact: Did you know that Kale that’s grown during the winter months actually produces tastes sweeter because it produces higher levels of sugar to protect its cells from the harsher conditions?

Garlic

Are you a fan of garlic? If so, you’re in luck! Garlic navigates the winter months well and if planted in January can be ready to harvest by early March, depending on how early the soil is ready to be worked and if it needs to thaw.

If you plant garlic in a pot, you can also move it out of the greenhouse during warmer months and it will easily adapt to its new setting. If you choose to plant garlic in your greenhouse during winter months though, make sure you choose a hardback variety rather than a softneck variety. Hardneck varieties of garlic are hardier and can adapt much easier to the cold.

Pak Choi

This vegetable that originates in northeast Asia takes only 30 days to leaf and roughly 70 days to harvest. Because of the environment it originates from, it can navigate colder and harsher elements better than most.

Pak choi is an excellent plant to consider, not only because of its ability to flourish during the winter, bit also because of its nutrient rich leaves. This plant is packed with vitamins and is sure to be a healthy addition to any meal.

Cabbage

If you’re able to keep your greenhouse at an optimal temperature and keep the environment conducive for more picky plants, cabbage does have the ability to do well. While it requires more attention and care, the pay off is worth all the work.

This plant is much more sensitive to temperature and will definitely require steady supervision but can handle the winter months if cared for properly.

Broccoli

Much like cabbage, this vegetable is more sensitive to temperature than most of the others on this list. Nevertheless, it is still a great option for winter planting in a greenhouse under the correct conditions.

If you do choose to plant broccoli, it’s best to start early in November if you’re looking for a Spring harvest. Broccoli is another plant than can be moved outdoors in warmer temperatures and handle the change very well.

Winter Greenhouse Gardening Tips

Gardening and reaping the benefits of harvesting your own plants are activities you shouldn’t have to miss out on simply because the winter months have rolled around. Luckily, there are several plants, herbs, and vegetables that can navigate through these months with the right level of care. Additionally, there are some helpful tips that can make this process somewhat more manageable.

Cleaning and Preparing Your Greenhouse

For optimal results and the best possible environment for your plants, your greenhouse will need to be fully prepped and cleaned before the planting process begins. Although it may not be your favorite part of gardening, it’s just as necessary as any other step.

By cleaning the walls and roof, you’re removing potentially built up mold, dirt, and algae. The removal of these unwanted toxins clears the air for your plants and also allows for more light and heat to come into your greenhouse. Your plants will thank you for this and express their gratitude through the production of more leaves!

The best way to clean is by first picking a mildly temperate day. You can begin by removing everything from the greenhouse to get the best clean possible. Make sure to keep your existing plants somewhere safe and secure during this part.

Disinfect all of the structural components of your greenhouse with a solution of your choice. It is recommended to use garden-specific solutions that won’t leave behind toxins for your plants to become exposed to. And above all else, hot solutions work the absolute best.

You can also double back and use a glass cleaner on all of the greenhouse panels to scrub and get a more thorough clean. Again, garden-specific or green/eco-friendly products are always best for this kind of job.

Lastly, be sure to vacuum, sweep, or both to ensure all of the fallen and remaining debris is completely removed from your greenhouse. You can then return your plants into the space and organize them in a fully ready and prepped greenhouse for them to live in all winter long.

Ventilation for a Winter Greenhouse

An often overlooked step in preparing a greenhouse for a long winter is ventilation. A common question asked is do greenhouses need ventilation? If you are able to ventilate your green hosue then please do.

Just like people, plants need access to clean air too. Without a properly ventilated space, plants can become trapped with too much oxygen, too little carbon dioxide, and even toxins that can sneakily find their way in.

Did you know that if plants don’t have access to enough carbon dioxide, they can become leggy? Furthermore, if they don’t have access to enough oxygen, they’re unable to process transpiration. Moral of the story, plants must have proper ventilation in the greenhouse to survive.

Luckily, achieving this is quite easy. Leave your greenhouse doors open at the start of the day and close them when the sun goes down. This also avoids too much humidity building up in their environment, causing mildew and even disease.

Insulation for a Winter Greenhouse

It’s an absolute must for your greenhouse to retain enough heat for your plants to survive. Providing supplementary heat, as mentioned above, is key in achieving this. It also helps the heat produced by the sun to remain in the greenhouse without escaping too quickly.

Check out my article – Do greenhouses need a heater – which answers a lot about this – In short I would recommend investing in a heater especially if you play to grow during the winter months.

The step of adding a heater may be somewhat timely and require adjusting to learning what works and what doesn’t. With that being said, it’s important not to skip this step entirely. Doing so would make all of your hard work, well, not pay off.

Harvest Efficiently

One of the biggest mistakes that gardeners make when harvesting plants in the winter is that they treat it the exact same way as they would a Spring or Summer harvest. Unlike these warmer weather harvests, winter harvests should be spread out and not done all at once.

It’s recommended to take into account the scheduling of each plant and be deliberate in when the ideal harvesting time is for each one specifically. By harvesting at the correct time, you’re enabling the plant to continue to grow at a steady rate and not stunt or shock the plant.

It’s important to remember, too, that your winter harvests will be much smaller than your warmer weather harvests, in addition to being spread out. As we know, plants do not thrive the same way or at the same rate as they do in the Spring in Summer. So, be realistic with your expectations of each.

When it comes time for you to decide to what to grow in a greenhouse in winter, the options are far more expansive than you may realize! The best thing to do? Just try it out and give it your best shot. Be open to learning as you go, making adjustments, and knowing that not every plant is going to respond perfectly as you learn. And that’s okay.

Ultimately, gardening can be fun and beneficial, even during winter. By following these tips and trying the plants listed above, you’re sure to reap some delicious benefits come springtime!

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