By: Anne Baley
If you’re like most gardeners, you’re probably ready to get your hands on some dirt by the middle of winter. If you install a hobby greenhouse next to your home, you may be able to make that wish come true virtually every day of the year. Growing vegetables in a hobby greenhouse allows them to extend the season, sometimes by months, giving you a year-round gardening opportunity. While you can’t grow all vegetables in a greenhouse 12 months of the year, you can plant cool-weather vegetables and let them grow through the worst of the winter weather with a simple heating system installed.
How to Grow Vegetables in a Greenhouse
Greenhouse vegetable plants may end up growing faster and stronger than those grown in a traditional garden, because you will be giving them the ideal environment for growth. When it’s below freezing outside, passive solar collectors and small heaters can leave the interior of a greenhouse cool but perfectly liveable for most spring vegetables. In the heat of the summer, fans and other cooling units can protect tender plants from the scorching heat of a southern climate.
You can grow greenhouse vegetable plants directly in the soil inside the enclosure, but container gardening is a more efficient use of space. You can take advantage of all three dimensions by placing planters on shelves, using trellis systems for vine plants and hanging planters for smaller vines, such as cherry tomatoes and strawberries.
Winter Vegetable Growing
Growing winter veggies for greenhouses is possible because most cool-season plants can tolerate temperatures near freezing, as long as their soil isn’t muddy. Container gardening solves that problem by giving the plants a perfect mix of potting soil.
If you’re planning on winter vegetable growing when building your greenhouse, add a passive solar collector such as a wall of black-painted water jugs. This will collect solar heat during the day and reflect it into the greenhouse at night, helping to prevent freezing. Add an additional small heater, either propane or electric, for the coldest days of the year.
Once you have the greenhouse built, experiment with plant placement for the best growing conditions for each variety. Cool season plants such as peas, lettuce, broccoli, carrots and spinach all have slightly different needs, and moving them around in the enclosure is the best way to find what works best with each plant.
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Winter Gardening Projects for the Vegetable Garden
These twenty winter gardening projects and tasks will keep you busy in the colder months and prepare the garden for the year ahead
We’re deep into winter, but that doesn’t mean that we have to stay inside, twiddling our green thumbs. There’s plenty to do to prepare for the vegetable gardening year ahead. Building hardscaping, planning what to grow, and where, and getting organized. There are even seeds that benefit from being sown now, under the warmth of grow lights. Use this list of winter vegetable garden tasks to get a head-start on this year’s garden and prepare for the harvests ahead.
1. Build raised beds, paths, and other hardscaping
Winter is the perfect time to build projects for the garden. Create raised garden beds, garden paths, rose arbors, sheds, or plant supports like berry trellises. Trust me, it’s stressful to get these types of projects done when you’re trying to grow crops at the same time. Build them as a winter gardening project and you’ll be all set for spring growth.
Build garden features such as pathways, plant supports, trellises, and garden beds
2. Make newspaper plant pots
If one of your goals is to recycle more and useless plastic, make newspaper plant pots. The paper and ink are safe for growing plants, and the pots last just long enough before they begin breaking down. It works out well because by that time, you can plant, newspaper pot and all.
I share two ways how to make newspaper plant pots over here
3. Use pruned raspberry canes
Winter is when we prune raspberry canes. Mine are autumn fruiting varieties, so I cut them all down to about two inches from the ground. With summer fruiting, you only cut the old wood. Regardless, you’re left with a bundle of canes that are usually burned or composted. Instead of disposing of them, use them to make raspberry cane wattle edging. My first one lasted three years before I took it down. During that time, it helped keep the compost contained in the raspberry bed. Since the canes are hollow, they also provide homes for insect life.
Use pruned raspberry canes to make garden edging
4. Plant bare-root strawberries
Most people who plant strawberries will have purchased them in pots in spring. Those in the know are wise enough to think ahead and order them bare-root. Bare-root strawberries arrive in the winter and need planting then too. If it’s mild enough, you can plant them directly in the soil, but it’s sometimes better to plant them in pots and grow on in the greenhouse first. Bare-root strawberry plants are far cheaper than potted plants, and you’ll have a lot more choice in variety too.
Bare-root strawberries arrive like this in the winter. You plant them in pots or direct in the garden.
5. Plant an Edible Hedge
If you have enough land, you cannot go wrong with planting an edible hedge. They’re great boundary plantings, provide habitat for wildlife, and with very little work on your part, will produce crops of nuts, berries, and fruit. It’s a win-win situation. We have a ‘Gin Makers Hedge‘ planted at our allotment, kindly donated by Hopes Grow Nurseries. It arrived two years ago as bare-root shrubs and I dug them in late February. Two years on it’s beginning to fill in with various types of wild rose, sloes, elderberries, wild cherries, wild pear, and more. There are other nurseries out there that can supply bare-root edible hedge plants too, but you’ll need to order and plant them in winter.
Edible hedges produce crops of wild berries and fruit
6. Build a grow-light system
Having a dedicated grow-light system gives you far more space to start seeds in winter, and you can even use it to grow salad crops in the cold months. All you need to build one is a little space, shelves, and the right lights. You can even use it to start seeds indoors for planting out after the last frost. I recently invested in a metal shelving rack and two suspended grow lights. They weren’t cheap but I did start a lot of seedlings off early this spring.
If you’re on a budget all you have is a window sill, I’d recommend you get this clip-on grow light. I’ve used it for two years and love how it makes that space a better-growing place for seedlings. With it, you don’t have to worry about them becoming leggy as they reach for the light. The seedlings benefit from both natural daylight and supplemental light from above.
7. Deep Clean the Greenhouse
Before spring sowing and growing begins, deep clean the greenhouse. It gives you a chance to clean the glass, improving light, remove pests, and sanitize growing spaces. If you have problems with slugs, spider mites, or fungal infestations (plants, not your toes!) then that’s even more reason to tackle this as early as possible.
8. Begin forcing rhubarb
Forcing rhubarb creates very early, tender stems of bright pink rhubarb. It’s much more of a thing in Britain, but I hope those of you in the USA and abroad give it a go too. Though you can use a traditional terracotta rhubarb forcing pot, placing a clean rubbish bin (garbage can) over your plant does the same thing. It warms the air and ground around the rhubarb and encourages it to grow up to a month earlier.
Forcing rhubarb creates tender and sweet pink stems
9. Chit potatoes
Although you can plant potatoes that are not chitted, some people swear by giving them this head start. Chitting means setting your seed potatoes in a bright place for about four-to-six weeks before planting them out. Setting them in egg cartons seems to be a popular method to keep them from rolling off the table. Just like in your kitchen cupboard, the potatoes will begin to form sprouts. Plant them with the sprouts orientated the right way and you’ll see green shoots earlier than if you hadn’t chitted them first.
Chitting potatoes give the plants a head start
10. Build Birdhouses
Spring is around the corner and with it will be garden birds. You’re likely feeding them right now since many garden birds rely on our help for the winter. You can help them even more by building boxes for them to nest in. The video below shows how to make a simple wooden birdhouse but there are many different designs that you can choose. It’s a great activity for a rainy or snowy afternoon, and you could even paint them before installing them in the garden in March.
11. Garden planning
Lastly, plan your garden. What you’d like to grow, where you’d like to put it, and when you need to sow seeds. Browse seed catalogs and Instagram for ideas. Use a garden journal or online planner if you’d like, but organizing now will keep you on track in the summer. It’s armchair gardening at its best, and the perfect winter gardening task for days when it’s just too cold, windy ,or snowy to want to venture outdoors.
Spend time planning the garden and what you’d like to grow
12. Harvest Winter Veg
Many kitchen gardeners focus on growing summer and autumn crops. If you plan ahead, you can have leeks, brussels sprouts, kale, cauliflowers, beets, parsnips, and other vegetables to harvest through the winter. An unusual and delicious winter vegetable that I’ve been growing for some years is the New Zealand Yam (oca).
One of my other favorites is purple sprouting broccoli. The earliest variety begins cropping in December with others following from January to May. They’re part of the brassica (or cole) family and are fairly winter hardy. The family also includes many varieties of cabbage and kale grown to be harvested in winter. Many root vegetables are hardy down to 25 °F (-2.2 °C) too, so if you’re in zones 8-11, you can leave them in the ground until needed.
13. Sow the First seeds
Though you’ll need to hold off for most veg, some seeds do benefit from a very early start. Three of these include onions, chilis, tomatoes, and eggplant (aubergines). That’s because each needs a long growing season, and if you’re in a mild or cold climate, your plants might not have enough time to produce if you sow in spring. You can also grow salad greens and loose-leaf lettuce right through the winter. Indoors, they’ll grow with a grow-light set-up, and plants started at the end of summer will continue growing slowly in greenhouses and polytunnels. Here’s more guidance on the earliest seeds to sow.
Start off tender veg like tomatoes indoors
14. Order bare-root fruit bushes and trees
It’s not just strawberries that you can order bare-root. Add more perennial fruit bushes and trees to the garden in winter too. You can get apples, pears, currants, gooseberries, and more for a much better price if you order bare-root. They’ll arrive looking like dead sticks, but don’t worry, the plants are dormant and just waiting to break into bud and leaf. You can also order bare-root roses for edible flowers and handmade skincare.
In winter, many fruit trees, bushes, and even rose bushes are available to order and plant bare-root
15. No greenhouse or polytunnel? Get one
Gardening without a greenhouse is possible, but growing with one is a joy! My current greenhouse is a vintage model and came with our house, and I’ve had a heavy-duty plastic Palmram model before too. I sold it when we bought the new house and the new owner took it away on the back of a trailer. You can get a greenhouse from a specialist company, and I’ve seen many for sale on Facebook, eBay, and other places. Greenhouses, and polytunnels for that matter, come in various sizes and price ranges, but another option is to build one. My friend Barb and her husband built theirs from recycled windows and she shares how they did it in the video below.
16. Attend a Seed Swap
Think of all the seed packets you’ve purchased in your life. Have you used all the seeds or have had to throw some away? Seed swaps are a fabulous way to give them away and take other seeds home that you actually need. That way seeds don’t get wasted and you save money. These community garden events are popping up regularly these days and the one I organize has been going strong since 2011. If you can’t find a seed swap in your area, use my tips to start your own. It’s fun, and I guarantee that you’ll have more than a few people interested in coming.
Attend or organize a seed swap to save money on seeds
17. Clean your pots
If you think your greenhouse gets mucky after a gardening season, think about your pots, modules, and trays. It’s not “dirt” that you should be worried about, but bacteria, viruses, fungi, and pests. Give them a good scrub using these tips from my pal Stephanie at Garden Therapy.
18. Clean your tools
Most of us keep our tools in reasonably good condition, but aren’t disinfecting and oiling them throughout the year. Winter is a great time to wipe them down with alcohol, buff any rust off, and oil them with good oil. Some people use WD-40, but to keep it more natural use natural vegetable oil. Olive oil works and boiled linseed oil is a favorite since it dries quickly.
19. Tidy the Shed
While you’re cleaning your pots and tools, empty the shed and give it a full clean too. I recommend giving the Marie Kondo method a go here and have an entire piece dedicated to how you can use its principles in the garden.
Time to sort out your garden shed (ahem…hoard)
20. Sprout seeds
Homegrown greens can be sparse unless you have a grow-light system or warm greenhouse or polytunnel. There’s another way to get your greens though — by sprouting seeds. All you need is a large glass jar with a lid, water, seeds suitable for sprouting, and a little time to have fresh salad sprouts any time of the year. You can also sprout seeds in other containers, but jars are by far the easiest way.
Sprout seeds in jars for fresh winter greens
Greenhouse gardening in winter: What to grow?
Winter growing is achievable because most cool-season plants can stand the near-freezing temperature. You can start with cool-weather vegetables and allow them to grow throughout the serious winter. So don’t just stare at those seeds and let’s start planting!
There are sturdy onion varieties that can be successfully planted even when the greenhouse is unheated. Below are some of the varieties to consider.
- Shakespeare is a white onion variety that can be relied on to grow during the winter.
- Electric is an excellent red variety.
- Radar provides an appealing yellow-colored variety.
If you live in an area that experiences milder winter weather, planting peas directly to the ground and close to each other will give you larger quantities. One of the best pea varieties that have been proven to withstand the cold is Meteor.
Winter greens sweeten with the cool weather. Here are some examples of the healthiest cold-tolerant leafy winter crops to grow.
Lettuce favors the cold weather. It is an excellent fall and spring vegetable that can even survive the coldest climates.
The hardiest of all kale types are the Siberian types which are soft and possess a softer taste than other kales. True Siberian type is great because it keeps on offering leaves all winter.
Cold hardy herbs
Herbs enhance every meal. There are herbs that are sensitive to colder temperatures. However, some of the most often used herbs can actually grow in colder climates.
Parsley is the hardiest of herbs. It decreases its growth in wintertime and can sometimes survive without some protection.
Chives are so easy to grow that even kids can do it. Plant the seeds in a pot and place it in a dark place.
Rosemary is a perennial herb. It can be planted at any time of the year and is strong enough to protect itself against the icy cold weather. This herb can thrive completely all year round.
Mint is a flexible herb that will proceed to grow during winter. It is like a weed that grows wild and is challenging to get rid of.
Root crops are also great winter plant ideas. You can set aside most of these root crops in the soil and just dig them up when needed. Some wonderful root crops to plant include rutabagas, leeks, radishes, turnips, beets, parsnips, and carrots.
Planting broad beans during wintertime means young plants by the time early spring comes in. The best method is to plant them in beds inside the greenhouse. If the weather is still mild, placing the beds near the door means they can easily be seen and pollinated by bees.
Garlic comes in several varieties and planting them couldn’t be easier. They have a long growing season like onions.
Chesnok red is the variety to go for if you want to taste a fuller garlic flavor.
Wight Cristo should be the option if you want traditional garlic that is commonly used for cooking recipes.
How to Grow Vegetables in a Greenhouse
A greenhouse is a good way to grow vegetables even when the weather is too cold for tender vegetables to naturally grow. Greenhouses work by trapping solar radiation inside layers of clear material such as glass or plastic. The more layers of glass or plastic between the inside of a greenhouse and the outside world, the warmer the greenhouse. This means you can grow cold-hardy vegetables year-round and start tender vegetables well before the last average frost date for your region.
Space your plants properly so that there is adequate circulation between the plants. If you use raised beds, thin out weak and spindly plants as they grow. If you grow plants in containers, set each container far enough apart that air can pass freely between the plants. This will help deter sickness and diseases. You may wish to include a fan in the greenhouse to stir the air. Small and low-growing plants such as lettuce or radishes need less space between them than vines or tall plants such as cucumber or tomato.
- A greenhouse is a good way to grow vegetables even when the weather is too cold for tender vegetables to naturally grow.
- If you grow plants in containers, set each container far enough apart that air can pass freely between the plants.
Water the soil as it dries out. Most vegetables prefer soil that is the consistency of a wrung-out sponge. Examine each plant for signs of disease or pest infestation. Bacterial or fungal diseases can enter a greenhouse through contaminated soil or on plants or seeds.
Remove plants from a greenhouse that show signs of disease. Manage pests with traps, insecticidal soap, and natural repellents such as basil, marigold or garlic plants. Hand-pick pests off the plants or release beneficial insects such as ladybugs into your greenhouse.
- Water the soil as it dries out.
- Bacterial or fungal diseases can enter a greenhouse through contaminated soil or on plants or seeds.
Pollinate vegetable blossoms to ensure that the plants produce vegetables. Tomatoes and peppers are self-fruitful. To pollinate them, tap on the plant to release pollen. Pollinate cucumbers, melon or squash by transferring pollen from male blossoms to the flowers of female blossoms with a paintbrush.
Add mulch around the bottoms of plants to help reduce evaporation and reduce the frequency of watering.
Different vegetables grow better in different temperatures. For example, tomatoes grow best in temperatures between 55 and 90 degrees Fahrenheit, while lettuce needs temperatures between 45 and 73 degrees Fahrenheit. At higher temperatures, lettuce will bolt, while tomatoes will not set blossoms well if the temperature falls below 55 degrees Fahrenheit. Keep greenhouse temperatures at a range optimal for all plants in the greenhouse. Monitor greenhouse temperatures with a digital thermometer. Add a heater if the greenhouse will not naturally stay warm. Vent the greenhouse by opening a door if the temperatures jump too high.
Temperature (of the soil) is a major factor in determining plant growth. It controls the mechanism that allows minerals and nutrients to be absorbed from the soil. Greenhouses are heated passively by the infrared radiation that comes naturally off the sun, and typically insulated to minimize heat loss from convection (the greenhouse is sealed up, to keep drafts down). This passive heating is often enough to provide sufficient heat for growing in the winter months, even in the colder zones 5/4/3 for growing those vegetables that can tolerate some cold. In these climates, heat-loving vegetables will likely require some sort of supplemental heat. A greenhouse will also typically have some vents or windows to allow air to ventilate once the ideal temperature is exceeded. There are automatic controls for this, but two vents with a fan if necessary will likely get the job done with much less complexity and cost. Supplemental heat in the winter can be achieved with a standard electric heater, but remember it is more efficient to heat only the soil by using some sort of heat mat made for that purpose. Greenhouses aren’t nearly as well insulated as even an old house, so the energy required to heat a greenhouse could be significant.
Tips for Vegetable Greenhouse Success
Watch out for fungal and other diseases that can grow on the greenhouse plants. Bugs may also get into greenhouses consult your local garden store or extension service on the types of insect repellents, fungal cleaners and fertilizers to use. Because fungi spread, you may need to separate or destroy diseased plants.
Plan the use of the greenhouse before buying or building, whether for year-round gardening or extending the harvest season by a few weeks. If you are attaching your greenhouse to your home, be aware that brick walls may absorb up to 35 percent of the sun’s heat. If you are building a pit greenhouse, plants can be sowed directly into the soil. Depending on the type of vegetable greenhouse your are using, watering systems may be available for purchase and installation.
Do not place your outdoor greenhouse near shade trees. Disposable milk jugs, if you use to hydrate your garden, must be monitored for leakage. Finally, glass greenhouse window coverings can break, and plastic greenhouse window coverings can tear. With some pre-planning, you protect your greenhouse and reap a long vegetable harvest from your greenhouse garden.