When Can Plants Be Moved to an Unheated Greenhouse?

Growing anything at all in an unheated greenhouse during the bitterly frigid winter months may seem like an unattainable goal. Being able to grow your own sustainable vegetables may seem absolutely ludicrous, but if that’s how you think, you are definitely wrong. Having the knowledge of how to use an unheated greenhouse, plus what plants are best suited for such an environment is the key to achieving positive results.

As long as you have the benefit of sunlight, there are quite a few methods you can employ in order to keep your crops warm enough to survive through the winter months. In fact, using an unheated greenhouse in winter will permit you to grow many hardy vegetables.

Along with greens such as spinach and lettuce, you can also grow cold- tolerant vegetables such as broccoli and cabbage in your unheated greenhouse.

However, tomatoes, green pepper, and chili pepper seedlings do not like the cold and should not be moved to an unheated greenhouse any earlier than April.

What Temperature Is Too Cold For A Greenhouse?

The average greenhouse needs to keep nighttime temperatures of 55 degrees F or higher, while the maximum temperature is normally around 90 degrees F during the day all year. Ideally, the temperature should be 90 degrees F during the day, and 75 degrees F for the night.

The greenhouse temperature for vegetables varies according to the type of crop you want to grow, but growing vegetables at lower or cooler temperatures at night generally produces better results.

Can You Start Seeds In An Unheated Greenhouse?

It is possible to start seeds in an unheated greenhouse providing you steadily keep to the lowest temperatures at which seeds can germinate. While minimum temperatures will allow seeds to grow, they will only grow quickly and uniformly at optimal temperatures.

Type of Plants That Will Grow In An Unheated Greenhouse

There are many varieties of leafy, green vegetables that can flourish in an unheated greenhouse. If you enjoy a good salad every now and then you’re in luck. Many types of lettuce are vulnerable to freezing but certain kinds, like radicchio and endive, are robust enough to endure the cold. Swiss chard and kale can also grow quite well under these circumstances.

Cabbage, spinach, and arugula are other selections for rugged plants that can survive an unheated greenhouse. Collard and mustard greens also grow excellently in an unheated greenhouse.

You can also try planting some sturdy, cold-resistant celery, broccoli, peas, or Brussels sprouts.

Suggestions For Good Winter Vegetable Growth In An Unheated Greenhouse

. In the same manner you would for an outside garden, you’ll have to be sure to space your vegetable plants correctly to get maximum growth.

. If you would rather have raised garden beds in your unheated greenhouse, be sure that you remove the weak vegetable plants as soon as they grow. This way, the sturdier plants have lots of room to thrive.

. Despite how cold it can become outside in the winter, the temperature inside an unheated greenhouse may be higher than you realize in the daytime. When it is very sunny outside, it can turn hot enough to cause some winter vegetables to experience stress. To prevent this from becoming an issue, be certain that there is lots of air moving throughout the greenhouse. Try opening the doors for extra ventilation if needed, or you could add a fan inside the greenhouse.

Monthly Guide For An Unheated Greenhouse

JANUARY

Plant carrots and radishes on the border of the greenhouse. Before you begin planting though, work some peat and a little fertilizer into the soil. You can also use grow bags if you prefer. The best manner to put down your seeds is to thinly scatter them about, and when they grow, thin out the seedlings as needed.

Saxa and French Breakfast are excellent types of radish to pick; Early French Frame and Rondo are great carrots for early planting.

You can sow spring onions in a like manner at the end of the month. Onions that are meant for growing outdoors should be planted in a pot or seed tray, apply a bit of warmth if you can, to help with growing, and then picked off one by one into small pots. March is when you should plant them outside.

It might seem strange, but January is also a great time to plant peaches. See to it that there will be free drainage by putting a covering of rubble or broken pots some 1.5 ft down.

FEBRUARY

Plant lettuces for later placing outside in March. Place the seeds in a pot or seedbed, picking them out one by one when the seedlings grow big enough so that they can be managed.

Plant peas that are early-maturing to be ready for transplanting in March or for continuing to grow if they stay in the greenhouse. You can plant the seeds in separate 2 in pots to reduce disruption when they are planted outdoors.

MARCH

Plant broad beans, leeks, peas, and quick-growing cabbages for planting outdoors when they become big enough.

APRIL

Get the greenhouse border ready for tomatoes, working in a large amount of compost or manure, and using a rake to work base fertilizer into the surface. Tomatoes should be planted at month’s end, placing the 1 1/2-2ft apart, and putting up support posts for them.

As the sun is now becoming stronger, proper ventilation is required when the weather is clear. Give the vegetable plants lots of water, and even dampen the surfaces of the greenhouse in the warm weather. Keep an eye out for any early indications of aphids and whiteflies, and act immediately to eradicate them.

Vines should be kept sprayed with water to nudge them into growing and expanding.

MAY

Tomatoes require routine watering and also feeding at this time.

Sweet peppers can be transplanted at this time. Place the pepper plants 1.5 ft apart. Cucumbers and melons should each be planted 2 ft apart, at the end of the month, providing support for them by tying them to wires that are fastened 6 in apart to the glazing bars.

Any new vine growth should be tied to wires and their tips pinched. If a shoot has no flowers it can be left to grow until it has nine leaves.

JUNE

Now you should make an effort to make sure that cucumbers, tomatoes, and melons are kept tied in or trained, whatever method is correct. Furthermore, there will have to be some shading applied to the glass to protect these and other plants.

Early beans and peas that were raised in pots in the greenhouse are now going to be ready to be harvested.

You must be sure and provide adequate ventilation and perform damping down often if the weather is hot and dry. For your tomato plants, spray them with water at midday to help the fruit to set.

JULY

By this time you should be harvesting your cucumbers and tomatoes on a regular basis to help make it easier for more fruits to grow. The tips of your tomato plants should be pinched out when 5 or 6 trusses of fruit are seen on the stems. You can let your cucumbers reach as much as 8 ft.

And since you don’t want your vegetable plants to develop powdery mildew, spray your vines every fortnight.

AUGUST

Not much to do right now except to continue to maintain the care of your vegetable plants.

SEPTEMBER

If you want excellent sweet peas for next year, now is the time to plant the seeds and transfer the seedlings to 30.5 in pots. Allow the plants to spend the winter in the greenhouse so that they will be ready for planting outdoors come spring.

For as long as the warm weather lasts, keep ventilating the greenhouse, but lower the amount of shading little by little.

OCTOBER

Now is when you should remove all of the shading from the greenhouse glass.

Also, pick the green tomatoes and place them in a dark, cool area so that they will ripen slowly.

Plant lettuces for spring cutting. Plant and pick them out in the normal fashion, then place them out on the border of the greenhouse.

NOVEMBER

Now is the time to bring your herbs that have been growing in pots inside to ensure a winter supply of wonderful tasting herbs that will season your food.

There may be some plants that are still a bit vulnerable, and you should have extra protection ready for these, like old newspapers or sacking.

If you have any vines, they should be pruned promptly once the last of their leaves have fallen off. This needs to be done to the extent that you have shortened the present year’s growth, eliminating all but one or two buds.

DECEMBER

Now is when you should clean the glass and framework of your greenhouse completely with household bleach for a disinfectant, but only if you are able to remove all of the remaining plants. Furthermore, to keep pests or diseases from carrying over, eliminate the remaining debris from summer crops, and the like.

Expectations

To avoid disappointment on your part, keep in mind that in the winter, vegetable plants and others will not flourish and grow as quickly as they do in the summertime. It might take certain plants a while to reach their full development, and you can’t force them to adhere to a schedule.

Some plants, especially in the months of December and January, won’t make any appreciable progress for several weeks. But don’t be concerned! In all likelihood they won’t die, and that means that they will become active again and resume growing, just as soon as the temperature is warm enough.

There’s a powerful sense of pride and fulfillment that comes from eating sustainable vegetables that have been grown in your own garden. Furthermore, harvesting and consuming fresh produce all year long — especially during the wintertime — is an incredible experience.

While it may seem extremely difficult to keep your growing season going through the winter, particularly if you are a novice gardener, the truth is that winter gardening is really quite easy. The key to being successful at this though is knowing how to grow your vegetable plants in an unheated greenhouse.