How To Grow In A Greenhouse During The Winter?

Winter greenhouse gardening is a great way to extend your growing season and enjoy fresh produce throughout the colder months. With the right knowledge and proper conditions, you can grow many winter-hardy vegetables and fruits, such as carrots, beets, scallions, leeks, winter lettuces, spinach, arugula, mache, kale, and parsley.

Niki’s top 10 favorite crops to harvest in winter include carrots, beets, scallions, leeks, winter lettuces, spinach, arugula, mache, kale, and parsley. If micro-greens are desired, stick to cool-tolerant crops like peas, kale, cilantro, mustard greens, arugula, and collards.

A small greenhouse can provide the perfect environment for growing winter-hardy crops in cold climates. Winter hardy plants like Galleon cauliflower, mustard greens, spinach, green onions, or leaf lettuce thrive in increasingly cooler fall and winter greenhouses.

Spinach, kale, claytonia, mache, arugula, mizuna, tatsoi, bok choy, lettuce (good to about 15f), parsley, and cilantro seem to thrive through winter. Many varieties are good at tolerating winter’s cooler temperatures, such as kale, spinach, and Swiss chard. Salad leafy greens can also be grown in winter greenhouses.

Some plants may not do well in an unheated greenhouse in the middle of winter, such as citrus, tomatoes, corn, and beans. By choosing the right plants and adjusting the conditions, you can ensure your greenhouse remains a productive and healthy space for growing winter-hardy crops.

What is the cheapest way to heat a greenhouse?

Gas heating is the most cost-effective option for greenhouses, with an average efficiency of 80 percent due to heat loss through exhaust ports. Open flame heaters emit ethylene gas, which can affect budding plants and cause depleted oxygen levels in newer greenhouses. Gas heaters with a flu and power exhaust are best for greenhouse applications, but they need a hole punched into the side of the greenhouse for exhaust.

Electric heating is the most efficient, running at 100 percent efficiency, but it is expensive and may not be suitable for many gardeners’ budgets. Passive solar heat can offset some of the cost associated with electric heating, and 240V units are recommended for greenhouse applications. For 120V units, avoid infrared heaters or heaters that transfer heat to objects instead of heating the air. Oil-filled radiator-style heaters are the best inexpensive 120V heaters for greenhouses, which can heat small hobby greenhouses during winter months when placed near a fan.

Passive solar heat collects heat from the sun’s radiation during the daytime and releases it into the greenhouse during the nighttime. This is usually done with water or other thermal mass that can absorb and hold heat for a duration of time. One technique is to line the north wall of a greenhouse with black water containers, which absorb light and heat that passes through the greenhouse to the north wall.

When the sun sets, the heat held by the water slowly dissipates into the greenhouse environment. When combined with electric heat, passive solar heat can significantly reduce the annual cost of heating a greenhouse.

How many hours of sun does a greenhouse need in winter?

A greenhouse needs at least 6 hours of sunlight daily to maintain warmth. However, after 10 hours, plants may dry out, necessitating the use of a cooling system. The type of plants grown affects the required amount of sunlight. Light-loving tomatoes require 6-8 hours, while lettuce needs 4-6 hours. Full sun benefits plants by enhancing photosynthesis, which converts carbon dioxide into oxygen. Sunlight is not just an energy source, but a lifeblood for plants, ensuring their survival.

How can I keep my greenhouse warm in winter?

Winter greenhouses can help grow fresh, tasty vegetables at home during colder months. These greenhouses provide a safe and controlled environment for growing vegetables, allowing homeowners to enjoy the health benefits of homegrown produce. Some ways to heat a winter greenhouse include adding thermal mass, using a germination mat, using a horticultural fleece, trenching, using hotbeds, using black 55-gallon barrels, using electric room heaters, and using hot water heating systems. These greenhouses can also be beneficial for those living in colder regions.

Are greenhouses safe in the winter?

Maintaining a night minimum temperature of 4º or 5ºC is crucial for protecting plants from severe snap frosts. For budget-conscious heating, horticultural fleece can be used to cover vulnerable plants during cold spells. Soil-warming cable is an economical heating system that provides heat to the roots, ensuring their survival even if top-growth is damaged. It is safe, easy to install, and allows for accurate temperature control.

This system is particularly useful for young plants during cold times. The performance of the system depends on the cable type, prevailing temperatures, and installation. Covering plants with fleece or translucent sheeting can help retain heat.

How can I make my greenhouse colder?

To ensure proper greenhouse ventilation, open doors to allow more air in, and use natural ventilation instead of fans. Open weave interior shade screens can also help. A greenhouse ventilation system should provide cooling, humidity removal, and air mixing. To check systems before hot weather arrives, maintain fan ventilation by checking fan belts for wear and tension, cleaning fan blades, and lubricating shutters. Direct air circulation fan flow by directing all HAF fans to blow from shutter end to fan end, sealing cracks, and closing doors.

Save energy by staging fans using two stage thermostats or an electronic controller. Choose NEMA premium motors with an efficiency of 86, which use 8 to 10 less electricity than older standard motors. Clean insect screening by spraying water from the inside or vacuuming from the outside to remove dust, leaves, and insects that may block tiny pores. Ensure there is enough screen material to prevent overheating.

Use evaporative cooling to lower the greenhouse temperature to several degrees below outside ambient. Portable evaporative coolers have been effective for some growers. Maintenance on fan and pad systems involves keeping the pad clean of dirt and debris. Reduce algae by flushing or bleeding off some water and adding an algaecide. Nozzle clogging on fog systems from chemical and particulate matter can be controlled using rain or treated water.

What temperature is too cold for a greenhouse?

To maintain optimal plant growth, keep your greenhouse temperature below 3C (37F). Tender plants like pelargoniums, half-hardy fuchsias, and citrus trees prefer a minimum of 7C (45F), and safest at 10C (50F). This temperature is ideal for young plants and plug plants. If you have a conservatory, use it to overwinter delicate plants. Position heaters carefully, placing them in an open, central spot away from water and angling the heater to prevent foliage desiccation by direct airflow above nearby plants.

How to winterize a greenhouse?

In order to winterize a greenhouse, it is necessary to repair any damaged panels, reinforce the caulking and sealing, inspect the heating system, drain any frozen pipes, clean the entire greenhouse, insulate with bubble wrap, set up circulating fans, and place plastic sheeting around any plants that are susceptible to frost.

What not to grow in a greenhouse?

Greenhouses are ideal for gardeners as they provide controlled environments that extend growing seasons and protect plants from harsh weather. However, not all plants thrive in enclosed spaces. Some common mistakes to avoid include large trees and shrubs, which can outgrow containers and damage structures. Invasive plants, such as mint or certain ivy species, can quickly overtake other plants and become difficult to eradicate once established in a greenhouse.

To avoid these issues, it is recommended to reserve your greenhouse for compact or easily pruned plants. Additionally, plants with high temperature requirements, such as long-lived perennials, should be kept outside for easier control. By avoiding these common mistakes, you can save time, effort, and disappointment in your greenhouse gardening endeavors.

How do you keep the temperature constant in a greenhouse?

To ensure proper temperature control in indoor grow rooms, it is crucial to properly size your HVAC system, have enough heating and cooling capacity for greenhouses, install horizontal air flow (HAF) fans, use shade curtains during high-light and high-temperature months, and measure temperature correctly.

Sizing the HVAC system is essential for indoor grow rooms to handle the heating and cooling loads that come with growing plants. Having enough heating capacity for greenhouse production is essential for winter conditions and summer weather, as it helps maintain desired growing temperatures.

Hybrid air flow (HAF) fans are essential for distributing temperature evenly throughout the crop and breaking up microclimates around leaves for better gas exchanges and controlling powdery mildew. Avoid “dead air” zones within rooms or greenhouse zones, as fans located too high above the crop do not provide enough air movement within the crop and can adversely affect moisture levels.

Shade curtains should be used during high-light and high-temperature months, typically designed for 30 to 50 light reduction and closed during the brightest and hottest hours of the day. If there is no retractable shade curtain inside the structure, whitewash can be applied over the greenhouse roof until fall weather approaches.

Measuring temperature correctly is also important for growth, as average daily temperature is the most important measurement for growth. Leaf temperature can be measured using a digital infrared thermometer to determine when to close the shade curtain.

Can you grow in a greenhouse in the winter?

A modest greenhouse is an optimal structure for cultivating winter-hardy crops in frigid climates, offering an ideal environment for horticulture during the cold season. It is possible to ascertain which winter vegetables are suitable for cultivation and to gain an understanding of the methods required to maintain the requisite warmth.

What happens if greenhouse gets too cold?

Freezing injury is a condition where plants are exposed to temperatures below freezing, causing damage that is more noticeable after a day or two of warmer temperatures. This injury can occur at temperatures above freezing and as high as 54° F. Common symptoms include water-soaked lesions on leaves, bronzing or browning of leaves, and wilting. More severe chilling injury can result in stem and leaf collapse. Young plants, including plugs and cuttings, are more susceptible to low-temperature damage than mature ones.

Some cold-sensitive crops develop temporary symptoms, such as pale green or yellow-green leaves at moderately low temperatures. Freezing injury is more obvious, with tissue dying and turning brown or black. Rooted plants can recover from mild to moderate chilling damage, but affected tissue may need to be removed and additional production time may be needed. It is generally best to dispose of and replace young plants with chilling or freezing damage.