How to Cover Plants for Frost Protection - Wenke Greenhouses (2024)

FAQs

How to Cover Plants for Frost Protection - Wenke Greenhouses? ›

Bed sheets or comforters work best for covering large plants and shrubs. Newspaper can be used on low-growing foliage, but it can often be difficult to get it to stay in place. I have used old pillow cases, sheets, towels and even cardboard boxes.

The protection it provides will not only help you to keep tender plants frost-free - it will also let you grow hardy crops, such as salads and herbs, all winter. An unheated greenhouse can keep overnight temperatures as much as 5°C warmer than outside, which will keep plants frost-free in all but the worst of winters.

Cover Plants – Protect plants from all but the hardest freeze (28°F for five hours) by covering them with sheets, towels, blankets, cardboard or a tarp. You can also invert baskets, coolers or any container with a solid bottom over plants. Cover plants before dark to trap warmer air.

Do not use plastic, such as tarps or plastic sheeting to cover plants. Plastic will transmit cold air to the plants, causing more harm than good. We recommend using cotton fabric or frost cloth to protect plants from frost.

This is definitely not the best idea. Plastic or vinyl materials are normally too thin to provide adequate insulation and since they do not breathe, moisture can get trapped inside. If temperatures drop low enough, this moisture will freeze on your plants, causing more harm than good.

At the very least, invest in a propagator with electric bottom heat if you don't have one already (those with thermostatic settings will give better temperature control.) Even if you provide no other heat source, this will help keep vulnerable plants frost-free.

Insulate with bubble wrap

Use horticultural rather than packaging bubble wrap to insulate your greenhouse because it's stronger and is designed to withstand UV light. Look for big bubbles because these offer better insulation and also let in the most light.

If plants are not portable, do the following to protect them: Cover the plants with beds sheets, light drop cloths or blankets, row covers (frost blankets), burlap, cheesecloth, etc. Drape the covering over the plants like an umbrella.

Bring Plants Indoors

Bringing plants indoors is the easiest way to protect them from frost or freeze damage. Potted tropical and annual containers can be pulled into a heated room, porch, or into a protected and warm structure, such as a garage, to protect them overnight.

Plastic can be used to protect plants from frost, but it's not the best or most effective material. In fact, the horticultural experts here at Green Impressions actually recommend against it. Plastic materials such as vinyl and traditional camping tarps aren't breathable, causing moisture to get trapped inside.

Should I cover my plants at 39 degrees? ›

Once temperatures drop below 40°F, you may want to start covering your plants with a frost blanket depending on what you're growing, which we'll get into in just a bit.

I have used old pillow cases, sheets, towels and even cardboard boxes. Just be sure that whatever you use to cover your plant, the cover reaches the ground and traps the warm air inside the canopy. Plastic can be used but it is important to note that you should not let the plastic touch your plants.

Frost blankets are garden covers made of lightweight, 100% polypropylene fabric. Frost blankets are ultra-lightweight, keeping your plants safe from damage. Unlike commonly used alternatives like bed sheets, burlap, or painter's tarps, the fabric allows plants proper airflow.

Don't keep the coverings on your plants for more than two days in a row without removing them in the day since this can cause water to become trapped underneath, leading to fungal diseases and can cause plants to produce new growth that can be easily damaged by cold.

Moving plants indoors is the best protection. A covered porch usually provides protection from light frost, but the garage or sun room is better for freezing temperatures. A couple days in darkness won't hurt the plant. Or move them out during the day and back in at night, if cold temperatures persist.

Plants to move inside: Tomatoes, peppers, eggplant, and others that will not survive frost. Plants to cover: Potatoes, radishes, spinach, leaf lettuce, beets, mustard. Plants that do not need to be covered are onions, cabbage, broccoli, cauliflower, carrots, turnips, and kale.

Nearly all crops can tolerate an average temperature of 50° F, and cold-tolerant crops can handle temperatures of 35 to 40° F. The most cold-sensitive crops, such as basil, should not be held below 55° F.

On average, a greenhouse can be up to 30˚F warmer than the outside environment. However, this can vary based on the type and insulation of the greenhouse. What is this? For instance, a single-layer greenhouse might show a temperature difference of 5 to 10˚F, while a double layer can be around 9 to 14˚F warmer.

When can I put seedlings in an unheated greenhouse? It is best to germinate seeds in colder months so late winter through to early spring is ideal for germination. You can put seedlings in an unheated garden greenhouse when they are still tiny, such as when they are in their seed starting trays or pots.

Beyond storing solar heat, one of the most important things you can do is seal up all gaps and cracks in the greenhouse. Use caulk or weather stripping to stop heat from escaping, particularly around doors, joints, and vents. Once all gaps have been sealed, consider installing insulation.