Can You Cover Plants With Plastic Bags for Frost Protection?

When overnight frost threatens delicate plants, gardeners often turn to makeshift materials like plastic bags for protection. But is covering plants with plastic bags an effective safeguard against freezing temperatures? Let’s take a closer look at the pros and cons of using plastic covers for frost protection in your garden.

How Plastic Bags Impact Plants During Frosts

Plastic bags and sheeting can provide some insulation against freezing air. The plastic traps heat escaping from the soil to create a warmer microclimate around your plants. However, effectiveness depends on several factors:

• Thickness – Thinner plastic provides minimal insulation Thick plastic sheeting or multiple layers work better,

• Air pockets – Plastic wrapped directly around plants retains less warmth than creating a tent to trap air.

• Contact – Plastic touching plant tissues can worsen freeze damage as moisture condenses and freezes on leaves.

• Wind – Flapping plastic loses its insulating ability. Weight down or secure plastic covers.

• Duration – Plastic works for overnight frosts of a few hours, not multi-day deep freezes.

So plastic can provide some degree of frost protection, but it has limitations. Preventing plastic contact with plants is crucial, as is providing adequate insulation for extended freezing conditions.

Best Materials for Protecting Plants from Frost

While plastic bags can work in a pinch, other materials are better suited for insulating tender plants:

• Fabric sheets – Light bed sheets are soft, breathable, and trap heat effectively.

• Frost blankets – Spunbond fabric blankets designed for cold protection allow air flow.

• Burlap – Coarse open weave protects while preventing moisture buildup.

• Newspaper – Multiple layers provide surprising insulation from frost.

• Towels/blankets – Especially for smaller potted plants that are easy to wrap up.

These materials cradle plants gently while sheltering them from frigid air. They allow some ventilation so condensation doesn’t build up. And since they conform to plants’ shapes, layers can be added in colder weather.

Creating Quick Cold Frames for Added Protection

To amplify the warmth around covered plants, construct mini cold frames as insulation barriers:

• Use boards, bricks, bales of hay, or other materials to form walls around plants.

• Cover the walls with fabric sheets, frost blankets, plastic, etc.

• Weight down covers along the top of the walls to seal in heat.

The dead air space within a cold frame provides significantly more frost protection. Low walls also shield plants from wind, preventing covers from blowing away.

Inexpensive kits are available to assemble DIY cold frames of varying sizes as well. These extend the season for frost-tender plants.

How to Safely Use Plastic for Protecting Plants from Frost

Plastic bags can be made to work if precautions are taken:

• Avoid contact between plastic and foliage which can worsen freeze damage.

• Support plastic sheets above plants with hoops or frames so plastic doesn’t touch.

• Place black plastic on ground to absorb heat from the soil.

• Weigh down plastic securely so wind doesn’t blow it away.

• Use thicker clear plastic or double bag for more insulation.

• Add additional covering like burlap or newspaper over the plastic layer.

• Monitor temperatures and remove plastic during daytime to prevent overheating.

With some ingenuity, plastic can help buffer plants against light frosts. But tissues in direct contact with plastic remain vulnerable, so maintaining an air gap is key.

Ideal Alternatives to Plastic for Protecting Container Plants

For potted plants, plastic is not the best frost remedy. Here are smarter options:

• Place pots together and cover as a group – Draw pots close to conserve heat and cover en masse with blankets.

• Insulate pots – Wrap pots in burlap, towels, or other materials before covering plants.

• Bring plants indoors – Moving potted plants into a garage, greenhouse, or bright indoor area avoids cold damage entirely.

• Use cold frames – Mini cold frames around each pot amplify warmth retention.

• Provide heat – Place strings of outdoor-safe lights under benches of potted plants for warmth.

Since plastic bags don’t insulate entire pots, it’s better to use other materials to protect the roots in the soil as well as the plants. Grouped pots retain more heat to buffer against plunging overnight temperatures.

Emergency Frost Protection in the Absence of Other Options

While plastic should not be your first choice for protecting plants from frost, it can serve in an emergency if other solutions aren’t available:

• Drape plastic sheeting or open trash bags over plants without allowing contact. Use stakes and hoops to prevent touching leaves.

• Wrap smaller plants in multiple layers of plastic, securing it at the base.

• Double bag for better insulation.

• Place containers of warm water near plants to radiate additional heat.

• Remove plastic first thing in the morning once temperatures warm.

When faced with imminent frost and no alternatives, anything is better than leaving plants exposed. Just take care to minimize direct contact between plastics and foliage. Once the cold event has passed, identify improved solutions for future protection.

Key Takeaways on Using Plastic Plant Covers

To summarize key points on covering plants with plastic:

• Avoid direct contact between plastic and foliage which exacerbates freeze damage.

• Other materials like burlap, blankets, and commercial frost blankets are preferable.

• Create a tent or air gap, don’t wrap plastic flush around plants.

• Use plastic sheets or plastic-lined cold frames to trap rising heat.

• Weigh down and secure covers firmly.

• Check for and prevent condensation buildup during daytime.

• Remove covers first thing in the morning as temperatures warm.

• Improvise emergency protection only when alternatives aren’t available.

• Insulate roots by grouping and covering entire containers.

With smart usage, plastic can buy a few degrees of cold shielding. But when it comes to insulating and protecting vulnerable plants from frost, plastic should not be your first line of defense. Use it judiciously and only when dire circumstances call for quick emergency action.