Why plastic damages plants

Why Plastic Can Damage Your Plants During a Freeze

By Todd Farber, Aggie Horticulturist

When a freeze is in the forecast, many Houston gardeners scramble to protect their plants, and one of the first materials they grab is often plastic. While it might seem like an easy and effective option, using plastic as a freeze covering for Houston gardens can actually harm your plants rather than help them. Let’s break down why this happens and what you should use instead.

The Problem with Plastic

1. Plastic Traps Moisture

Plastic is a non-breathable material, meaning it holds in moisture. When placed over plants, the moisture in the air condenses on the inside of the plastic. As temperatures drop, this moisture can freeze directly on the plant’s leaves, stems, and buds. This creates frost damage—the very thing you were trying to prevent!

2. Plastic Transfers Cold

Unlike breathable materials, plastic doesn’t insulate well. Instead, it allows cold air to pass through and can even amplify the cold if it comes into direct contact with your plant. Leaves touching the plastic are at high risk of frost burn.

3. Heat Trapping in Daylight

During sunny days, plastic coverings can trap heat beneath them, causing temperatures to rise dramatically under the cover. This quick fluctuation between daytime heat and nighttime freezing can stress plants, sometimes more than the freeze itself.

4. Lack of Ventilation

Plastic doesn’t allow airflow. When left on for extended periods, it creates a closed environment that fosters excess humidity. This can lead to mold, mildew, or even suffocation of the plant.

What to Use Instead

If you want to give your plants the best chance of surviving a Houston freeze, ditch the plastic and try these materials instead:

• Frost Cloth or Row Covers: These breathable fabrics are designed to protect plants from frost while allowing moisture and air to escape. They’re reusable and provide a layer of insulation.

• Burlap: A natural, breathable material that helps insulate plants without trapping moisture.

• Old Sheets or Blankets: These household items work well in a pinch, especially for larger plants or shrubs.

Tips for Proper Covering

• Support the Material: Use stakes or a frame to keep the covering from touching the foliage. Direct contact can still cause frost damage, even with the right materials.

• Secure the Base: Anchor the edges of the covering to the ground with bricks, rocks, or stakes. This keeps cold air from seeping underneath.

• Remove Covers During the Day: When temperatures rise above freezing, uncover your plants to allow sunlight and air circulation.

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A Final Word of Advice

As an Aggie horticulturist, I’ve seen my share of plant damage caused by improper freeze protection. Plastic might seem like the quickest solution, but it can do more harm than good. Stick to breathable materials, and you’ll give your plants the best chance to thrive even in the toughest winters.

💚 For more tips and detailed advice, check out our guide: Winterizing Your Garden with Todd Farber

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Written by Todd Farber, Aggie Horticulturist. Helping Texans grow better gardens one season at a time!