Protecting your plants during frost

Damn that Beast from the East! Let’s fight it with all we’ve got. I’ve been doing a lot of research concerning frost and its effects on plants, but quite in particular how to protect your precious plants against the freezing temperatures.

Beagle in the snow animation

What’s the deal?

Plants can survive quite a bit, but once freezing temperatures fall upon them, it might come in handy to have an arsenal of tips and tricks to help them out.

The main problem with frost is desiccating! Plants won’t be able to hold or get the water they need. This is what happens when temperatures drop below freezing point:

  • Plants protect themselves by concentrating solutes in their water which can lower the freezing point up to -6°C (20°F).
  • In its defense against the cold, plants will try and remove water from its cells to avoid crystal formation inside. Needless to say their roots will stop absorbing water. This leads to the plant’s drying out.
  • With very low temperature drops, -6°C (20°F) or lower, ice crystal formation inside the plant’s cells can cause grave internal, sometimes irreversible damage.

Also don’t forget the natural process a plant goes trough under somewhat “normal” weather conditions. (Dry) winds and winter sun, though not as strong, will dry out your plants.

The effect of colors

Do not underestimate the power of dark colors and their ability to absorb energy. White reflects light, whereas black absorbs all of light’s wavelengths, converting it into other forms of energy, like heat. That heat will then be emitted into the environment.

So if we refer back to the garden, darker soils will contain more heat than lighter soils; another great benefit of adding humus (compost) to your soil. The blackness of your soil will absorb more light/heat and release it during the colder, sunless periods of the day.

Ice and cold

Water vs air

There’s a difference between water and air when it comes to holding and releasing warmth. The heat capacity of water is higher than that of the air. This means it takes longer for water to heat up. But it also means taking longer for water to cool down; or in other terms: give of heat. You can use this physical opportunity to your advantage.

Fill some water containers (jerry cans, jars, bottles …) to the brim with water. You can either fill them with hot water or you can let them heat up in the sun during the day. Mind you, the darker the container, the faster it’ll reach high temperatures and the hotter it’ll get. Once temperatures outside start dropping again, you can put them next to your precious, most beloved plants.

Watering your plants

Knowing that water holds warmth longer than air and the fact that plants tend to dry out during frost, it’s only logical to water your plants before frost. Water them before temperatures drop below 0°C (32°F). After sunrise, but before noon seems to be the best period of time. Temperatures will still be rising and the plant will have all day to absorb the water they need. Also as the soil surrounding your plant is moist, it’ll take longer for it to cool down.

Wet your plant’s roots, not its leaves!

Covering your plants

Covering up your plants can help protect them against the sun’s drying out but also against cold, dry winds carrying away all heat while they blow past the plants. Another thing not to forget is that wet plants are more vulnerable to frost than dry plants because the water on their leaves might freeze, causing damage.

Umbrella on plant

Here are some material you can use to do the job:

  • Burlap
  • Bubble wrap
  • Row cover
  • Old bedsheets
  • Cloche
  • Upside down pots
  • A tower of leaves

Mulching your plants

If you provide an extra layer of mulch around your plant’s roots, it’ll work as an insulation layer, retaining the soil’s warmth and keeping away the cold. You can build this layer with organic matter you have laying around (leaves, bark, wood chips, branches …)

Happy safekeeping!

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