For most of North America, it is the time of year when temperatures are starting to drop as the fall season starts to creep up. As soon as the leaves start to turn brown and yellow it is time for us to start focusing on our business’s outdoor plants. How do we protect our exterior containerized plants from cold damage?

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Cold damage to exterior plants occurs primarily in two ways: The first way is through desiccation (water loss). The second is through cold damage to plant tissue. Cold damage to plant tissue is highly dependent on the cold-hardiness adaptability of each plant type. Coconut palms don’t thrive in Detroit for a reason! Each type of cold damage is discussed below.

What is desiccation?

Desiccation is caused in several ways in cold winters: dry soils, frozen soil/water and water loss from high winds. Although plants do not use as much water in the winter, they still uptake water continuously, even in the coldest times of the year. This is especially true for evergreen plants (plants that retain their leaves in winter such as spruce, junipers, rhododendrons, hollies, etc).

You can best protect exterior plants from desiccation by keeping them well hydrated. When temperatures are above 40°F, check soil moisture and water if needed (be sure to avoid over-watering). When temperatures are consistently warm in fall and winter, take advantage and keep the plants hydrated. Avoid watering when temperatures are below 40°F or when sustained freezing temperatures are expected within 24 hours as this water will freeze and not be available to the plants.

Evergreen foliage can also be protected from excess water loss using anti-desiccant sprays. These sprays are sold at most garden centers. They work by reducing water loss from the foliage. If you use an anti-desiccant, be sure to read and follow the directions. Although anti-desiccants can help, they are not a substitute for keeping the soil hydrated.

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Cold damage to plant tissue

When planning for an exterior installation, it is important to keep a few things in mind.

  • The southern and eastern sides of a building are better protected from harsh winter winds. These winds typically blow from the north and west. If plants will be exposed to the north or west, select tougher plants. You should always select exterior plants suited for your cold-hardiness zone.
  • Plants can be protected from cold damage and desiccation using a barrier consisting of mulch like straw, wooden stakes and burlap. However, this may not be possible due to the appearance of the barrier. You may want to temporarily sacrifice the plant’s exterior appearance to sustain the plant during harsh cold temperatures.
  • Some plants can be moved to warmer or better-protected locations if feasible.

What temperature is too cold for plants outside?

The answer to this question differs across plant types. Sanseveria, for instance, is a pretty tough plant species, able to withstand temperatures as low as 40°F. Conversely, a Pothos plant does not do well with temperatures under 65°F. There is no universal temperature for all plants that is too cold, so that is why it is important to do your research. However, it is safe to say if living in an environment with harsh winters and temperatures below 20°F, it is always wise to bring plants indoors during this time, if possible.

What is the frost temperature for plants?

Frost will usually develop on plants when the ground temperature falls below freezing, which is 32°F. Strong winds are also able to make the effect of the frost and damage to plants worse.

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How to protect plants from cold damage

Make sure your plants receive adequate watering in the summer and fall months before winter temperatures set in. This will prevent them from going into colder months under drought stress and keep them from drying out quickly. When temperatures start to drop, plants should be watered in the daytime before the late-night freezing climate takes over.

Although it may tempting to prune brown and damaged-looking foliage on a plant that has suffered from the cold, it is best to hold off from doing so. Pruning too early can kill the plant from the trauma of freezing. Your Ambius specialist knows exactly how to plan for these conditions and will help to transition your plants to the next season.

Always use exterior plants suited for your cold-hardiness zone. At Ambius, our exterior landscaping experts are able to work with you to determine what plants will work best for your external environment. Contact your local Ambius office today if you are interested in enhancing your building exterior with containerized plants. Our designers will discuss your needs and the vision you have for the exterior of your building.