What Temperature is too Cold for Plants

What Temperature is too Cold for Plants?

Most gardeners across America ask what temperature is too cold for plants to know what care to give their plants as the weather changes.

In general, most plants need warm temperatures to thrive. Cold temperatures are an enemy to the progress of growing plants.  However, what temperature is considered too cold for plants?

This question has various answers because it all depends on the plants you have in your garden.

A rule of thumb is usually anything below freezing which is 32 degrees F, but sometimes even this can be too cold for some plants.

Cold temperatures not only affect the outdoor plants.  Many houseplants originate from the tropics or in semi-tropical areas. The cold temperatures are likely to cause them damage too.

What Help Do Gardeners Have?

The United States Department of Agriculture offers a map showing annual extreme minimum temperatures for different locations across the U.S.

Gardeners should use this map to understand if the plants they are growing or want to grow will survive in their areas.

The USDA map is broken down into 13 geographic zones and shows the sub-zones. Look for your zone by entering your zip code on the site or clicking on your state.

For example, if you live in Ohio, go to the USDA hardiness zone map and enter your zip code.  Enter the captcha code provided to help prove that you are not a robot.  Your hardiness zone will appear at the top – zone 6a with winter temperatures that can dip down to -10 to -5 degrees F.

If you wanted to grow a hardy plant like begonias, you would find that they can do well in zone 6a, but you will have to protect them from frost.

Zone maps are not absolutely accurate, but they give closely related information. Some plants grow well in a zone but might not be indicated on the map or vice versa.

Other conditions that exist in your particular area can affect your plants.  It’s important to research before growing a particular plant to learn the quality of soil, amount of moisture, and humidity your plant will need.

plant hardiness zone map

What Temperature Is Too Cold For Plants?

Many of the plants grown across America originated from the semi-tropical or tropic regions.  If they are exposed to cold temperatures, they can easily die or get damaged.

The right temperature to cover or protect your plant from cold varies from plant to plant.  Let’s look at some different categories of plants to know when they should be protected.

Blooming houseplants.  These can include tillandsias, begonias, bromeliads, and more.  They are best grown at average room temperature, with the summer ranging from 65 to 75 degrees F while the winter is at 60 degrees F. Most of these plants do not tolerate cool temperatures.

Ferns.  Both the tropical and indoor ferns do well in average or even cool room temperatures. At night, they like temperatures ranging from 60 to 65 degrees F but do not like it below 50 degrees.

Succulents. These desert and cactus-like plants can handle warm temperatures during the day and cold nights.  They can tolerate temperatures as low as 40 degrees.

Effects of Cold In Plants

Too much cold negatively affects plants.  Many start to show signs of cold damage when frost catches up with them.  Some signs include

  • Plant wilting
  • Leaf discoloration
  • Black foliage
  • Droopy leaves
  • Loose root ball

Cold affects plants by freezing their cells.  This causes damage and interrupts the water and nutrients pathways to flow to where the plant needs them.  In small branches and twigs, the living xylem is much more affected by the cold than big branches.

The lack of water and nutrients causes the plant tissue to be dormant, resulting in tissue death and blackened stems. The effects of the cold in outdoor plants are noticeable, showing signs of hardened plants.  The damage of cold shows also in early spring. This happens when a warm period is encouraging new growth, and a sudden freeze appears.  The temperature adjustment is a big factor that affects plants, especially when the plants break dormancy with the warm weather setting in only for the cold to set in again.

How to Protect Plants From Frost?

The first and foremost thing to do is choose plants native to the area or hardy specimens that can adapt to the climate.

When planting in your garden, try to get some shelter from the wind, snow, and sunlight.  To protect your root zone, apply mulch around the base of the plant.

If you live in an area with unpredictable weather patterns, invest in a frost barrier that you can place over sensitive plants, trees, and shrubs.

If you have a plant that you are not sure can survive in the cold weather outdoors, plant in containers.  This will enable you to bring it inside when all the danger of the frost has passed and then set it out on the patio.

Bring potted plants inside

In the summer and spring, months put your potted plants outside on your porch or patio and bring them in during winter.  However, what is the right time to bring them in?

Hanging baskets and potted plants should be placed indoors before the temperature reaches below 45 degrees F at night.  Inspect the plants you intend to bring indoors for damage, insects, or diseases.  Aphids, mealy bugs, or other pests multiply quickly when brought into the warmer indoors.  Treat any diseases and deal with pests before bringing in the plants if necessary.

If you bring a flowering plant into the house, set it in a window facing south or place it under glow lights.

Don’t be overly concerned if you notice some leaf drop in some plants you have brought indoors.  They will time to adjust to the new conditions.  Once inside, do not fertilize your plants for two to three months.

Covering outdoor plants

If you cannot bring your plants indoors, then you will need to cover them to protect them from cold.  Use black-colored plastic to cover your plants, not a clear one.  The reason is sunny days; the clear plastic must be removed as it will create a greenhouse effect on your environment.  Black plastic reflects the sunlight so that you can leave it on during sunny days.

Besides the plastic, you can use cardboard boxes, but they could get wet and soggy, forcing you to change them over a short period.

Whatever you use, be sure to anchor it to the ground using bricks or rocks to keep it firm to the ground.

Frost Temperature For Plants Conclusion

If your plant suffers from cold damage, it does not mean it is going to die.  You can still move it to a warmer area and give it time to recover from the shock and adjust to the new surroundings.

Nevertheless, you can save your plants early before the cold hits them.  Generally, September starts to prepare for the cold months ahead.