At What Temperature Can Frost Damage Your Plants? (With Table)

Maintaining your yard is a big undertaking, especially if you live in an area with varying temperatures. Knowing when to start worrying about protecting your plants from the cold can take time and effort.  

Frost can begin to damage your plants at 36 degrees Fahrenheit (2.2 °C) or lower. Different plants have different tolerances to frost. Some plants can survive a harsh winter, and others start to sustain damage as soon as they encounter frost. 

In the rest of this article, I’ll discuss when you should start worrying about frost damage to your plants. I’ll also explain which plants are frost-resistant and how you can protect your plants from the cold. Let’s get to it! 

Frost Damage Can Occur at 36 Degrees Fahrenheit (2.2℃)

You may think you don’t have to worry about frost damage until temperatures get in the double digits, but this is incorrect. Technically, frost is the layer of ice that forms on surfaces at 32 degrees Fahrenheit (0℃) or lower, and some plants start suffering from frost damage as soon as that layer of ice forms. 

However, frost can form at temperatures as high as 36℉ (2.2℃) because the ground gets colder than the air that your thermometer measures. If the soil gets cold enough to freeze, frost will form, even if the air doesn’t feel freezing. 

However, some plants can get damaged even before freezing temperatures. This damage has a lot to do with which parts of the plant you expose to the harsh weather. 

For example, a plant’s root or bud is much more susceptible to damage than the stem or the branches. Roots should remain safe and warm in the ground, so if you expose them to frost, they may not survive. 

For this reason, plants just about to bloom and then exposed to a late frost usually don’t bloom at all that season because the buds get too damaged. 

Other factors influencing how much frost damage a plant can handle include the following: 

• How long the frost lasts. Some plants can tolerate a few minutes or hours of frost, but if the freeze lasts more than a day, they’ll suffer significant and sometimes irreparable damage. 
• The type of plant. Some plants are more capable of handling colder temperatures than others. These plants usually have internal protection that evolved from their native climate zone. 
• The plant’s age. If a perennial plant is well-established and has been thriving in the area for some time, it’ll likely survive a harsh frost. However, if the plant is freshly planted and young, it will need more infrastructure or strength to withstand the freeze. 

The following table outlines the temperatures at which you should start to worry about common landscaping plants: 

Different plants have different tolerances to cold temperatures—so it’s always wise to do your research. Take note of which plants are cold weather-resistant and which ones aren’t. 

When Should I Cover My Plants?  

It would be best to cover your plants when the temperature remains at 30℉ (-1.1℃) or lower for five consecutive hours. At this point, most plants will start to sustain frost damage. You can remove the covering in the morning. Check out my article about plant covers.

The most crucial part of protecting your plants is being proactive. To prepare the necessary coverings, you should know your area’s average first and last frost date.

If you know the average first frost date is approaching, pay attention to the weather forecast and cover your plants as soon as it has been more than five hours at a temperature below 30℉ (-1.1℃).

If you have sensitive annual, subtropical, or tropical plants, you can start covering them as soon as the temperature hits 40℉ (4.4℃) or below. Just be sure to remove the covering as soon as the temperature rises above that level. 

Once the temperature rises above 32℉ (0℃), you can remove the cover to allow your plants to access the sunlight they need.   

The following table outlines the average last spring frost and first fall frost for all fifty states in the United States. I’ve based these averages on the state capital, so double-check if you live far away from the capital, as the frost dates may vary. 

Knowing these dates is a great way to stay proactive and protect your plants from frost damage. 

Which Plants Are Not Affected by Frost?

If you live in an area with cold weather, you might wonder what your options are for landscaping. It can be extremely frustrating to invest time and energy into a plant only to have it die from frost damage, so it’s best to choose cold weather-resistant plants from the get-go—so you don’t have to go through that heartbreak. 

The following plants are popular landscaping choices that will most likely survive the frost: 

• Lily-of-the-Valley. These beautiful flowers seem like they’d be delicate in cold temperatures, but that’s not the case. These flowers are freeze-proof and can survive in nearly every soil and climate.
• American Mountain Ash. This small tree is popular for landscaping, and its native environment is mountainous. Therefore, it can handle high levels of frost without any damage. 
• Evergreens. Evergreen plants are an excellent choice for people who live in cold areas. Most evergreens can survive in freezing temperatures if you add a layer of mulch to prevent them from getting too dry. 
• Coneflower. Coneflowers come in many colors and grow tall to stand out in your yard, and wide varieties are incredibly hardy. 
• Pansies. I’m not sure why people call other people “pansies” to be rude–these flowers are tough! They can survive cold snaps and single-digit temperatures for as long as a day. Pansies are a great way to go if you want a pop of color in your yard, even in the winter. 
• Columbine. Columbine plants only live a few years but are hardy and can survive frost. They also reseed easily, so even though they don’t last very long, they’re still self-sufficient for a long time. 
• Hosta. This popular plant is a perennial that can withstand frigid temperatures. The big, green leaves are a delight throughout the winter.
• Sedum. Sedum plants thrive in scorching and frigid temperatures. They’re also drought-tolerant, so I recommend sedum plants if you live in an area without much rain.    
• Peonies. Peonies come in several colors, so pick your favorite and plant them in your yard for color throughout the winter. 
• Siberian Cypress. These plants are native to the freezing mountains in Russia, so they’ll be able to live through frost. Their fluffy green leaves are a delightful addition to any yard. 
• Fastigiata. This spruce plant has blue-tinted needles, making it a gorgeous winter plant. They can survive cold temperatures, are drought-tolerant, and withstand intense heat. 

If you’re concerned about frost damage, I recommend using these plants for your landscaping because of their durability and ability to survive in cold and freezing temperatures. 

How To Protect Plants From Frost 

If you want plants in your yard that aren’t necessarily frost-resistant, you can! You’ll have to take the time and effort to protect them from the frost. Annual plants that bloom in warm temperatures are most likely to die from frost damage. Here’s what you can do to protect these plants: 

• Move the plant indoors. This option is only viable for a few landscaping plants, but if you have a plant you can pot and move inside, you should do so. Simply moving the plant into your garage is often enough to prevent the frost from getting to it.  
• Use a plant cover. You can make plant covers of various materials, including burlap, cardboard, cotton sheets, and more. These covers need to protect the plant from the frost and trap heat from the soil—so the plant doesn’t freeze to death. I recommend reading my article on the best plant covers for winter for more information.  
• Use frost cloth. Frost cloth is a plant cover that protects plants from frost damage. It comes in various thicknesses, so you’ll need to make the best choice for your plant’s health. For guidance, check out my article on how thick frost cloth should be.  
• Add a layer of mulch. Adding an extra layer of mulch to your garden bed adds the warmth and protection the plants need in cold temperatures.  
• Cover plants with a cloche. A cloche is a bell-shaped glass or plastic cover that you can place directly over plants to protect them. I like the Remerry Garden Cloche Clear Bell Covers from Amazon.com because the cloches comprise a quality plastic material. The ground securing pegs are heavy-duty metal, so they’ll last a long time. I also like that the domes have adjustable vents.   
• Wrap tree trunks. Trees are often too big to be covered by a cloth or cloche, so I recommend wrapping the tree trunk with towels, burlap, or rags. 
• Water your plants consistently. Well-watered plants are stronger and more capable of withstanding frost damage. Additionally, moist soil stays warmer than dry soil. 

By taking these steps, you can stop the frost from killing your precious plants and continue enjoying them for future seasons. 

Conclusion

Frost can start to damage your plants at temperatures as high as 36℉ (2.2℃). The damage a plant will endure because of frost depends on the type of plant, which part of it is exposed, and how long the frost lasts. 

Certain cold weather-resistant plants can survive a frost, and there are various ways you can protect more delicate plants from frost, including being aware of the average frost dates in your area.