Gardeners often worry about the threat of freezing temperatures and frosts that can harm or even kill plants and damage crops.
Here’s what you need to know to protect tender plants from extreme winter weather.
What Is Extreme Cold Weather?
A freeze occurs when temperatures drop below 32° F or 0° C. When the water inside a plant freezes, it can cause the plant cells to burst, resulting in irreparable damage.
Here’s how different plants react to extreme winter weather:
- Tropical and frost-tender plants: Cannot survive extreme cold so they only grow naturally in warmer climates.
- Annual plants: Can’t survive extreme cold, but they disperse seeds to replenish their numbers once the weather warms.
- Root-hardy perennials: The foliage is killed back by a freeze, but the roots survive in a dormant state until spring.
- Fully hardy perennials, shrubs, and trees: Enter a dormant state, which decreases vulnerability to freezing temperatures by reducing sap content and conserving water. Spring blooms and early foliage may be damaged by late-spring freezes, but the plants themselves usually recover.
What Is Frost?
Frost occurs on clear, still nights. As the air temperature approaches freezing, the surface temperature of plants can dip below freezing, causing ice crystals to form in the same manner that dew forms on warmer nights.
Because temperatures vary just a few feet above the ground, frost can form when your thermometer reads above freezing. Cold weather may or may not be accompanied by frost.
Types of frost include:
- Hoarfrost — the familiar feathery white frost you see on chilly mornings. It results when water in the air is deposited directly in the form of ice crystals.
- Rime — happens when water is deposited in liquid form through dew or fog, which then freezes. Rime has a glazed appearance.
- Black frost — a term used when frost didn’t form, but plants were nonetheless damaged (and blackened) by freezing temperatures.
Effects of Freezing Temperatures on Plants
For all but the most tender plants, it doesn’t matter whether the conditions produced a frost or a freeze. What’s important is how cold it got and for how long.
When temperatures near freezing, a few degrees can make a big difference.
To advise gardeners so they can take proper precautions, different terms are used to describe the severity of a freeze. This chart explains the various terms:
| Temperature | Type | Effect on Plants |
|---|---|---|
| Down to 28° F for a couple of hours | Light Frost, Light Freeze | Usually only harms very tender plants. Ice forms only on the outside of the plant. |
| 25-28° F for several hours | Hard Frost, Killing Frost, Moderate Freeze | Damages foliage and blossoms. Ice forms inside the plant, causing plant cells to burst. Will kill back root-hardy perennials and damage crops. |
| Below 25° F for several hours | Severe freeze | Extremely cold weather causes damage to many plants, mostly through desiccation (drying). |
The average first and last frost dates for a given area usually refer to the occurrence of killing frosts. These are most often caused by fronts of arctic air moving in and are more indicative of seasonal change.
Research has shown that most crops and plants can recover from brief dips below freezing, but when the temperature reaches 28° F it begins to cause extensive cellular damage and crop loss.
How to Protect Tender Plants from Frost or Freezing Damage
Cold weather is one thing, but if frost is predicted, you may want to take steps to protect vulnerable plants such as:
- Houseplants and tropicals
- Spring-blooming shrubs and trees such as azalea, rhododendron, and cherry
- Citrus trees
- Tender bulbs such as dahlia and elephant ear
- Warm-season vegetables such as tomato, corn and pepper
- Warm-season annuals such as impatiens, petunia, and geranium
Steps to take when frost or freezing temperatures threaten tender plants:
- Bring Indoors: Frost-tender plants in containers should be brought inside during cold weather. Dig up tender bulbs and store them in a cool dry place.
- Water Plants: Water plants thoroughly before a freeze to prevent desiccation and to add insulating water to the soil and plant cells.
- Protect Tender Sprouts: Cover tender plants overnight with an inverted bucket or flower pot, or with a layer of mulch. Be sure to uncover them in the morning when the temperature rises above freezing.
- Cover Shrubs and Trees: Larger plants can be covered with fabric, old bedsheets, burlap, or commercial frost cloths (avoid using plastic). For best results, drape the cover over a frame to keep it from touching the foliage. Fabric covers help to trap heat from the soil, so make sure your cover drapes to the ground. Uncover them in the morning when the temperature rises above freezing.
- Assess Losses: Hardy perennials, trees, and shrubs may recover from a late spring freeze, even if visibly damaged. Their blooms and fruit may be lost for the year, but once they begin actively growing you’ll be able to determine and remove any permanent damage to stems and branches. Frost-tender plants will not recover at all, so avoid planting them until you’re confident that extreme cold weather has passed.
- Practice Prevention: Choose plants that are hardy for your climate zone, or plant tender plants in containers that can be brought indoors. Avoid applying fertilizer until after the last frost, to prevent a flush of tender growth that can be damaged by the cold.
Further Information
To find the average frost dates for your area, check out:
Well done article. Watering your plants the night before is an interesting idea that I’ll have to try out.
Jeff
Can you tell me why my Spiny Bear’s Breeches didn’t bloom all last summer? What would cause this?
We planted two weeks ago, fertilizer mixed in soil because the soil had been struck by lightning and was not producing. Also, mixed new top soil and potting soil in rows. We have shoots and live plants, fruit trees and fruit shrubs were planted aswell. A cold front is predicted for here (childersburg, alabama) around easter. How can we protect so many? Should we spray heavy the day before? Help.
Excellent article on various types of frost and methods of frost protection. The temperature differentiation between light and hard frost was most helpful, as was understanding how the frost moves within the plants. Thank you.
We bought lots of used sheets to put over our garden when it freezes. Works like a charm. And cheaper then the “blankets” they sell for a small fortune.
Great info.. I live in Fl. and have a veggy garden right now I usualy put sheets over my veggies. It seems to keep them alive 🙂 I wrote to you a few months ago about my oak tree and all the baby (seedlings) that are sprouting all around it. It made it on your radio show . I was told to pull them out..That did not work. They are very deep roots. Any other way to get them out??
Goodenough I plased a sheet over my flowers…I was counting on that being enough. Signing Out Sincerely Regina
Getting ready to do battle with the freezing temps tomorrow night. Going to follow the suggestions.
I am a first time visitor to this site, and I find the information almost limitless. just scanning through the projects I have also found there to be so many helpful ideas and how-to’s. The information helps one to be self-suffienent and independent. The how-to’s helps one avoid many costly mistakes of the past.
Hi Julia,
Glad to hear you found our site and Julie’s article helpful.
Thanks for the feedback!
I have hydrangeas that have not bloomed. They have been planted for a couple years and still no blossoms.
Is there a Product that you can spray on outside plants during the winter season that would protect from Freezing..for potted plants not huge plants..prefer not to use sheets or blankets! Thank You..See a lot of info on internet but where to purchase? Thanks Fred Noble Portland Or 97225
Can Pine oil be sprayed on cedars in the fall as a anti desiccant .one drop in a gallon sprayed on the shrub thanks
I am moving in december from Quebec to Ontario. It will be freezing. What should I do to protect my plants, they will be for two days on the truck?
Thanks.
I have bamboo with loads of small branches. I cut these off, put each end in the ground over tender plants and the cover these hoops with sheets and sometimes even add a sheet of plastic over the sheet to protect plants for wind. Seems to work really well. I sometimes also
add a string of mini christmas lights, not led as they produce no heat, and this also helps to keep tropicals from freezing.
Can flowering bulbs I planted stand 34 degrees and many have already popped up?
I have perrenials planted on two terraces that have survived 8 winters, even when covered with snow plow pile up. This year in Wisconsin we have had one deep freeze after another. Covering my terrace gardens now is @ 6 ft. of solid ice and the ground is frozen deep down. Flooding is expected. Will my perrenials/bulbs survive? Thank you.
Going down to 0 with the windchill- 14 degrees. Will covering plants even help?
It will help, but not with just a light covering. It will also depend on the types of plants. First, make sure they are well watered. Next if you have any christmas lights that are NOT led, plug those in and string around the plants, next add a few supports to hold coverings. Anything that you can push into the ground or pot at about 12″ intervals. Now first cover with sheets, old blankets, or other pieces of fabric. Make sure it is long enough to drop to the ground. Now put a piece of visqueen or plastic drop cloth over that and place something heavy on all of this to keep the wind from blowing it of. This is where the supports will be crucial. Hopefully this will work. Water is vitually important to keep the roots from freezing. The lights, whether christmas or any other non-Led will help and securing the covering to the ground will prevent wind burn. Good luck, it sounds tedious but just gather everything and go for it.
We have a tall (approximately 13 ft) Rubber tree plant. We raised it from a cutting, so it’s our baby!!! We live (don’t laugh) in Southern CA. no wait listen, it’s supposed to freeze for the nest couple of nites…So pleeeeze tell us HOW TO PROTECT IT???
Helpless in So CA.
a week or so after i planted vegetable seeds in a raised garden bed, we got several nights of below freezing temps. If nothing has sprouted above the surface, will the frost effect the newly planted seeds?
I water my garden with a misting line over all plants. Should I leave it on to prevent 30 degrees freeze?
Great suggestions for protecting plants from frost. I am going to try.
In answer to non sprouting vegetable seeds being damaged by frost. I live in zone 3b. No problem if the seeds have not sprouted. I put my seeds in on May 14th and had frost last night, May 17th. May get frost again before June. The seeds will germinate when the soil temperature is around 20 degrees C. Have tomato plants in the back window for now and will put them out first week in June to be safe.
we just moved from Tennessee to Florida and there is a hydrangea planted in front of the house that gets full mid to late day sun. Most of the upper leaves are burned and it hasn’t bloomed since we moved in July 1. Should I move this plant or build a shield for it for protection from the hot florida sun? I keep it watered and it looks healthy other than the sun burned leaves
I have some rare plants, which will not survive the cold temperature here in SC, I have planted them in the planter on my patio, can I protect them from frost by covering them with bedsheets, should I double layer the sheet? Do I have to uncover my plants time to time during cold weather? Also can I put them in my garage, they will get minimum sunlight though? Once I brought them inside the house and there were eggs laid by lizard and they hatched in the warmth of the house and I had huge problem later with those pesky little creatures. Pl. advise the best option for my plants
I live in Victoria Australia
thank you so much for the information on frost for my new plants it is very helpful
kindest regards Judy
What about potted annuals that can’t be brought inside?
Can they be covered …
. . . and left on a concrete patio?
. . . and left on a wooden deck?
. . .and placed on the lawn?
Which of those options is the best?
Is it advantageous to put them adjacent to the house? And if so, how does that factor in? For example, is on a concrete patio placed adjacent to the house likely be better than placed on the lawn away from the house?
Thanks!
Cardboard boxes are excellent for protecting plants. Just wrap the cardboard around the plant to block the wind and secure it with binder clips or sturdy tape. Cover with blanket or sheet.
Do you uncover them during the day
I planted 6-7 days ago some seeds will they die in – 2 degrees as I really do hope not
How about a tarp if it is a field of crops.
I think you should do fields and crops
1. I gave the plants on the porch front porch water yesterday because they need it. One of them is drooping I noticed it before I gave them water I’m not sure if it is the cold weather that got to it or not. The reason I had didn’t cover it was is because I don’t know what kind of planet is and if it can survive the cold or not. What can I do to get it to pyrkup? It has in the 30s here in North Carolina. 2 of the plants came from the funeral home in Louisiana.
Hi, Tanya,
Gardening questions can be tricky since the rules can change based on the region. We would suggest contacting your local Master Gardeners association.
Master gardeners train on a range of topics so they can provide advice, at no charge, for people in their area.
Here’s more information: http://www.ncstategardening.org/extension_master_gardener/index.php
Thanks for your question, and good luck!
My Peach tree did not produce any peaches last year it may have gotten frozen. One thing that continues to grow is a green fungus. I sprayed but no luck I pick some of it off but it grows bigger. How can I get rid of the fungus?
Hello
Every year, due to climate change and snow, we lose our hazelnut products in the spring and unfortunately no solutions have been presented so far. Please advise if you have any suggestions. Karimi . Iran
Hi, Farshid!
We’re opening this question to the TodaysHomeowner.com community.
Any ideas, y’all?
HEY! B.Stratton you misspelled a few words but no worries kiddo:) I can help with the spelling LOL! I had the same question so if you get an answer PLEEZE write back to me THX!;)
signing off Barbra Lynn
I had put my 6 pepper plants outside yesterday ,it was a nice e sunny day temp 66F.left them out for the night and this morning they had yellow leaves and looked dead.was that from the sun or the night temp.43F
Hi, Sara,
Gardening questions can be tricky since the rules can change based on the region and climate.
You didn’t include the location, so we suggest contacting your local Master Gardeners association.
Master gardeners train on a range of topics so they can provide advice, at no charge, for people in their area.
Thanks for your question, and good luck!