As the temperature starts to drop from double figures into single digits, we all know it isn’t too long before winter really takes a hold. Whilst there’s probably a few people out there who welcome the colder months with open arms, the majority of us will be gripping onto the leftovers of summer and putting on several layers to delay the inevitable – putting the heating on.
Chances are your plants share your feelings towards winter. They much prefer the nicer weather with a sprinkling of rain; the last thing they want is freezing temperatures. Sadly, they don’t have the option of central heating or chucking on extra layers to stay warm like we do and that can lead to problems.
If you’ve ever wondered why a considerable amount of plants in your garden don’t survive the winter months, make sure you carry on reading and we’ll try to explain the problems plants face and how to overcome or prevent them.
How Much Cold Weather Will Kill A Plant?
Now one of the most pressing questions I’m asked is ‘how much cold weather or frost will kill a plant?’ and it’s quite tricky to answer as it depends on several things.
Firstly, the climate plays a huge role in it, obviously. If you have the joy of living somewhere that doesn’t see below freezing temperatures even in the coldest months, then you shouldn’t have much of a problem – in fact, the heat will probably be more of a worry to you than the cold. However, if you live somewhere that sees prolonged periods of double figure negative temperatures, then your plants are going to have a hard time surviving. For people in the UK reading this, we fall somewhere in between these extremes and have what is considered an ‘averagely cold winter’ which is mostly single digit negative temperatures.
Second of all, plants are different and each one has a different amount of resilience to cold weather. This is defined by the ‘hardiness’ of a plant and ‘hardiness zones’ which change dependent upon where you are in the country (more on this at the end of the article).
Thirdly, time is drastically important. Slightly related to the hardiness of the plant; some plants are able to withstands weeks or even months of extreme cold whereas others might only be capable of sustaining life for a few hours in such temperatures. As well as this, temperature fluctuations can also cause problems for plants. The UK is extremely bad for this as one minute we can be having a mild spring with plant buds opening; then the next day, frost and freezing temperatures!
All of these things will have an impact on just how much cold a plant can take; that’s why it’s so hard to provide a definitive answer since there are so many variables. Even with all of the information out there and a wealth of experience under your belt, some plants will still surprise you every winter without fail.
Why Do Plants Hate Winter?
It’s not so much that plants hate winter; it’s more the fact that they dislike the cold and freezing temperatures associated with this particular season. In all fairness, I’d probably hate weather that has the potential to kill me as well, so I can sympathize.
The main damage done in cold weather is down to freezing. Light frost doesn’t usually cause much damage (unless the plant is extremely tender); however, heavy and hard frosts can really cause problems since it damages the actual tissue of the plant. The problems occur as a result of water inside the plant’s cells freezing which results in dehydration and further structural damage to the walls of the cells. This damage is further compounded when the temperature increases and the plant defrosts far too quickly due to broken cell walls. Rapid defrosting can, and will likely cause the leaves and stems on a plant to die.
Not to forget trees either, they also struggle in winter with cold temperatures, especially the bark on younger trees or those with naturally thin bark. The problem with this is that it’s hard to identify any damage until spring comes around and cracks become visible. This is due to sudden temperature drops that occur at night after being exposed to sunlight during the daytime; these usually heal naturally without any help, however sometimes, your intervention may be required.
How To Save Frozen Plants
There’s good news and bad news when it comes to frozen plants. The bad news is that severe cases of frost damage are usually beyond repair and the plant has already died. However, the good news is that if it’s caught early enough or the extent of the frost damage is relatively minor, these plants can be saved and nursed back to full health.
When stems and leaves are damaged, you have the option to prune them away, but this isn’t always the best idea. If another cold spell is likely, it will be best to leave this dead foliage in place to act as a layer of protection or barrier to any further frost; this will keep the rest of the plant in better health! In some cases however it can be better to prune immediately, especially on plants which have soft stems as these are likely to rot through if left unattended.
Remember, if you prune plants back during the winter months make sure you can move them to a more sheltered location or even indoors if you have the ability. This will protect them from any more harsh frosts and give them the best chance of survival until better weather returns.
The rest of the time, you should leave the pruning of damaged and dead stems/leaves until springtime when warmer temperatures arrive and your plants are no longer in harm’s way. If leaves are damaged, simply prune them back until there are no visibly damaged leaves left on the plant. Stems are slightly different in that if they are still alive, you only need to cut away the damaged areas as they will eventually re-grow from where you left them.
However, if they are dead, cutting them back completely is the only option for the overall health of the plant. Remember to water when needed and apply fertilizer if required as this will be beneficial in the recovery of damaged plants.
If you notice cracks on your tree bark which haven’t healed naturally you may want to lend a helping hand. Cut away any bark which has been torn or is hanging off; remembering to be careful to avoid inflicting more damage. After this you can use a knife or something similar to smooth the edges of the bark & cracks; this will help the tree in forming a callous which will start it on its way to recovery.
Cold & Frost Prevention
To minimise the amount of damage that your plants incur over the winter months, there are some steps you can take as a precaution. As they say, prevention is better than a cure and this holds true when it comes to protecting your plants from tissue damage.
If the weather reports that cold spells are predicted, you can give your plants a bit of extra protection by wrapping them in burlap or covering them with a sack; whichever is more suited to the plants in question. This second layer will keep the majority of the cold out; however, when it heats up the next day, remember to remove them.
It may seem like a hassle, but if you’re serious about protecting your plants, this needs to be done. Potted plants can also be protected by simply moving them indoors or at least to a sheltered area which takes them out of direct sunlight and freezing cold winds.
Taking these preventative steps over winter will ensure your plants have the best chance of surviving with minimal or no damage at all!
Plant Hardiness
Plant hardiness dictates how well a plant will grow in certain temperatures and conditions. Hardiness ranges from ‘very hardy’ plants which are suitable for -20°C temperatures all the way to ‘tropical’ which need to be grown in temperatures exceeding 15°C.
The scale of hardiness ratings can be found at RHS.org.uk along with some examples of plants which are suitable for each rating level and temperatures. These ratings can then be compared to a map of the UK which allows you to see which zone your location falls under. This will give you an idea of what plants will be suitable for winter growth and which ones are more likely to struggle.
This post was originally published in December 2013.
