Winter is not a great time of year for our trees mainly due to the harsh weather conditions. Our trees will try and protect themselves by going dormant, but often this may not be enough and we will have to add some extra protection to make sure they make it though.
Not all trees will need to be treated the same way so it is important you understand what you are actually trying to protect it from, which I will go through here.
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Do We Need To Protect All Trees Over Winter?
I think it is important to realise that not all trees are the same and not all environments are the same, which means the level of protection needed can vary from tree to tree and person to person.
Just because I do something a certain way does not mean it will be the same for you and your trees.
This therefore means that we all need to assess our own gardens and our trees individually to make sure we are giving each tree the protection it needs to survive.
What Are We Protecting Are Trees From Over Winter?
There are 3 main problems that your tree can face over winter, which are Cold Temperatures, Rain and Animals. I will go through this all in more detail, but basically you need assess each of these to see how much risk they are in your garden.
Cold Temperatures
Cold is the most obvious risk over winter. I am quite lucky and live in a fairly mild climate and it barely goes below freezing, but I know some of you experience some extreme levels of cold.
Basically when anything freezes it usually expands, this can be a problem for your tree as it can cause the cells inside to swell and then burst. This will of course kill those cells, which in turn damages that area of the tree. If enough of the tree is damaged in this way then it will die.
Bonsai trees are pretty small and delicate and extreme cold may be too much for some of them as they can easily get frozen to the point where they are damaged.
However, trees will naturally try and protect themselves from the cold by storing sugar in their cells. When a tree goes dormant it pulls all its resources into its core and fills its cells up with sugar. This makes the individual cells have a lower water percentage, which makes the harder to freeze.
Basically sugar syrup will need a colder temperature to freeze at than water so the tree can handle colder than normal temperatures. It’s a very clever system the tree has, but that doesn’t mean it’s perfect so we may need to still protect some trees.
You will need to find out what temperatures you trees can survive in and then evaluate if they can survive in your climate or not.
You find out more about by this reading – What Are Cold Hardy Bonsai Trees? – where I explain how to see how much cold your tree can handle.
Water (Rain)
We often overlook the risk of excess water in winter, but for some of us, it is the wettest time of year. Too much rain isn’t really the problem it’s the other factors around it that make it risky.
The trees are dormant at this time of year so they are not using the water and as its cold there is less evaporation than there would be at other times of the year. This means water may stay in the pot longer than you want.
Normally excess water can drain out of bonsai pots, especially when you use good soil …However, the problem is that a lot of trees will have filled their pots with roots during the growing season and the soil may have broken down or just generally be too full of roots and may need repotted. This can all negatively affect the soil and its drainage ability.
This could mean you now have a combination of poor drainage and excess water which can be a recipe for disaster and is why we may need to step in and protect our trees.
Cold and Water Combined
Too much water in your pot actually changes how your tree can handle the cold. Water will of course freeze and expand which most trees can cope with. However if there is a lot of water, then it can be a problem.
Every time the water freezes it expands, so if there is a lot of water in the pot and it’s all expanding it is much more likely to cause damage.
This is probably more of a risk for me, where it is quite wet and occasionally freezes and thaws again throughout the season. This repeated expanding and contracting can really wreck the roots and the composition of the soil. If you live in an area where everything freezes at the start of winter and then stays frozen solid until spring, it’s probably going to be less of a problem.
Animals
Animals struggle to survive over winter and if they are not hibernating then they may be looking for food, which could mean your tree is on the menu. It will depend on what animals are in your area along with what species of trees you own, but there is always a risk that animals will have a little nibble on your trunk.
This can certainly make the tree look ugly which is not what we want, but it can also potentially kill the tree if they damage it enough, so it is worth considering this risk and then protecting your trees from it if you feel like it could be a problem.
(You can read more about – How To keep Squirrels, Birds and Other Animals Out Of Bonsai Pots)
Working Out If Your Tree Needs Protection
To work out if you need to protect a tree or not, you need to firstly understand what tree you have and then what conditions it is going to face.
Really you need to understand each trees hardiness level as well as find out what hardiness zone you live in. You can then compare the two and see if your trees are suitable for your garden and if they need protection or not.
(You can read how do this in more detail by reading – Working Out How To Over Winter Bonsai Trees)
You should also evaluate the trees general health and current conditions. If a tree has any sort of health problems or is a very shallow pot you may need to give it more protection than a tree that is really vigorous or growing in a large pot.
How To Protect The Tree
I actually have a much more in-depth article on how to do this and where you should actually put your trees, but the short answer is that you need to move your trees to give them some shelter.
(This is the more in depth article – How To Protect Your Bonsai Trees Over Winter)
How much shelter they need will of course depend on their ability to handle your local climate. The less they can handle it, the more shelter they will need.
It is also important that you don’t go over the top and give your tree too much shelter; you just need enough to take the edge of things and allow them to get through the winter without the risk of dying.
Other Problems That Might Occur
While sheltering will usually protect your trees, they are not always problem free and other issues can occur. These are usually less severe issues compared to not being sheltered, but it is still worth knowing what can happen.
Watering
Water is still important over winter and if you are sheltering a tree then it will reply on you for the water.
the first thing you need to remember is that your tree is not growing over winter, so it will not need fertiliser …but you may still need to water it, but the reality is you will not need to give it much.
I find the colder temperatures and rain usually keep everything damp enough so that you don’t need to water. However, if you have moved you trees in a shelter where they are not getting rain then you will need to check more often. You cannot ignore you trees completely just because they are dormant.
I have actually found that the trees I keep in the shed do not need watered as everything stays damp and never really dries out. I still come and check every now and as it is extremely important that they do not dry out as this will kill them.
Mould
As the trees stay damp for a long time, as well as potentially having less airflow around them (if they are inside an unheated shelter), this means mould can happen.
I find that the trees I keep in the shed always get mouldy. I know mould prefers warm damp places, but you will find it seems to like cold damp places too.
I often find mould on my soil, trunks and main branches. This can be avoided with better airflow, but I usually find that just cleaning the mould off at the end of winter is easier. I just brush it off with a toothbrush that is dipped in vinegar and that seems to kill everything and there is no long term damage.
Conclusion
Hopefully now you can understand what we are trying to protect are trees against during winter.
Everything in bonsai is done for a reason, so just blindly trying to protect a tree when you have no idea why is not very sensible.
Now all you need to is make sure you have read the other articles I have about this topic so how to know if you tree actually needs protection by finding out how hardy it is and then how to actually protect your trees.
Working Out How To Over Winter Bonsai
How To Protect Your Bonsai Trees Over Winter
Hi, I’m Ian. I have been doing bonsai since 2014. I created this site to spread all the knowledge I have acquired over the years. Don’t forget to check out my Youtube videos where I show the progress of my own Bonsai each week or connect with me on social media.
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