How To Protect Bonsai In Winter And What To Avoid

How To Protect Bonsai In Winter

Think of bonsai and likely the first thing that comes to mind is pruning and cutting your tree on a nice warm spring day. Sadly for most of us, six months of the year require us to actively take care of our bonsai during the harsh winter months as we prepare for the upcoming season. One of the things I really struggled with then, when it first started my journey in bonsai was exactly how to protect bonsai in winter? 

To protect your bonsai during winter, place your tree in a wood frame, or styrofoam box. Fill your box with mulch such as leaves, bark, soil, or fill with insulation until your pot is covered. Finally Invest in a wind guard to protect against dehydration and ensure your soil is permeable. 

So what exactly is the science behind why you should protect your bonsai during winter? And which method works best? Keep reading to find out more!

How to protect bonsai in winter?

Easily one of the scariest moments for any new bonsai owner is managing their first winter. After all, everyone always talks about exciting stuff such as pruning or beautiful designs but leave out the absolute fear that you have not known if your trees will survive or not. 

With the majority of bonsai trees being suitable for outdoor conditions, we must take into consideration exactly how to look after your bonsai during the winter months. 

The good news is that I’ve successfully managed to make my bonsais stay with me over the past few months and so I found that the following steps work best: 

  • Understand how cold your climate gets in winter
  • Use a wood, plastic, or styrofoam box to protect your bonsai from the elements 
  • Place your bonsai in your box carefully
  • Fill your box with mulch or insulation 
  • If using a wooden frame as protection, ensure you invest in a wind guard 
  • Ensure your soil is permeable enough so that your pot and roots don’t freeze
  • Practice mindfulness and patience until the spring

Let’s explore these in more detail

How To Protect Bonsai In Winter infographic

Understand how cold your climate gets in winter

The first step to winterizing your bonsai tree is to understand exactly how cold your tree will get. 

For example, I live in the UK where typically most winters won’t get much colder than -10 degrees Celcius. 

As such, the methods I’ve laid out will work for most temperate climates similar to mine. 

Now say if you are based in northern Siberia the steps you will take will often need to be a lot more drastic to protect your bonsai tree. 

For example, one of the methods I will talk about later is keeping your bonsai in a box.

In countries and places where temperatures get much colder than -10 degrees celsius then you may need to consider using more insulation or thicker boxes, or better yet, keeping your bonsai in a temperature-controlled greenhouse. 

If you are on the other end of the spectrum in a country where your winters are very mild or you have the same temperature year-round, it is likely your bonsai will not need to be winter protected at all. 

Understanding then, exactly what a typical winter looks like for you will set you up for success going forward. 

A good rule of them to follow is around 6 weeks to one month before the worst of your winter should be when you start making these preparations to winterize your bonsai. 

Use a box to protect your bonsai in winter from the elements 

The next step of protecting your bonsai from the harsh winter months is to simply put your bonsai in a box or shielding of some kind. 

The main purpose of this is to create a barrier between your bonsai and both the temperature and the elements outdoors. 

I found that the following three items usually work best: 

  • A styrofoam box 
  • Wooden frames
  • Plastic sheeting/netting 
  • Hay bales 

Styrofoam box

Styrofoam boxes are a fantastic option due to their insulating properties and ability to survive tough elements. 

To use a styrofoam box, cut off or remove the lid of your box and place your bonsai in. 

My recommendation for a styrofoam box would have to be the Polar Tech Styrofoam Box ( link takes you to Amazon) which should be large enough to keep two bonsai but also regulates temperature incredibly well. 

Now for those of you in colder environments or fear that the rainwater might just reunion your styrofoam box (I live in the UK, trust me, this happens… a lot) consider investing in a water cooler. 

The exact same thing can be done here – simply take off the lid and place it in your bonsai. 

My recommendation then for a water cooler or chill box would have to be the Cubix Ice Chest ( link takes you to Amazon) which comes in a variety of colors and finishes. What’s even better is that this lid is foldable meaning that you don’t necessarily need to remove it when placing ion your bonsai. 

Wooden frames

If you do not want to use a solid box or just have too many bonsais that you need to protect, another fantastic option would be to surrounding your bonsai with a wooden frame. 

Ensure that this frame is 6 to 12 inches high and that your bonsai fit right in the center of your frame. 

You will also want to invest in a wood that is waterproof so solid hardwood works best. For my recommendation, check out this cherry lumbar (link takes you to Amazon) which comes in a variety of sizes. 

Just keep in mind that if your bonsai is on the larger side you may need to drill a free of these together to ensure that the wall of your frame is high enough o keep your bonsai protected. 

Plastic sheeting or netting 

Another great and cheap option to help is to use waterproof sheeting or netting to protect your bonsai. 

However, keep in mind that this option works best usually only when paired up with keeping your bonsai in a box or a wooden frame. 

Simply drape over your plants to ensure any unwanted snow or rainfall does not damage your plants too much. 

Whilst a lot of your might already have waterproof sheeting at your disposal a great option would be the Xpose Clear Poly Sheets ( link takes you to Amazon) which can be used for many different purposes and is also weather resistant. 

Hay bales

Finally, if you are interested in a natural option, consider using three or four hay bales to protect your bonsai. Simply create an area in your garden wide enough for your bonsai and surround with hay bales ( link takes you to Amazon). 

Just be warned however is more difficult and extreme winters may not be the best option. 

Also, be prepared to have a lot of winter animals take refuge in your hay spot 

Place your bonsai

So you’ve decided on the type of box or frame that you want to keep your bonsai in, the next step, (and trust me it’s an easy one) is to simply place your bonsai inside. 

The only confusion here comes with how high the walls surrounding your bonsai need to be. 

Simply put, ensure that the walls surrounding your bonsai go as high as or just under the top branch to ensure maximum protection for your tree. 

Fill your box with mulch or insulation

Time to get your hands dirty… 

So once your bonsai is inside your structure of choice, the next step is to cover your bonsai and its plant pot in mulch or insulation. 

Your plant pot must be completely covered to avoid your soil from freezing. 

Now there are loads of items that work well for this but if found that a mix of materials usually works best

A good option then would be to mix up dry soil, pine leaves, and mulch in an evenly split mixture and then cover your plant. 

Now if you want to save some time (and a lot of mess) check out the Rubberiffic rubber mulch bag (link takes you to Amazon) which is my recommendations which works particularly well for bonsai trees in winter and as a natural insulation

Invest in a wind guard 

If you do decide to opt for the wooden frame options as opposed to a box, one additional item you may need to look into is investing in a wind guard. 

Wind you see can severely dehydrate your plants in a phenomenon known as wind scorch with even every green tree bearing the brunt of this. 

To avoid your leaves from permanently drying out or causing unnecessary damage to invest in a wind guard. 

My recommendation would be the Barton Fire Pit (link takes you to Amazon) which works partially well at blocking out harmful gusts and also doubles up as a fire guard. This wind guard is also a fantastic option as it about the right size as most average Bonsais

Ensure your soil is permeable 

Next up your soil. 

We need to ensure that your soil is protected on two fronts.

Firstly ensure that the top solid of your bonsai is evenly covered with your mulch of choice to best ensure that any ice cannot form directly on the soil potentially causing your pot to freeze. 

Secondly, it’s important the soil you use in your bonsai is permeable. 

This is so if any moisture does build up in your soil or water does get through, it can easily pass through your tree without freezing in the process. 

Practice mindfulness

Finally and arguably the most difficult part of how to protect your bonsai for winter is just to practice patience. 

Whilst it can be tempting to keep track of how your bonsais are getting on or move them to a warm location, the truth is that plants and even evergreen species go through natural cycles of bloom and decay, meaning that the winter is a natural part of bonsais process. 

After all, some bonsais species grow in very cold climates naturally such as pine breeds, and withstand the snow during the winter months – so I’m sure your garden will be fine!

Can you keep your bonsai inside 

I know what your thinking, why can’t we just move our bonsai trees inside during the winter months, won’t that solve our problem? 

Moving your bonsai trees indoors during the winter months will be problematic as the majority of bonsai trees are from temperate species (like Chinese Elm), which thrive better outdoors than indoors. Leaving these trees indoors causes a sudden change in temperature which can damage your plant. 

There are, however, exceptions to this rule. 

Some bonsai species, particularly those from the Mediterranean such as Pistaciaprefer a warmer climate year-round so keeping these in a temperature-controlled garage during the winter months work best. 

However you need to be careful, in the winter months it is not uncommon for indoor bonsai trees to develop excess mold and white powder – to read more about how to deal with this check out my post here. 

If you plan on moving Mediterranian trees back into the garden in the spring months then it is important that you ease them back in, exposing them during the warmest parts of the day and then keeping them away during the cold mornings and evenings. 

Which bonsai plants can you keep indoors? 

Whilst most bonsai plants work best outdoors there are a few breeds that can survive year-round indoors should you prefer to avoid winterizing your bonsai altogether. 

These are mainly tropical and semi-tropical varieties that should be kept away from the cold in most instances and so make for ideal indoor bonsais: 

These include: 

  • Chinese Elms 
  • Jade
  • Ficus 
  • Fukien Tea
  • Pomegranate
  • Serissa 

The science behind winterizing your bonsai trees 

So a lot of you are likely wondering exactly why we need to protect some bonsai species during the winter. 

In winter, all plants and trees go dormant as a way to protect themselves from the harsh climate – even evergreen trees. 

They essentially pull back all the chlorophyll from the tree as a way of protecting themselves – it’s why trees go yellow and brown in autumn. 

As most bonsais have a hard time adjusting to temperature, with the majority of mainstream bonsais on sale being imported recently, we must try to mimic the winter conditions from where the plants we purchased originally came from. 

This typically means protecting certain species that are in need of help. 

What to avoid when winterizing your bonsai 

Whilst winterizing your bonsai is an important step for a lot of us every winter, it can be very easy to over-winterizing your bonsai. 

This can typically be done in the following ways: 

  • Protecting larger bonsais from winter – usually larger bonsai trees in larger pots will need less protection from the elements 
  • Remove the cold altogether from your plant – Bonsai trees need protection but they still need the cold. Removing the cold for a bonsai during the winter months may mean it starts to flourish thinking it is spring. 
  • Stopping the pattern of freezing and thawing – It is important to stop the nightly event of the freezing following by thawing in  the morning regularly, even if your Bonsai is protected, allow your bonsai to freeze once or twice to get the signal that it is time for winter and then move into protection mode 
  • Not taking your plant breed into account – All plant species are not created equal so thinking that your bonsai will be fine in the winter without doing your due diligence is important 
  • Forgetting to water – wWilst your bonsais may get enough water from the snow the truth is you should still water your bonsai and more specifically the mulch surrounding it once every two weeks as a minimum – this will; also give you ample time to inspect your bonsai and see how it is getting on. 


This post was written by Fehed Nicass who has been passionate about bonsai for over 2 years. He currently resides in the UK and works in sales.

Fehed Nicass

Fehed Nicass has been passionate about all things bonsai and botany focused for the past 3 years. What started out as a hobby has developed as a passion and he is now on a mission to teach and learn.

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