How to Protect Bonsai in the Winter

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Are you looking for ways to protect your bonsai trees from winter damage? There are several things you can do to ensure they survive the cold months.

Bonsai trees are beautiful plants that require special care during the colder seasons. They thrive in warm temperatures and should never be exposed to freezing temperatures. If you live in a temperate climate where winters are harsh, you’ll want to take precautions to prevent damage to your bonsai tree.

It’s essential to learn how to overwinter your bonsai tree to protect it from the cold elements.

This article will include the best types of Bonsai trees for winter months and tips to help you protect your bonsai tree from the cold weather. 

Can Bonsai Survive Winter?

Bonsai trees can absolutely survive the winter, but every bonsai gardener needs to know what to do to protect their bonsai tree. Winter normally signifies a period of rest for Bonsai trees and storing your bonsai correctly will protect your bonsai, and all the time and effort you have spent cultivating it.

Best Types of Bonsai Trees for Winter

Which Bonsai trees are best for winter? Let’s begin with bonsai types. Each bonsai type will have a cold hardiness capability according to the USDA.

The four bonsai types are:

  • Tropical
  • Semi-tropical
  • Temperate
  • Hard

The tropical bonsai needs to be protected in winter, particularly from temperatures that reach freezing levels. Tropical trees make wonderful indoor bonsai plants, particularly during the winter season.

A semi-tropical bonsai will survive frost and colder temperatures that are moderate, but only for a short time.

A temperate bonsai will tolerate freezing temperatures because freezing temperatures will not damage the tree’s root system.

A hard bonsai tree withstands cold and freezing temperatures without being damaged.

Indoor Bonsai Trees in the Winter

Indoor Bonsai trees will not face major issues during winter because they rarely reach freezing temperatures indoors.

Remember to provide adequate sunlight since the winter days are shorter in the winter. Grow lights can be used to help provide enough light. 

Keep your bonsais away from heating and cold drafts to avoid temperature changes. Exposure to door and window drafts can cause drastic changes in temperatures.

Outdoor Tropical and Subtropical Bonsai Trees

Tropical bonsai species expect a warmer climate, so they risk dying in cold temperatures. Both tropical and subtropical species need to be moved indoors if you live in a climate with freezing temperatures, snow, hail, and ice. 

Building a greenhouse with temperatures above freezing is an alternative to keeping bonsai trees and other plants inside your home. 

Outdoor Hardy Bonsai Species

If you have a bonsai species that grows naturally in colder climates, you will not need to do a lot. This is true especially for deciduous trees that naturally lose their foliage and then enter dormancy in the winter.

These Bonsai trees need their period of dormancy for their overall health. If you move these trees indoors, they lose their necessary period of rest.

Best Bonsai Species for Winter

Some bonsai tree species resist extreme weather and temperatures with little or no difficulty. Some can survive temperatures as low as 45° Celsius.

Most of these tree species should be cultivated outdoors because they appreciate colder conditions.

  • Birch
  • Cedar
  • Cypress
  • Elm – e.g. Chinese Elm
  • Larch
  • Maple – e.g. Trident Maple, Japanese Maple
  • Pines
  • Spruces
Bonsai Tree

How to Protect Your Bonsai Tree in the Winter

Learn how to take care of your Bonsai tree throughout the year, so it will survive in the winter. 

Preparations Before the Winter

If you have an outdoor or indoor/outdoor bonsai tree, from approximately March through November, when the weather is dry and warm, position your bonsai outdoors for sun exposure.

Sunlight is necessary for tree growth before dormancy. Feed your bonsai with a good bonsai fertilizer through August. Two months before winter arrives, stop pruning, so the tree doesn’t suffer from weakness when winter arrives.

The Beginning of Temperatures Dropping

Your bonsai can safely experience the first drop in temperatures of the year. This will contribute to triggering the bonsai’s cold hardiness. It is important temperatures do not drop lower than 35°F to keep it from freezing..

During Bonsai Winter Dormancy

During your Bonsai’s dormancy period, an outdoor bonsai species can be moved to a dark, cool, unheated indoor space such as a garage. If you possess a hardy species, it can remain outdoors with adequate protection.

If you have an indoor bonsai, during dormancy it can remain in a dark location as long as the temperature where it is located remains between 20° and 50° Fahrenheit.

If your bonsai normally sits in a shallow container, make sure the roots are covered by soil or consider repotting it into a larger bonsai pot.

Should you decide not to leave your bonsai outside, you can refrigerate it so that it fully enjoys a dormancy resting period. This can be a garage, attic, basement, or similar as long as the temperature measures between 35° to 40° F.

If you opt for indoor dormancy storage, toward the end of winter, move it to a normally heated indoor environment in preparation for the arrival of spring. This will allow for a gradual adjustment in advance of the new growing season and warmer temperatures.

After Winter Dormancy 

When the cold temperatures subside and there is no longer a risk of root damage, you can transfer your bonsai from your garden bed back to its container or return it to its normal-sized container.

Pruning can begin again for structural maintenance.

Ten Tips for Bonsai Winter Protection

Here are the top tips to protect your Bonsai trees in the winter. 

1. Know Your Bonsai and Climate

Know your bonsai species, so you know if your bonsai needs to be brought indoors or not. Know your local climate and how cold it gets to be able to prepare for the winter.

A tropical bonsai requires warm temperatures, so it should be moved indoors or to a greenhouse where the environment will be warmer and temperatures constant.

2. Give it Enough Light

If your bonsai is a tropical or semi-tropical species and you decide to cultivate it indoors during the winter months, your bonsai should be positioned in a window or on a windowsill during the day for light. This will guarantee that it receives sufficient light for its health.

You can use indoor grow lights if days are dark or shorter, but take care to not overexpose your tree to ultraviolet rays from those lights. That’s similar to giving your bonsai too much direct sunlight.

Bonsai Tree by Window

3. Avoid Extreme Temperature Changes

Remember that bonsais cultivated indoors should not be placed near heating vents that can scorch the tree. They do not appreciate extreme temperature changes in their environment, so vents that turn on and off may produce frequent temperature jumps.

Place your bonsai in a location where temperatures remain relatively stable.

4. Check For Pests

Take advantage of the dormancy period to check your bonsai thoroughly for pest infestations and apply any necessary treatments.

5. Extra Bonsai Root Care

Once bonsai leaves drop, any sugar (sap) that a bonsai tree has stored will be directed to the root system, so particular care of the roots becomes crucial with adequate protection. Outdoor trees will need some form of root protection to avoid freezing or cold temperature damage.

6. Wrap Your Bonsai Tree

Wrapping Bonsai tree trunks will help protect them from the cold weather and strong winds when outdoors. 

For outdoor bonsai trees, the first thing to do at the beginning of colder winter weather is to wrap your bonsai tree in a clean cloth or a newspaper. Then wrap the tree in plastic over the cloth or newspaper wrap.

Do not wrap your bonsai directly in plastic as plastic will act as a conductor to the outside temperature, so there’s no protection from the cold.

Another option is placing your bonsai in a Styrofoam box or beverage cooler box. Remove the lid and place your bonsai inside. This will insulate your bonsai and protect it from winter winds.

Hardwood boxes that are 6 to 12 inches are also an option. Surrounding your bonsai with haybales works as well if you are not subject to extreme temperatures in your area.

Once you have selected a box, it should be a bit higher than the highest branch for optimal protection. Position your bonsai inside, fill the box with mulch, leaves, and bark and cover the pot of your tree. Make sure your box protects the bonsai from wind, and that the soil is permeable for proper drainage.

A top layer of mulch can help stop ice from forming on the soil and freezing the root system.

7. Don’t Forget to Water

If your bonsai remains outdoors for the winter, do not forget to water the plant. While your tree will not require much water during its dormancy period, it will still require some.

Water your bonsai tree when the soil bed dries out and not when still moist.

8. Put Your Bonsai Under a Bench

One solution for leaving your bonsai outdoors during the winter is to position your tree under a garden bench.

Then cover the sides of the bench with bubble wrap or plastic to protect your tree from the cold, snow, and hail. 

If the bench seat is not solid, cover the seat’s holes in plastic, so rainwater and snow don’t get through. 

9. Transplant the Bonsai to a Garden Bed

Another option is to transplant your outdoor bonsai directly into your garden bed, removing it from its container. In this manner, the root system will have maximum protection with extra garden soil covering it from the cold versus keeping it in a bonsai pot. 

10. Transplant the Bonsai to a Larger Container

Should you not have an outdoor garden or not have any space for a transplant, you can move your bonsai to a larger container with garden soil.

The tree roots should be placed two to three inches deep from the soil top to guarantee adequate protection for the bonsai’s root system.

Bonsai Trees in the Winter Final Thoughts

To protect your bonsai tree in winter, it is important to have all the necessary information about your bonsai tree species and the climate where you live if you are cultivating an outdoor bonsai tree. Thanks to the versatility of bonsais, they can be cultivated both indoors and outdoors. 

Even if you cultivate a hard tree species, it will still require proper care and maintenance. It’s important to stay consistent for to keep your bonsai tree safe. 

For more on bonsais, check out these articles: 

Fast Growing Trees and Plants

Bonsai Boy Plants and Pots

Photo of author

Written by:

Amy Walsh
Amy Walsh is a passionate indoor gardener, deeply engrossed in the world of houseplants and herbs. Her apartment is a lush sanctuary of foliage, reflecting her journey from hobbyist to devoted botanist. She's constantly exploring the latest in smart garden technology, eager to share her insights on nurturing green spaces indoors. Alongside her botanical pursuits, Amy enjoys connecting with nature and friends, continually enriching her lifestyle with greenery and growth.

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