Keeping Your Bonsai Healthy in Winter

Bonsai care is especially important over the winter months. Just like their big tree counterparts, bonsai trees naturally start preparing for winter by losing their leaves. However, because bonsai trees aren’t rooted to the ground, they’re especially vulnerable to extreme winter temperatures and you need to take precautions to protect them. In this post, we’ll cover everything you need to know in order to keep your bonsai healthy this winter.

Preparing Your Bonsai for Winter

There is no universal formula when it comes to bonsai tree care. Different growers have different preferences when it comes to overwintering their bonsai. Some people take them inside, while others keep them in the garden all year around.

Generally, most trees from temperate parts of the world can withstand winter weather unprotected until the temperature drops down to -10°. Once it gets colder than this, you need to take measurements to protect your bonsai trees. There are a number of species that are an exception, including Azaleas, Trident Maples and Loropetalums.

For tropical trees such as the Ficus Ginseng care during winter includes taking them inside before temperatures start to drop, because even a light frost can damage their delicate leaves.

Fertilising Your Bonsai

Nutrients are a significant part of bonsai care during winter. Proper winter preparation should start during autumn. During the growing season trees produce sugars and carbohydrates which help they use during winter to stop themselves from freezing. Therefore, it’s very important to give your bonsai trees enough plant food throughout autumn to help them get enough nutrients to be ready for the cold.

Storing Your Bonsai Trees

Where you store them overwinter is detrimental to keeping your bonsai healthy. The ideal solution for protecting your trees even from the worst of weather would be a greenhouse, however, an unheated outbuilding can be just as good for keeping deciduous trees. Because they lose their leaves over winter, deciduous bonsai don’t require light and can be stored in your shed or garage when the weather gets cold.

If you have any benches or tables in your garden a smart solution would be putting your trees under them and covering the top and sides with bubble wrap to keep them warm enough.

Another solution many bonsai growers use is to take the trees out of their pots and plant them directly in the garden. This will protect the trees’ roots from the extreme cold and when spring comes around you can simply pot them back into the same pots.

Watering in Winter

Watering is another essential part of bonsai care all year around. Even if they have no leaves, bonsai trees will still need a small amount of water in winter. If you live in a place where it snows, a great way to tend to your bonsai trees is to store them in an unheated garage or shed and place snow in their pots on top of the soil. As the snow melts the trees will receive water.

Otherwise, you want to lightly water the soil once it becomes dry to the touch. Since your bonsai aren’t actively growing during winter you don’t need to fertilize them until they enter their growing period in early spring. 

Winter Dehydration

One thing to keep in mind is that generally it’s not the cold that harms your bonsai and more damage is often done through dehydration. If the soil around the roots of your tree freezes, the roots will stop drawing in water. The top of the tree, however, continues to release water. This is the main reason prolonged spells of freezing weather can cause major damage to bonsai. This can be worsened if the freezing weather is combined with strong winds or winter sin which further dehydrates the trees. A lot of the potential harm can be prevented simply by keeping your bonsai trees in a sheltered position out of extensive wind or sun.

Protecting Your Bonsai from Wind

If you’re overwintering your bonsai trees outdoor, instead of in a shelter such as a garage or a shed, it’s a good idea to place your tree where it can get protection from strong winds. The best place to keep your bonsai would depend on your garden’s layout, but generally, you want to keep it near a wall or a fence in the opposite direction of where the wind is coming from. For example, the east side of a wall or a fence can provide shelter from cold westerly winds.

Repotting

Come spring, your bonsai will probably need repotting, which makes winter the perfect time to prepare for this. You can go online and shop for a new pot and bonsai soil, or tools to help you shape your bonsai. You can also view instructional videos, or read up on how to repot your bonsai tree to ensure you won’t damage its delicate roots. As soon as the weather starts warming up and spring growth begins, you’ll be ready to repot your tree!

No matter if you decide to take your bonsai trees in for winter or keep them outside, be prepared for temperature drops can really give you peace of mind during the winter nights.

If you want to read up more tips on bonsai care all year round, you should check out our bonsai care calendar, where we have guides to help bonsai enthusiasts from all levels of experience. 

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