How to Protect Bonsai in Winter

The unique appearance of Bonsai trees sets them apart from other household plants, meaning they are prized by garden enthusiasts all over the world.

However, due to their small size, they are much more vulnerable to cold weather than normal trees and need extra care during the colder months of the year. Before committing to owning a Bonsai plant, it is best to develop an understanding of their specific needs.

Although these solutions tend to be fairly inexpensive and simple to put into practice, you should take into account all factors that may affect your Bonsai plant.

Whether you are an experienced gardener or new to plant care, it is easy to reach a solution that works for you. Read on to learn the basics of how to protect your bonsai during the winter. 

Overwintering a Bonsai: Warm vs. Cold Climate

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One of the most important factors in protecting your plant is the climate where you live. Temperature is the most important factor, as extreme highs and lows can be hazardous to the Bonsai’s health.

Before committing to a method for protecting your tree, first determine the type of climate you live in. This is especially important to consider in the case of a tropical Bonsai.

Before the arrival of winter, you will need to take steps to prepare your Bonsai for its dormant period. In order to ready the tree for this part of its life cycle, it is advisable to cease the use of nitrogen fertilizer.

Depending on where you live, this will normally take place in the fall. It is also advisable to remove any weeds that you may find in the pot, and prune the plant before winter weather arrives. 

If you live in an area where you expect to experience temperatures lower than 15 degrees Fahrenheit, it is advisable to overwinter your Bonsai in a more protected environment.

This is especially true for Bonsai, that originate in warmer climates. Options for those who live in colder regions include:

  • Green house
  • Cold frame
  • Other indoor enclosure

If you live in a region that does not regularly experience these low temperatures, then these measures may not be necessary.

However, it is still important to protect the Bonsai from winds that may damage them. If you do not live in a region that experiences these temperatures, you may wish to insulate the plant with sheets or styrofoam blocks.

Protect Bonsai from Temperature Fluctuations

Just like most normal sized trees, Bonsai enter a state known as “dormancy” during the cold winter months. Like animals that hibernate by sleeping through the winter, the plant’s dormant state helps it to survive low temperature and conserve energy.

This means that the plant does not only need to be protected from low temperatures, but also needs to be prevented from warmer ones, as this may interrupt its dormancy.

If warm temperatures interrupt the tree’s dormancy, it may begin to bud, and in this state it will be particularly vulnerable to the cold. The outcome of this is likely to be damage to the tree. 

For this reason, it is best not to dramatically change its environment once you have prepared the plant to weather the cold. Late frosts can also be hazardous to trees emerging from dormancy, so it is important to protect against these as well.

As a general rule of thumb, do not place your bonsai in environments where there are radical changes in temperature throughout the day. 

Avoid Overwatering Bonsai During the Winter

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Everyone knows that watering is an important part of taking care of practically any plant, but likely they are not familiar with the specific requirements of the Bonsai.

Once the soil dries out and the tree enters its dormant state, it is best to water the plant minimally. It is in a state where it does not need to consume much liquid, and noting this will help it stay healthy all winter.

You should not allow the soil to completely dry out, but especially damp conditions are not required during the wintertime. Damp conditions may harm the dormant tree.

Overwatering is a common beginner’s mistake, but also an easily avoidable one. You should also note that a tree with frozen roots should not be watered, as this is actually quite hazardous to the organism, potentially permanently harming the tree.

Always Have a Lightsource 

Although they are not visibly growing leaves or blooms in their dormant state, a Bonsai still requires light to thrive during the winter.

It will not require as much light as during the warmer months, but this is nonetheless an important factor. You should be sure to provide the tree with a consistent light source. 

There are a number of options to consider, including placement in front of a south-facing window or additional greenhouse lighting.

As long as your bonsai is placed near some kind of light source, your bonsai should be able to photosynthesize and create the energy it needs. 

Adjust Humidity Levels 

Trees are usually accustomed to a certain level of humidity that allows them to thrive, and this holds true for Bonsai trees as well. Like their larger counterparts, Bonsai require a stable environment to remain healthy. Tropical Bonsai, in particular, require humidity for their health.

There are several methods you may choose to keep humidity stable. Many people opt for a humidifier, while others choose to mist regularly with a spray bottle.

While a spray bottle may be a more cost-effective option, a humidifier should provide more predictable conditions for the tree, contributing to its overall health. 

Alternatively, a dehumidifier might be necessary if you live in a tropical environment with too much humidity. Ultimately, it depends on how much humidity your bonsai is comfortable with and adjusting the environment you place your bonsai in to accommodate this need. 

Warning Signs to Look out for During the Winter

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Even if you provide a healthy environment for the Bonsai to overwinter, it is still necessary to keep an eye out for any sign of trouble, just as you would during the rest of the year.

A dormant tree is susceptible to many of the same issues as it would be any other time of the year. Warning signs may include:

  • Discoloration of leaves or needles
  • Signs of infestation
  • Irregular formation of leaves or needles

If you notice any of these symptoms, then you should reassess how you have been caring for your bonsai. There are many potential causes such as underwatering, overwatering, too little sunlight, or infertile soil that lacks the proper nutrients your bonsai needs.

With some careful thought, you should be able to pinpoint the cause of the problem and adjust your behavior accordingly to care for your bonsai. 

As previously discussed, the winter months pose specific challenges for your bonsai. If your bonsai thrives in humid conditions, then you will need to place a humidifier nearby to keep your bonsai healthy.

Winter is usually a dry season, so you may need to alter your bonsai’s environment to ensure it is living under optimal conditions. 

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Alternatively, if your bonsai is infested with pests, then you will need to find a way to remove them immediately. Many insects feed off of the leaves or other parts of bonsai trees, so you will need to protect your bonsai tree from these pests if you want it to stay healthy. 

One way to deal with pests is placing your bonsai in a greenhouse with some ladybugs. After a few weeks, the ladybugs will eat all the pests hurting your bonsai.

If you do not have a greenhouse, other common methods you can use are soil insecticides or picking off the pests by hand with some tweezers. These methods are inexpensive and require little equipment to perform properly. 

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