How Cold Can a Juniper Bonsai Get?

A juniper bonsai can handle cold temperatures down to 15 degrees Fahrenheit. It has a very shallow root structure which should be protected from freezing with mulch or coverings. You can overwinter your bonsai outside with protection, or keep it in a garage or shed that will stay above 15 degrees.

Juniper tree varieties are the most popular types of trees for bonsai, especially for beginners, because they are very hardy trees. They make lovely traditional bonsai shapes but thrive even with a small level of neglect making them perfect for beginners.

They should be raised outside, which makes them vulnerable to extreme temperature fluctuations. Thankfully, these juniper bonsai are very durable trees.

There is more to overwintering a bonsai than just protecting it from freezing. During the winter, the bonsai tree should be in dormancy. It needs this period of rest to thrive during the growing season.

Depriving it of dormancy will kill the tree. Read on for more detail on how to protect your juniper bonsai from cold-weather damage while still protecting its seasonal life cycle so that it will mature and live for many decades.

Juniper Bonsai Cold Weather Dormancy

Juniper Bonsai Cold Weather Dormancy

It is important to know that your juniper bonsai will need to go dormant in the winter. You may think that it is dying, but it is not. It is preparing its soft tissues to overwinter in the cold weather.

However, junipers are not adapted to freezing temperatures. If you are growing your bonsai in a climate where temperatures dip below 10 degrees Fahrenheit, you need to take action to protect it from freezing.

First, consider the steps you need to care for your bonsai during the winter dormancy period.

  • Your bonsai tree does not need light during the winter because it is in a dormant state. Light is needed during the growth period so that the plant can make chlorophyll for growth energy. If you keep your bonsai in a warm sunny location all winter, you will deprive it of dormancy and the rejuvenation that it provides.
  • Your bonsai tree does not need as much water during the winter. This is because it is not in the growth phase. Check the pot weekly or biweekly and add just enough water to keep it from being dry. The tree is not taking up much water during dormancy, but it can not survive if it stays completely dry.
  • The tree draws sap away from leaves during dormancy, so the upper branches of the tree are prepared for lower temperatures. However, in nature, the root ball would be buried and insulated by a very deep layer of dirt. Since your bonsai is in a shallow pot, a freeze will kill the roots. This is the part you must protect.
  • If you allow your bonsai to get too much warmth and sunlight before the natural end of dormancy then you will bring it awake too soon. This is not all bad, but it will lose new growth if it gets caught in a late-season freeze.

Many new juniper bonsai owners get scared about killing their bonsai tree over the winter, but winter care is not as difficult as you might think.

You simply need to make a plan to protect the tree and then keep an eye on the weather. Alternatively, you can set the tree up in a safe spot for overwintering and leave it for the season.

Choose an Overwintering Location 

Choose an Overwintering Location

Since your bonsai is going dormant over the winter, its needs are much less than they are during the spring, summer, and fall growing seasons. It does not need light, it needs very little water, and it will not need pruning.

All it needs is protection from temperatures that are too cold. Here are some ways that you can protect your juniper bonsai from winter damage.

  • Timing of dormancy. At the end of fall, when the days are shortening rapidly and the outdoor trees are going dormant, it is time to select a place for your bonsai to rest during the winter. 
  • Outdoor overwintering. If you live in a climate that may see colder temperatures but not deep freezing, you can choose to bury your bonsai with or without the pot in the soil. Bury it in dirt and mulch all the way up to the first branches. Choose a location that will stay shady during bright days. 
  • Indoor overwintering. Place your bonsai in a garage, attic, or shed where the temperature will be cold but not dip below 10 to 15 degrees Fahrenheit. You do not need to worry about the tree getting enough light. In fact, less light is better to keep it in the dormant state.
  • Monitor the temperature. Whether you are overwintering indoors or out, there still may be times when the temperature dips dangerously low or strong driving winds and ice threaten to break the tree. Be ready to protect your tree with a sturdy box and blankets or a styrofoam cover.

Inside the garage the temperature can still dip below freezing, so be ready to cover the plant, especially the root ball with a blanket or styrofoam cover to keep additional heat on the plant and avoid freezing.

Remove the additional coverings as soon as the temperature warms up so that the tree can get fresh air and natural winter light but not bright warming sunlight.

The tree needs about three months of dormancy. This means that you can begin preparing it for spring awakening toward the end of the winter months by giving it more sunlight and water as needed.

The new growth will be thirsty. Be diligent to check temperatures nightly and cover your bonsai when the temperatures drop too low.

Problems with Juniper Bonsai Dormancy

50-year-old Bonsai

Many bonsai owners are disappointed or surprised to discover that their beautiful specimen needs a rest during the winter.

If you have purchased your bonsai tree at a mall kiosk or a mass-market home improvement store, then you probably were not given full instructions on how to keep your bonsai alive and thriving.

There are just a few things to keep in mind when preparing your tree for dormancy. 

  • If you are keeping your juniper tree indoors rather than outside, it must be able to go dormant. Place it in a cool location such as an attic or garage beginning in the fall so that it receives little light and gets the cold temperatures that it needs to rest. Indoor bonsai will die without an annual dormancy period.
  • If you place your juniper tree outdoors in an area where it receives warming winter sun it may trigger the tree to wake up and begin the growth cycle too early. This makes the sap rise back up the tree and begin new growth while there is still a risk of freezing temperatures that will kill the soft tissue.
  • If you place your tree in a nice place to safely overwinter, check the water weekly or bi-weekly, depending on the size of the pot. Do not let the tree sit in completely dry soil. Sometimes bonsai owners forget to check on the tree because it is out of sight during the winter months.

Bonsai tree dormancy can come as a nice rest after giving the tree constant care for three seasons of the year because the tree’s needs diminish greatly during this time. 


Bonsai tree growing is a peaceful and rewarding activity that requires such attentiveness and care for the beautiful trees. Juniper bonsai in particular are very hardy trees that can withstand more dryness and neglect than other varieties. However, it must be allowed to rest during the winter so it can burst out with new growth in the spring.

Juniper bonsai need to be prepared for overwintering and protected when the temperatures drop below 15 degrees Fahrenheit.

They must also be protected from winter sun and wind and not allowed to dry out. The tree will reward you with a flush of new growth and bright green beauty for you next year and for many decades to come. Looking to grow a bonsai tree yourself, have a look at this article about bonsai trees that are easy to take care of.

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