Winter care of Japanese maple bonsai depends on factors such as age of the tree, variety of the Japanese maple, growth stage the tree is in (dormant or in early leaf out) and whether the tree is planted in a pot or in the ground.
Japanese maple bonsai trees are tough trees and can handle winter season easily. When planted in the ground, the trees are hardy to zone 5-9. However, when planted in bonsai pots, they are hardy to zone 6-9.
What to do with Japanese maple bonsai in winter?
Keep the Japanese bonsai tree outdoors in winter. It is also fine to leave it outdoors if it rains at that time. This can also provide the bonsai with some natural water. In addition, you can apply some mulch to the bonsai soil.
If the temperatures drop below freezing, bring the bonsai tree indoors in an unheated garage or shed. Make sure that you bring the bonsai tree outdoors again as soon as the temperatures return to normal. If you keep the bonsai indoors for too long then the tree can leaf out early.
Protect Japanese maple bonsai from frost
The layer of ice on the tree during frost can cause tip damage. In young trees, this tip damage can spread throughout the plant. It can even kill some varieties of Japanese maple bonsai.
Mature Japanese maple trees are very hardy and tolerates frost very easily. They easily recover from frost, provided they are watered thoroughly after frost. Young trees, on the other hand, are more susceptible to frost. In particular, young trees will be severely damaged by late freezes or frosts.
Whatever the case may be (mature or young), providing the right frost protection for your Japanese maple bonsai tree is always advisable. This is to ensure that the tree remains healthy and the tender foliage is protected.
- Make sure to follow the weather forecast. It is always wise to be prepared and know when your area will have frost.
- If the tree is potted in a pot, you can bring it indoors to an unheated shed or garage. You can bring it back to its outdoor location when the frost is over.
If you have a large collection of bonsai trees, it is likely that you won’t be able to bring all the bonsai trees indoors. Also, if your tree is planted in the ground, it is not possible to bring it to a protected shelter. In that situation, covering the bonsai tree, providing light shade, avoiding water sprays, keeping the bonsai tree in a windy location or application of Anti-desiccants / anti-transpirants can be helpful.
Cover the bonsai tree
Covering your bonsai tree before the onset of the frost can be very helpful in protecting your bonsai from the frost. Cover the tree the night before frost is expected. Heavy wind will help in removing the frost. Hence, the time of the day when frost has the most potential to damage the tree is just before sunrise when the wind is not present. Making sure that the trees are covered at this time is essential.
Which tree to cover?
Covering the bonsai tree also depends on the growth stage your bonsai is at. For example, trees that are dormant or have leaf buds that are just beginning to appear do not need to be covered. On the other hand, trees that leaf early and are in full leaf and trees that are in between the dormant and full leaf stage will need covers for frost protection.
What to use as a cover?
Make sure that you are using the right material to cover the bonsai tree. Use a frost cover (you can buy it from nurseries) or you can even use a light bed sheet. Frost covers are white, thin, light and permeable covers that are specifically designed for this purpose.
Use a light colored bed sheet as a dark colored bed sheet might hold more heat and damage the bonsai. One key thing to note is that before frost, high wind usually occurs. Hence, secure the covers so that they are not blown away by the wind. Also, use a light weight cover. As heavy covers can damage the plant.
You should not cover your tree with a plastic bag. Plastic retains more heat and dehydrates the plant even more. Frost will dehydrate the plant and using a plastic bag on top of that will amplify the dehydration process.
Additionally, some bonsai growers use a bucket (or similar container) to cover the tree and keep a lamp as an artificial heat source for the tree. This is not recommended as it will burn the bonsai tree in just a few hours.
Use Anti-desiccants / Anti-transpirants
These surface sprays help prevent foliage from becoming too dry during the winter. This will especially protect the new growth.
Provide shade to the bonsai tree
Providing the tree with some shade in the later part of the day can result in delaying the leaf out of the tree (by almost 2 weeks). As the leaf out is delayed, you will be able to protect the tree from frost.
Select a suitable outdoor location for the bonsai tree
Wind is good at the time of frost. Wind will break the frost. Bonsai trees that are kept in locations that has very low to no wind will need frost protection. Hence, keeping the tree in a location with ample wind can help you in protecting the bonsai tree from frost.
Use Japanese maple varieties that leaf out late
You can also choose Japanese maple varieties that leaf out later. This will completely eliminate the need for frost protection in early spring.
Don’t spray water on the tree
Make sure the tree is not sprayed by water. For example water sprays from sprayer systems or sprinkler systems. This will increase the formation of ice on the foliage. Japanese maples have very tender foliage and they will easily get frost damage.
How to recover Japanese maple bonsai from frost?
Frost damage does not show up as soon as the frost is over. It might take a day or two for you to see the frost damage and wilted leaves.
When the frost is over, make sure the plant is thoroughly watered. Watering will greatly aid the plant’s recovery. Let the soil dry out a little before you water the plants again. Do not over-water the tree.
In addition to watering, another thing you can do is apply liquid fertilizer. This can give your plant a slight boost in recovering the new buds that got damaged. Liquid fertilizer is preferred because of its fast action.
The time taken to recover depends on the age of the tree and the variety of the tree. Fertilize every 2 weeks. You should see new buds emerging from the tree soon.
Protect Japanese maple bonsai from Cold snap
Cold snap is a little different from frost. Cold snap is basically a sudden drop in temperature after a long period of warm weather. Also, cold snaps are generally colder than frost. Avoid exposing your Japanese maple bonsai to extreme temperature variations.
Trying to stay ahead of cold snaps by keeping track of the weather forecast is always advisable.
If you bonsai is dormant you do not have to worry about much protection. It will be able to handle this temperature change. Bringing a dormant tree indoors will trigger its activation by creating “false-spring“.
On the other hand, if your bonsai is active or starting to become active (buds are about to open), bring the bonsai tree indoors in an unheated garage or shed.
It is also very important to bring the bonsai trees back outdoors as soon as the cold snap is over. Don’t keep them indoors for too long (i.e. a week or 2) or else they will leaf out. Keep in mind that potted plants are more active than those on the ground. They leaf out quicker.
For active/slightly active plants that can not be brought indoors or plants that are grown on the ground, cover the plants with frost cover or bed sheet to protect the tree from cold snap or late frost.
Do not cover with plastic. Plastic bags will retain more heat. The plant will not be able to absorb water from the soil fast enough to compensate for the excess heat inside. Furthermore, the plastic bag will act as a microwave for the plant. The bonsai will eventually dry out.
Additionally, to make your Japanese maple bonsai more resilient to such conditions, avoid over fertilization. Grow your bonsai at a moderate rate. Fertilize moderately with nitrogen (and no nitrogen in the fall – or else the tree will have trouble entering dormancy in winter). This will prevent the tree from having elongated cell walls and it will be able to sustain these low temperatures relatively easily.
Furthermore, avoid fertilizing your Japanese maple in the early spring. You do not want your tree to be very active during those early cold snaps.
After the cold snap is over, make sure your bonsai tree is thoroughly watered. This will help the tree recover more quickly.
