Bonsai Advice Requested - Ask Extension
I’m seeking some plant advice from a master gardener.
A friend of mine purchased a Chinese elm bonsai tree in early December of this year. She a...
Knowledgebase
Bonsai Advice Requested #923307
Asked January 04, 2026, 8:46 PM EST
I’m seeking some plant advice from a master gardener.
A friend of mine purchased a Chinese elm bonsai tree in early December of this year. She asked me to plant sit it. When it arrived it was green and lush. I kept it inside for about 5 days because I was worried about the cold, but after talking with a friend who is a horticulture therapist I put it back outside at her recommendation.
I don’t have a garage or cold basement so I tucked it between my sliding door and deck box to try and protect it from the wind and snow (but still allow some sun). During that time it got pretty cold (into the teens and 20s) and the tree started dropping its leaves (which my friend said was normal for an elm in the winter). I had been checking on it every few days, keeping the soil moist as needed.
I’m concerned that I may have shocked it with the cold. Is there any way to know if it’s ok or if I owe my friend a new tree? I’ve attached a few photos for reference from just after Christmas.
If it’s still ok, what advice can I provide my friend to tend to it over the winter and into the spring?
I appreciate any guidance you can offer!
Harford County Maryland
Expert Response
It would be unusual for a Chinese Elm (a cold-hardy plant in our area) to have green foliage as late as December. Perhaps your friend bought the plant from a nursery that had it indoors instead of outdoors? (Was it bought locally, or shipped from a warmer state?)
Typically, hardy plants need a cold dormancy period to continue to grow normally each year, so keeping them inside for too long (especially if they have already begun to go dormant, or are dormant) can interfere with their health. Ideally, the seller it was purchased from (if local) should have allowed the plant to be acclimated to cooling outdoor temperatures and waning daylight to trigger dormancy for the winter rather than keeping it sheltered. If it wasn't accustomed to cold or near-freezing temperatures, it would have needed to stay inside to avoid damage to the sapwood under the bark, which makes it difficult mid-winter to acclimate it to chilly weather in order to spend the rest of the season outside. (Hardy plants growing outdoors start the hardening-off process in preparation for winter many weeks or months prior to the onset of freezing weather.)
While the leaf damage may not be serious over the long term (the pictured leaves are dead, but to be fair, they would have died off naturally and been shed had the tree gone dormant normally), we can't tell if any buds for next year's growth, which trees usually produce before going dormant, are undamaged. A bigger concern, though, may be the roots: plant roots are not as cold-hardy as the above-ground parts of the plant, because in nature they don't need to be, since soil is insulating. In a container, roots are much more vulnerable to damage or dieback during winter due to temperature fluctuations and more rapid drying than soil in the ground would experience. Overwintering hardy plants in containers is always a challenge compared to planted in-ground specimens, though protecting the container from the brunt of the cold can help, and potted outdoor plants should be regularly checked for water. (Bonsai pots especially, since the soil used for growing them is normally much less moisture-retentive than typical potting soil.) Container protection for winter can involve burying the pot (more practical with containers larger than this one), surrounding the pot with a pile of any material that adds mass around the roots (wood chips, bark mulch, soil, etc....basically mimicking it being planted), or (when available) putting the plant in a location that gets cold but not much below freezing (garage, shed, etc.).
For now, you'd just need to wait until spring to determine if the tree will leaf-out normally and resume growth; it will be hard to tell in the interim how much (if any) dieback occurred. The dead leaves will fall off on their own, which is fine, and as you noted, just keep monitoring the container for root moisture and water as needed. Since it's already been exposed to cold, consider keeping it chilled until spring so it's accustomed to ambient temperatures and leafs-out "on time" in spring (leafing-out too early in response to a warm spell may result in late frost damage).
Miri
Typically, hardy plants need a cold dormancy period to continue to grow normally each year, so keeping them inside for too long (especially if they have already begun to go dormant, or are dormant) can interfere with their health. Ideally, the seller it was purchased from (if local) should have allowed the plant to be acclimated to cooling outdoor temperatures and waning daylight to trigger dormancy for the winter rather than keeping it sheltered. If it wasn't accustomed to cold or near-freezing temperatures, it would have needed to stay inside to avoid damage to the sapwood under the bark, which makes it difficult mid-winter to acclimate it to chilly weather in order to spend the rest of the season outside. (Hardy plants growing outdoors start the hardening-off process in preparation for winter many weeks or months prior to the onset of freezing weather.)
While the leaf damage may not be serious over the long term (the pictured leaves are dead, but to be fair, they would have died off naturally and been shed had the tree gone dormant normally), we can't tell if any buds for next year's growth, which trees usually produce before going dormant, are undamaged. A bigger concern, though, may be the roots: plant roots are not as cold-hardy as the above-ground parts of the plant, because in nature they don't need to be, since soil is insulating. In a container, roots are much more vulnerable to damage or dieback during winter due to temperature fluctuations and more rapid drying than soil in the ground would experience. Overwintering hardy plants in containers is always a challenge compared to planted in-ground specimens, though protecting the container from the brunt of the cold can help, and potted outdoor plants should be regularly checked for water. (Bonsai pots especially, since the soil used for growing them is normally much less moisture-retentive than typical potting soil.) Container protection for winter can involve burying the pot (more practical with containers larger than this one), surrounding the pot with a pile of any material that adds mass around the roots (wood chips, bark mulch, soil, etc....basically mimicking it being planted), or (when available) putting the plant in a location that gets cold but not much below freezing (garage, shed, etc.).
For now, you'd just need to wait until spring to determine if the tree will leaf-out normally and resume growth; it will be hard to tell in the interim how much (if any) dieback occurred. The dead leaves will fall off on their own, which is fine, and as you noted, just keep monitoring the container for root moisture and water as needed. Since it's already been exposed to cold, consider keeping it chilled until spring so it's accustomed to ambient temperatures and leafs-out "on time" in spring (leafing-out too early in response to a warm spell may result in late frost damage).
Miri
