I have a quick question about overwintering, since we will be preparing for the colder months before we know it. A few trees I picked up over the summer (atlas cedar, hinoki cypress, nana) are supposed to be hardy during the winter months and survive colder temps for short periods of time (but I am not sure what that means - overnight, days, weeks). Right now, these trees live in our backyard in full sun (and we don’t have a cold frame or greenhouse). Will they be alright when temps start to drop into the 20’s overnight? We live in Colorado (Zone 5b), so our winters are mild compared to other regions (often getting into the high 30’s to 50’s during most winter days). Will these trees need extra protection? I plan to move our maples into our window wells. For conifers, I just worry that they’ll still need some sun (and the window wells can be dark). Any thoughts would be helpful.

You can keep the pines and junipers outdoors.
The maples can be outdoors also, perhaps in a unheated garage? To avoid the winds?
All of the deciduous that go dormant can be in this same unheated garage also.
Only tropical evergreens and deciduous should be inside.

What part of Colorado are you? My brother lives in Colorado Springs and I would not call his winters moderate. A barely heated out building might do ok there, but I would not leave my trees outside. I would aim at temps no lower than 20F.

Ivan Mann wrote: What part of Colorado are you? My brother lives in Colorado Springs and I would not call his winters moderate. A barely heated out building might do ok there, but I would not leave my trees outside. I would aim at temps no lower than 20F.

You are right, if temps get too low all trees will be in danger.
I guess around 25F to40F they will do OK outdoors.

Clicio wrote:

Ivan Mann wrote: What part of Colorado are you? My brother lives in Colorado Springs and I would not call his winters moderate. A barely heated out building might do ok there, but I would not leave my trees outside. I would aim at temps no lower than 20F.

You are right, if temps get too low all trees will be in danger.
I guess around 25F to40F they will do OK outdoors.

Colorado Springs is way below that December to February. We laugh sometimes I am running the air conditioner when he is running the snow blower.

The best bonsai answer, IMHO, is to find a group or person near you and find what they do in that climate and when they do it. Every area is different and advice from one area might not match your area very well.

Key is to know what you get winterwise.

I protect olives, pomegranate and similar when it starts to get frostier. Pretty much all others just have to deal with the weather. The species you mention seem fine with temps to -10c. My junipers and hardy broadleaves also get to deal with colder, no concerns there.

leatherback wrote: Key is to know what you get winterwise.

I protect olives, pomegranate and similar when it starts to get frostier. Pretty much all others just have to deal with the weather. The species you mention seem fine with temps to -10c. My junipers and hardy broadleaves also get to deal with colder, no concerns there.

Average low in January in Colorado Springs is 15F, about 8C. However they go for weeks at a time around 0F, which is about -17 C. I remember these numbers because my brother tried to convince my wife that living in an area with three to five feet of snow on the ground for months was no problem and we should move there. Those temps would require some protection. You have to look at your area.

I have.a problem with squirrels in the back yard knocking the bonsais over. He has deer roaming the back yard. We all have our problems.

Ivan Mann wrote:

leatherback wrote: I have.a problem with squirrels in the back yard knocking the bonsais over. He has deer roaming the back yard. We all have our problems.

I have birds.

Thanks for the insights here. We live in Denver, which is fairly similar to Colorado Spring. It can get below 10 to 15 F at night for weeks at a time, but often the cold and snow doesn’t sick around. Usually evening temps drop into the high 20’s, however. Would a frost cover help? I could just move everything into the garage at night, if that makes the most sense.

Main concern would be drying out of the plants for me. Unless covered in snow I would want the rootball to defrost every once in a while, say ever 1-2 weeks.

Have you seen this?
www.growingbonsai.net/what-kills-bonsai-in-winter/