Winter Bonsai Care - Colorado

[Grizzly25]

Hi Everyone! I am fairly new to Bonsai, and have accumulated a few young trees since this spring. As fall and winter approach in Colorado, I want to make sure I take proper care of each tree. The information I have found online hasn't been the most helpful, so any advice would be appreciated! I do not have the ability to plant them in the ground during winter, and have thought about getting a cold frame but do not know a ton about it.

The trees I have that I am looking to care for are:

Jeans Dilly Alberta Spruce (~5in. tall)
Mikawa Yatsuba Japanese Maple (~9 in. tall)
Juniper (~3 in tall, ~7 inches long)
Fern Leaf Hinoki Cypress (~5 in tall)

 

[stubmle]

I've got a Jean's Dilly myself. Wouldn't worry about that one too much, Alberta gets pretty cold. As long as it's out of the wind and doesn't totally dry out it should be fine.

What is your situation like? You can't plant in the ground- how about placing them on the ground and mulching in? Or are you in an apartment with a balcony?

 

[bonsaichile]

I am in Denver. i keep my trees on the ground under my benches most of the winter, unless there is a cold spell and temps are lower than 25 F, in which case I put them in my unheated garage

 

[JesseKane]

With deciduous trees the biggest thing to looks out for in Colorado are the big temp swings in the late winter and spring. If your trees start to break dormancy early they will be more susceptible to the cold snaps we get. I put my trees in the shadiest spot I have on the north side of the house with a fence to block the drying winds. Find a place where the snow melts last and mulch them in there. Maple might be better off in an unheated garage, they can take a freeze but not much below 25F at the roots. Mine push buds in March to mater what, so be ready to move them in and out of protection in the early spring. Once buds appear the maple will be extremely sensitive to frost.

The spruce and hinoki are fine on the ground with mulch around the pots and protection from the wind. Juniper might be good as well depending on the species.

 

[Attmos]

Hi Everyone! I am fairly new to Bonsai, and have accumulated a few young trees since this spring. As fall and winter approach in Colorado, I want to make sure I take proper care of each tree. The information I have found online hasn't been the most helpful, so any advice would be appreciated! I do not have the ability to plant them in the ground during winter, and have thought about getting a cold frame but do not know a ton about it.

The trees I have that I am looking to care for are:

Jeans Dilly Alberta Spruce (~5in. tall)
Mikawa Yatsuba Japanese Maple (~9 in. tall)
Juniper (~3 in tall, ~7 inches long)
Fern Leaf Hinoki Cypress (~5 in tall)

I lived in CO for about twenty years and my siblings are still there.

I think being very specific about your location would help people give advice in this particular situation. The mountains aren't like the front range or the eastern plains, and most of the valleys have different weather patterns than each other and the mountains, they get different amounts of light and heat.... etc...

 

[Tieball]

I lived in CO for about twenty years and my siblings are still there.

I think being very specific about your location would help people give advice in this particular situation. The mountains aren't like the front range or the eastern plains, and most of the valleys have different weather patterns than each other and the mountains, they get different amounts of light and heat.... etc...

You know the land and impacts really well. A lot to consider.

 

[Attmos]

You know the land and impacts really well. A lot to consider.

I'm learning.

 

[Grizzly25]

I've got a Jean's Dilly myself. Wouldn't worry about that one too much, Alberta gets pretty cold. As long as it's out of the wind and doesn't totally dry out it should be fine.

What is your situation like? You can't plant in the ground- how about placing them on the ground and mulching in? Or are you in an apartment with a balcony?

Its a townhouse, but the back patio is concrete and gravel. It's fenced in though, so should be pretty protected from the wind. I have heard that putting it in the garage when it gets really cold can be beneficial as well

 

[Grizzly25]

I am in Denver. i keep my trees on the ground under my benches most of the winter, unless there is a cold spell and temps are lower than 25 F, in which case I put them in my unheated garage

Oh thank you! It's great to hear from someone in the area. Do you think mine will fare similarly even though they are pretty young?

 

[Grizzly25]

With deciduous trees the biggest thing to looks out for in Colorado are the big temp swings in the late winter and spring. If your trees start to break dormancy early they will be more susceptible to the cold snaps we get. I put my trees in the shadiest spot I have on the north side of the house with a fence to block the drying winds. Find a place where the snow melts last and mulch them in there. Maple might be better off in an unheated garage, they can take a freeze but not much below 25F at the roots. Mine push buds in March to mater what, so be ready to move them in and out of protection in the early spring. Once buds appear the maple will be extremely sensitive to frost.

The spruce and hinoki are fine on the ground with mulch around the pots and protection from the wind. Juniper might be good as well depending on the species.

Wow so much great information, thank you! Unfortunately, my outdoor area where I have them are on the south side and it's really my only option. I do have an unheated garage as well where I can store some though. I will definitely take your advice! Do you think the heartier species are more susceptible since they are so young? Or should they still do pretty well?

 

[Grizzly25]

I lived in CO for about twenty years and my siblings are still there.

I think being very specific about your location would help people give advice in this particular situation. The mountains aren't like the front range or the eastern plains, and most of the valleys have different weather patterns than each other and the mountains, they get different amounts of light and heat.... etc...

Very fair point, I am in the Denver area!

 

[Orion_metalhead]

For such a small number of trees, I would put them against a concrete wall that stays shaded, cover them with 4" of mulch, and provide a definite windbreak. check periodically that the pots stay slightly damp, but mulch usually will do a decent job of holding in moisture.

 

[JesseKane]

Wow so much great information, thank you! Unfortunately, my outdoor area where I have them are on the south side and it's really my only option. I do have an unheated garage as well where I can store some though. I will definitely take your advice! Do you think the heartier species are more susceptible since they are so young? Or should they still do pretty well?

Young trees are pretty resilient and can recover quickly as long as their roots are protected. Plus, if a few buds or the tip of a branch dies it's not so big of a deal compared to a mature bonsai in refinement. Your first couple winters will be a learning experience for what works for your situation, pay attention to the patterns around your property during storms and throughout the spring. As soon as you see buds start to swell then think about bringing your trees into the garage during a sudden cold snap, especially if it's one of our 65F high to 15F low sort of days.

 

[Attmos]

You know the land and impacts really well. A lot to consider.

Was I being overly detailed? As I said, I'm still learning... lol

 

[Tieball]

Was I being overly detailed? As I said, I'm still learning... lol

Not at all. I enjoyed reading your detail of the terrain climate changes….and all the growth that survives the conditions. Weather and the impacts fascinates me. Sometimes I seem to live in the bubble of my own surrounding environment. However, the western states are my favorites for interesting climate, mountain, ground and seasonal changes.

 

[bonsaichile]

Oh thank you! It's great to hear from someone in the area. Do you think mine will fare similarly even though they are pretty young?

Very likely. Some of mine are root cuts I started 3 years ago

 

[Leo in N E Illinois]

If your south facing back yard has no shady spot to set your trees, try using a styrofoam cooler. Punch a few holes to get a little air circulation, doesn't need to be many holes. Place trees in the cooler once deciduous trees are leafless, and night temps regularly dip below 28 F (-3 C) more than once or twice a week.

The often repeated adage that most hardy tree roots can not survive temperatures below +25F is nonsense. I live in the mid-west, here water mains are required to be buried 6 feet below grade, simply because the ground freezes that deep. The surface layer of the ground, where our landscape tree roots are, gets as cold as the average air temperature. This can be near 0 F or even colder in a cold January or February. (daytime highs, might be +5 F, night lows can be as low as -17 F ( -27 C)). No way does our surface soil stay above +25F when night time lows are -17 F. Tree roots are much more winter hardy than the Pacific Northwest dwelling authors of the article that asserts an absolute +25 F limit for temperature tolerance. Look at your USDA climate zone map. Trees hardy to climate zones one or more zones colder than your location should do fine in pots just set on the ground and mulched in, if in a shady spot, or set in a cooler if a sunny spot is your only option.

Warm sunny days in middle of January are when most freeze-thaw damage happens. The rapid return of cold is rough. Here the cooler helps prevent heating up on those midwinter thaws,, and slows the abrupt cooling when "normal" cold returns.

I set my pots of zone 5 and zone 4 hardy species on the ground, and mulch enough that they are protected from wind. I generally have had good survival rates, near 100%. Ceramic pottery is another issue, The quality of the clay and the shape of the pot play an important role in surviving freeze thaw cycling. Most trees in training are in plastic or mica pots. Trees in good ceramic regardless of hardiness get wintered in unheated well house to save the pottery rather than the tree.

 

[JesseKane]

If your south facing back yard has no shady spot to set your trees, try using a styrofoam cooler. Punch a few holes to get a little air circulation, doesn't need to be many holes. Place trees in the cooler once deciduous trees are leafless, and night temps regularly dip below 28 F (-3 C) more than once or twice a week.

The often repeated adage that most hardy tree roots can not survive temperatures below +25F is nonsense. I live in the mid-west, here water mains are required to be buried 6 feet below grade, simply because the ground freezes that deep. The surface layer of the ground, where our landscape tree roots are, gets as cold as the average air temperature. This can be near 0 F or even colder in a cold January or February. (daytime highs, might be +5 F, night lows can be as low as -17 F ( -27 C)). No way does our surface soil stay above +25F when night time lows are -17 F. Tree roots are much more winter hardy than the Pacific Northwest dwelling authors of the article that asserts an absolute +25 F limit for temperature tolerance. Look at your USDA climate zone map. Trees hardy to climate zones one or more zones colder than your location should do fine in pots just set on the ground and mulched in, if in a shady spot, or set in a cooler if a sunny spot is your only option.

Warm sunny days in middle of January are when most freeze-thaw damage happens. The rapid return of cold is rough. Here the cooler helps prevent heating up on those midwinter thaws,, and slows the abrupt cooling when "normal" cold returns.

I set my pots of zone 5 and zone 4 hardy species on the ground, and mulch enough that they are protected from wind. I generally have had good survival rates, near 100%. Ceramic pottery is another issue, The quality of the clay and the shape of the pot play an important role in surviving freeze thaw cycling. Most trees in training are in plastic or mica pots. Trees in good ceramic regardless of hardiness get wintered in unheated well house to save the pottery rather than the tree.

I'd be really curious to see actual measured ground temperatures during winter. I was surprised at the temperature in my pots last winter during our coldest storm and discovered it was due to the latent heat of the water in the soil. With air temps below 0F, the temperature a couple inches into a 6" nursery container stayed above 30F. Water has a very high heat capacity, I wouldn't be surprised if ground temperatures stay above 25F a few inches down even during extended periods of average air temps below 0F. Especially if you take into account the insulating effect of ground litter or grass.

Hmm I think I might run that test myself this winter! Here's my post from last winter if anyone is interested in nerding out about physics: https://www.bonsainut.com/threads/cool-physics-in-my-cold-frame.67420/

 

[Deep Sea Diver]

As the Pacific Northwest author of this resource, a cold weather guy who was born in Milwaukee (@Leo in N E Illinois ) and raised in Chicago…. it’s interesting to see my work being talked about. Also spent a winter in the Arctic Ice Pack, diving in the Arctic Ocean (and Antarctic previously)…. Taking data about Ice and also water temperatures just below the ice flows…amongst other items.

The fact is tree roots are not evolved to be exposed to low temperature. The roots are the most vulnerable part of a tree.

Think about tree roots and frozen ground. Once the ground freezes the temperature of the soil will be pretty close to 32F. As long as the roots are underground in the frozen soil the root temperature is going to be pretty close to 32F. (Although under the arctic sea ice the salt water temperatures can drop to about 28.8F.)

Tree roots do have some ways of internally and externally protecting the cells. Yet this protection isn’t going to help much past 29F.

So would surface temperatures at -14F kill tree roots in the ground? Nope. Frozen ground doesn’t kill the tree roots because the temperature underground is near 32F. However 25F is past root cell freeze tolerance and the cells will expand and break, killing or damaging the tree. (btw Data and causes showing all this are in the Wintering Over resource in a nifty diagram).

The main reason why hobbyists worry about Wintering Over their collections safe is that the harsh surface weather can easily freeze bonsai tree roots. Ceramic pots are poor insulators and can expose plant roots to damaging cold temperatures. Ceramic material is dense and has low thermal resistance, which means it allows heat to escape the pot soil easily.

So digging the pots in ground, mulching and wetting the mulch is a good idea.

Cheers
DSD sends

 

[Christine M]

I've got a Jean's Dilly myself. Wouldn't worry about that one too much, Alberta gets pretty cold. As long as it's out of the wind and doesn't totally dry out it should be fine.

What is your situation like? You can't plant in the ground- how about placing them on the ground and mulching in? Or are you in an apartment with a balcony?

I saw a video on where else? YouTube that suggested avoiding placing the pot directly on the ground, as this would allow heat from the day sun to be absorbed from the pot. Suggested placing the pot on a brick instead.