Japanese Maple in Minnesota Winter (USDA Zone 4a)

[turnyface]

I received a Japanese Maple (Mikawa Yatsubusa) as a gift. The tree is young and still in a nursery pot. I'm thinking ahead to what to do over the winter.

I'm in zone 4a.

I do have an attached, unheated garage and wondering when is the best time for me to move it into the garage?

Do I wait until average low temps are in the 20s Fahrenheit before I move it into the garage?

Do I take it out when average low temps return to the 20s Fahrenheit?

I suspect it'll need to stay in the garage from early December to early March. I've done a lot of reading, but nothing definitive for my particular situation.

 

[Shibui]

Adding a general location to your profile may help alert some other Mn members to drop in and put up their experience and advice. It also pops up every time you pots to alert us to your specific needs if you post again.
Not much use me offering advice. We never see anything approaching 20F so all my trees, except tropicals, stay on the benches all winter.

 

[rockm]

These are perhaps the best short concise overwintering info I've seen.

The prep vid is pretty long, but bottom line, leave the maple out on the ground to get hit by at least a couple of freezes

Consider this info about how much protection you need to give the tree. I'd go with the garage option, Zone 4 is a bit dicey for Japanese maple.

 

[turnyface]

Adding a general location to your profile may help alert some other Mn members to drop in and put up their experience and advice. It also pops up every time you pots to alert us to your specific needs if you post again.
Not much use me offering advice. We never see anything approaching 20F so all my trees, except tropicals, stay on the benches all winter.

Thanks for the suggestion. I've updated my profile!

 

[turnyface]

These are perhaps the best short concise overwintering info I've seen.

The prep vid is pretty long, but bottom line, leave the maple out on the ground to get hit by at least a couple of freezes

Consider this info about how much protection you need to give the tree. I'd go with the garage option, Zone 4 is a bit dicey for Japanese maple.

Thanks! I'll have to give both of these a watch!

I must have looked at an old map. I'm now seeing the updated USDA plant hardiness map and the Twin Cities metro is zone 5a. Is zone 5a also dicey for JM?

 

[turnyface]

Since I'm in zone 5a, I wonder if I can just build a cold frame and let it sit on my deck for the winter.

 

[Gabler]

Since I'm in zone 5a, I wonder if I can just build a cold frame and let it sit on my deck for the winter.

I wouldn't. I can barely get away with leaving them outside in zone 7b. The species is really better suited to climates with both mild winters and mild summers, like the temperate island climate of their native Japan. England and Wales seem to be good for them, too. Really any place buffered against extreme hot and cold by favorable ocean currents.

The roots are the problem. They are far less tolerant of cold than the top. That's fine for a tree planted in the ground with roots buffered against the cold air, but a tree in a pot has no such protection, especially up on a deck. You're going to need good winter protection.

 

[Dav4]

Since I'm in zone 5a, I wonder if I can just build a cold frame and let it sit on my deck for the winter.

By definition, cold frames are structures built on/in the ground to use the earth as an ambient heat source to mitigate severe temperature swings. A structure built on an elevated deck, having no connection to the earth, will be 100% subjected to ambient air temperatures. There aren't many trees whose roots can survive -20 F temperatures, and certainly, Japanese maples won't. In my experience, they're actually quite suited to areas with real winters, but your winter is borderline too harsh, so they'll need robust winter protection.

 

[Paradox]

Thanks for the suggestion. I've updated my profile!

Sorry, but can you put the state?
I'm from another part of the country, snd maybe I'm dumb but I have no idea where "twin cites metro" is.

"Twin cities" for me is somewhere in Maine

 

[turnyface]

Sorry, but can you put the state?
I'm from another part of the country, snd maybe I'm dumb but I have no idea where "twin cites metro" is.

"Twin cities" for me is somewhere in Maine

Fixed

 

[turnyface]

Lots of great information already. I’m going to watch those videos and make a game plan, but I very much appreciate everyone’s help!

 

[Gabler]

Twin cities - Wikipedia

en.m.wikipedia.org

I can see where that would be a source of confusion.

 

[turnyface]

 

[Paradox]

Remember, if you keep it inside your garage over the winter, you'll still need to check it for watering needs. It won't need water nearly as much as in the summer but you don't want it to dry out. If the pot freezes solid though, then it will need even less

 

[rockm]

"I do have an attached, unheated garage and wondering when is the best time for me to move it into the garage?"

As long as the garage stays reliably above 20 F or so, this will work once the tree is dormant. It is important the tree get hit by short freezes and frosts in the fall---make sure it's nothing below 25 F or so. I store all my trees in ate Nov. around Thanksgiving after at least two hard freezes. The temp exposure "hardens off" the roots in prep for the coming cold. Don't make the mistake of trying to coddle trees avoiding all autumn weather (And BTW, you probably know this tree should remain outside all the time. Indoors will kill it).

Once the leaves have dropped, put it into the garage. You will have to monitor the pot during the winter to insure it doesn't dry out. Dry roots in the winter means a dead tree in the spring.

 

[Gabler]

View attachment 551553

To the extent that a bonsai tree is a tree in a pot, you technically have a bonsai tree. However, it hasn't been styled in the Chinese and Japanese tradition of bonsai.

For starters, I would recommend you fatten up that trunk. You thicken a trunk by growing out the tree and then cutting it back down to size when the girth is sufficient. To that end, I recommend you plant this tree in your yard and let it grow big and fat until it's ready for bonsai training. From time to time, you'll do some maintenance work on it, but overall, your goal is to get it growing as fast as possible at this stage.

That said, wait until early spring next year to transplant it. At that time, you'll want to sort out the rootball to remove roots that circle around the trunk or otherwise overlap another part of the tree, as well as roots growing straight down. Keep it watered from time to time in the first year while it gets established, and then watch it take off and grow fast in the second year.

The other option is to keep it as it is and enjoy it as a patio tree.

I realize that isn't exactly the question you asked, but your plans for the tree will inform your winter protection choices.

 

[turnyface]

To the extent that a bonsai tree is a tree in a pot, you technically have a bonsai tree. However, it hasn't been styled in the Chinese and Japanese tradition of bonsai.

For starters, I would recommend you fatten up that trunk. You thicken a trunk by growing out the tree and then cutting it back down to size when the girth is sufficient. To that end, I recommend you plant this tree in your yard and let it grow big and fat until it's ready for bonsai training. From time to time, you'll do some maintenance work on it, but overall, your goal is to get it growing as fast as possible at this stage.

That said, wait until early spring next year to transplant it. At that time, you'll want to sort out the rootball to remove roots that circle around the trunk or otherwise overlap another part of the tree, as well as roots growing straight down. Keep it watered from time to time in the first year while it gets established, and then watch it take off and grow fast in the second year.

The other option is to keep it as it is and enjoy it as a patio tree.

I realize that isn't exactly the question you asked, but your plans for the tree will inform your winter protection choices.

Would it be an option to pot it in a larger pot early next spring? I don't have the ability to pot it in the ground, but would like to grow it for several years to thicken the trunk before I start working on it.

 

[Gabler]

Would it be an option to pot it in a larger pot early next spring? I don't have the ability to pot it in the ground, but would like to grow it for several years to thicken the trunk before I start working on it.

I use large pots. It slows down the growth, but I can take trees with me more easily when I move. When this real estate market cools off, and I can buy a house, I'll start putting more trees in the ground.

 

[dbonsaiw]

Would it be an option to pot it in a larger pot early next spring? I don't have the ability to pot it in the ground, but would like to grow it for several years to thicken the trunk before I start working on it.

For sure. Grow boxes are great as well, and you can make them whatever size you want. I've had really nice growth in wide and flat grow boxes. In fact, I have a dawn redwood that is approaching 20 feet tall (almost 3" base") in a very large grow box (roots have escaped into the ground) - this is my third year with it and I got it as a little stick. The JMs do well also.

FWIW, I've been following Rockm's advice on overwintering for a few years now and the trees are doing well through the winter. One of the most important things he taught me was that dormancy is an extended process starting in the summer. You don't want your trees staying nice and toasty - you want it to ease into dormancy slowly in your climate to trigger its natural responses and get itself prepared for real cold. JMs can handle and actually want/need winter. It's just when the temps start dipping into the danger zone for JMs that you want to be thinking about places where the tree can stay cold and dormant, but protected from desiccating winds and extreme temps.

 

[Grunge_Bonsai]

Adding a general location to your profile may help alert some other Mn members to drop in and put up their experience and advice. It also pops up every time you pots to alert us to your specific needs if you post again.
Not much use me offering advice. We never see anything approaching 20F so all my trees, except tropicals, stay on the benches all winter.

I was nudged about this on another post and took it the wrong way. I am guessing this is really key to getting good info on this site!

Learning as always. . .