Overwintering Trident Maple in Zones 6 and 7

[miker]

I could not find a dedicated detailed thread on overwintering Acer buergerianum on here, so I thought a thread addressing this topic might be helpful, no that we are well into fall.

Since I have recently relocated to the warm zone 6b environs of SE PA, I need to become an expert at keeping my trees safe and properly dormant over the winter.

The tree that I am most concerned about is my trident maple as the species has a reputation for being tender for a temperate tree as many books and online sources attest to. One source claimed that if wintered in a pot in zone 6, the roots would turn "to mush", indicating what I read before that trident maple roots are fleshy and hold a lot of water and thus tend to rupture when they freeze.

My plan for my smallish trident is to keep it completely out in the open (out of the sun once bare of leaves) and unprotected during temperatures 25F +, then around December 1, put it in a portable (14"X 14") wooden box, open on top, filled with lightweight mulch or substrate to about 1" above the soil line. This will be kept either against the north side of the house or in a small unheated shed when nights go below 20F or so. When we get the 5-10 nights a year below 10F, I will put a small space heater in the shed to keep it from going below 20F. Should this keep a trident maple safe and wintered properly? Basically, keeping the root zone from going below 20F. Or will I end up with mushy dead roots and a dead tree come April?

Growers of trident maples in zones 5-7, what do you do to keep your trident maples safely and properly handled for winter? What is the absolute minimum safe root temperature?

If I know what the minimum safe temp is and my tree is in a portable wooden box, I can just move it around even a couple times per day to keep temps 20-50F.

 

[miker]

Another tree I have is the unusual Acer buergerianum var. formosanum. My gut tells me that I might want to treat this as a subtropical(maybe like a live oak?) when it comes to overwintering. Perhaps the best bet would be to keep the tree 30F -60F until spring and it should both not be killed by lethal cold and should get way more than enough chill hours, considering it is from the higher elevations of Taiwan.

 

[M. Frary]

December 1, put it in a portable (14"X 14") wooden box, open on top, filled with lightweight mulch or substrate to about 1" above the soil line. This will be kept either against the north side of the house or in a small unheated shed when nights go below 20F or so

Why not do this from the get go.

 

[miker]

Well since (based on looking at data from past winters) we may not get below 25F or so until after November here, I figured I would have a plan in place but leave the trees where they are if temps will be 25-65F for the next month plus. It would seem silly to mulch them in and make direct observation difficult before it becomes necessary.

 

[Dav4]

I kept my tridents along with many of my other trees inside my unnattached garage in zone 6 se MA for several years without issue. They were placed on the floor and mulch applied around and over the pot, usually at the end of November. The mulch and pots were watered well and left to freeze solid by the end of December and hopefully stay that way until late march. Temps in there easily fell into the teens and single digits on occasion. The issue, I suspect, isn't the fleshy roots being prone to freeze damage, but that tridents may require less chilling hours to complete dormancy and tend to wake up earlier and be damaged by late winter or early spring cold. This is just my opinion, mind you. Siting them carefully so they stay cold as long as possible is most important, along with protecting the roots from extreme cold and multiple freeze thaw cycles.

 

[Paradox]

My trident goes in my attached, unheated garage in zone 7. They arent as cold hardy as some.

 

[whfarro]

I don't have tridents, but all of my maples go into my attached, unheated garage for the winter. I check them often. I pile snow on top of them and that allows for a kinda slow release watering as it melts on warmer days. My thinks I totally lost it when I shovel snow into the garage...lol

 

[miker]

Thank you for the responses. I am considering keeping mine as cold as it can get on a shaded and sheltered northern exposure, but 25F +.

Or just putting it in an attached garage or shed(that is well insulated with a real roof and a window) so the shed stays on the warm side. I would put it inside here anytime the temperature is 40F or less and outside above 40F or so. I am willing to move the portable enclosure my trident will be in quite a bit since it is just one tree, to make sure temps stay between 25-50F. Above 50F, which happens periodically in the winter here, and the tree goes in the garage.

I will probably put my Formosan trident in with my plain trident as I think this approach will work for both.

 

[miker]

Okay, so everbody who has seen many of my posts knows my little trident is my "special project". My plan is for it to sit completely exposed and unprotected on a 3 foot stand in the middle of the yard until around December 1, around which time it will go into a wooden box with a detachable top and pine bark mulch up to 1" above soil level. This will be moved around as I see fit to keep it constantly cold, but not much below 25F at the rootzone.

The beginning of this weekend is forecast to have our first advective freeze, with lows 28-30F and breezy. Will this have any chance of killing outer roots touching the inner edge of the pot, or am I just being overly cautious? If we were to see 4-5 hours slightly below freezing and breezy conditions, I could see the rootball freezing solid.

Maybe I should actually just set the tree in the attached car-less garage and forget it (except watering of course). It may only get as much winter cold as Atlanta this way, but even this is plenty for a trident maple.

 

[Dav4]

Okay, so everbody who has seen many of my posts knows my little trident is my "special project". My plan is for it to sit completely exposed and unprotected on a 3 foot stand in the middle of the yard until around December 1, around which time it will go into a wooden box with a detachable top and pine bark mulch up to 1" above soil level. This will be moved around as I see fit to keep it constantly cold, but not much below 25F at the rootzone.

The beginning of this weekend is forecast to have our first advective freeze, with lows 28-30F and breezy. Will this have any chance of killing outer roots touching the inner edge of the pot, or am I just being overly cautious? If we were to see 4-5 hours slightly below freezing and breezy conditions, I could see the rootball freezing solid.

Maybe I should actually just set the tree in the attached car-less garage and forget it (except watering of course). It may only get as much winter cold as Atlanta this way, but even this is plenty for a trident maple.

Nah, the tree needs multiple frosts and light freezes in the early to mid fall to maximize it's cold hardiness. I'd consider protecting the roots if temps were forecast to fall into the lower 20's, otherwise you're good.

 

[petegreg]

I've been wintering my only trident put in the ground with its pot and mulched for 6-7 years. Zone 6A, lost no single branch. I guess from what we can read that only roots need some level of protection here... SFSG.

 

[lightwatchertoo]

Miker, I live within a few miles of you.
I overwinter my tridents in my attached garage.
The temperature is usually in the 40"s but does get into the 30's at time.
This has worked well for many years.