That is perfect. Thank you GG48.

You are most welcome :-)

Even in my very mild winter climate, I need to be careful with my collection of containerized Japanese maples if the temperature takes an unusual drop into the low 20's. JM's are more sensitive to cold than other maple species but there are very few trees of any kind that could withstand a zone 5 winter in a planter or container. It just gets too cold.

Of course you can say pretty much anything you like. Maybe the client will buy it. Maybe the client knows better :-)

I think the official 'frost line' here is below 5 ft. That's how deep you have to put foundations and plumbing so they don't freeze when the surrounding soil freezes. So anything that grows here has to be able to handle frozen soil. This goes double for anything that self-seeds, since small, young plants aren't going to have the root system to get below even a moderate frost line.*

Being reasonably lazy, I don't tend to clean out old containers until I want to reuse them. So I have done inadvertent experiments in whether or not squirrel planted trees can survive over winter outside in pots in zone 5b. Yep, they can. The current experiment is whether or not they can survive a drought in pots without being watered. Hopefully not, but that one hasn't ended yet.

I'm assuming the reason you don't want to do this is because sugar maples get big, and you have to be a Rockefeller to afford pots that large.**

*This is a big issue with fall planting of evergreens. It fails often since they do transpire water, but don't have access to it in frozen ground.

**I don't remember if they are maples, but the entrance allee to Kykuit consists of large trees that are in incredibly large 'pots' since they are over the underground garage.

I may be missing something here but will argue to a point. Sugar maples get big and are yard trees, not pot trees.

That said, I have had a couple dozen metasequoia survive a winter or two in pots, not even big planters. My "set up" mostly consists of hiding them in a sheltered location and maybe dumping leaf litter on and around the pots. Metasequoia isn't more winter hardy than sugar maple.

Now the ground is better I agree, I just want to say I expect 100% of Metasequoia to survive winter in ground but maybe 90% in pots so I'd expect similar with sugar maple.

the other issue.. if there is pot freeze.. is snow melt or spring rains on a frozen pot ...

dormant plant need little moisture .... just dont let the media go bone dry ... but roots need air as much as water .... and if you freeze the root mass into an ice cube... then plants can die.. root root is possible ...

one other thing.. is how pots can come out of dormancy months early.. and then go back to dormancy.. etc.. the trick is get stuff dormant.. and keep it dormant.. none of this back and forth in and out of dormancy ...

bottom line.. its just a giant PIA.. and really not worth the possible loss of investment ..

all that said.. who is going to grow a 50 foot maple in a pot???? .. thats just nuts ... what would you need.. and 8 by 8 foot planter???

ken

ps: bonsai is an option.. but you didnt mention it ...

ANY size tree can be grown in a planter or container. How large it might grow will be dependent on the size of the container. Containerizing the tree (or shrub) is an automatic dwarfing process.....if confined to a container or planter, the tree will never grow to the same size it would in the ground where root expansion is unrestrained. The smaller the container, the less size the tree will attain compared to inground growth.

Can you grow a sugar maple in a container?? You certainly can!! But don't expect it to get 50' tall!

It is also important to know that root tolerance to cold temps can vary widely by tree species and has only a tangential relationship with how cold tolerant the tree might be if planted in the ground. Exposure of the roots in a containerized tree to temperatures far below what they would experience in even frozen ground soil can be a seriously limiting factor in winter survivability.

Thank you for everyone's input. Educating my client facilitates healthier decisions on our site.

The info puts me exactly where I need to be. There are options - as always. I will talk my client into transplanting the Sugar Maples into the ground after they have served a purpose as decor in a cemented venue (in pots). I don't have proper protection for them in the Winter. The Maples are currently 10'-15' high and the root ball is still manageable.

I can't have trees be sent to death when it can be helped.