American Hornbeam hardiness question

[karen82]

This is more of a general hardiness question actually. Most species have a large hardiness range. Does this range just indicate where the species is found, or the extremes any individual of the species can tolerate?

I'm asking mainly because of an American hornbeam I purchased though. They are species that is hardy in zones 3-9. I live in zone 5. This tree was collected in zone 8. Since it was growing in zone 8, is it best to assume it's not going to be hardy in zone 5 even though it's a species where at least some individuals can live in zone 3?

I'm torn as to whether I should treat it as a zone 8 tree (let it freeze lightly a few times, then move it to the greenhouse), or as a zone 5 - overwintered completely outdoors in a sheltered spot, like I do for my trident maples. Or can it just be treated as a full zone 3 and be set on the ground and ignored all winter.

 

[hinmo24t]

I have a few collected from MA/RI...was planning to keep in breezeway outside, lightly mulch topsoil, keep slightly elevated.

If a known windstorm or frigid stretch comes about I can put in garage for a few days where it'll still be freezing

Mine might be hophornbeam


Goodluck

 

[Tums]

I think the original location does have some impact on hardiness so I would at least treat it like your tridents. Potted plants are always harder to overwinter anyway compared to in ground plants.

 

[Dav4]

Provenance is important… I wouldn’t expect a tree collected in the warmest part of the species range to be fully cold hardy in the coldest part of it’s range. With that being said, its genetics will likely allow it to survive in the middle… . I know that bald cypress is collected in Louisiana and South Carolina are fully cold hardy in northern Illinois and Ohio even though they don’t grow naturally in any climate that cold. Does this mean that you’re hornbeam Will be fine in zone five… Time will tell. I would probably give it decent winter protection either way, heavily mulched for sure… a cold frame would be ideal. Good luck!

 

[atlarsenal]

What @Dav4 said . I would treat it the same as your tridents.

 

[Jzack605]

As said provenance is important but that doesn’t mean acclimation is impossible.

 

[Cable]

As said provenance is important but that doesn’t mean acclimation is impossible.

True but I've read some surprising (to me) studies which have shown some trees never acclimate beyond their provenance. It can even be as extreme as a normally sun tolerant tree which grew wild in the shade and never handles sun well no matter how hard you try to acclimate it.

I'm not sure if some growth habits (like cuticle thickness) are just set in the seedling years or of it is as simple as natural selection and only ones genetically able to survive the conditions grow and therefore aren't able to adapt to changing conditions.

 

[karen82]

Well it's hard to decide what to do. I guess I will probably treat it like my tridents and bury it along the side of the house - though the lazy part of me is tempted to keep it in the cold greenhouse instead as it's such a hassle to winterize trees.

 

[karen82]

This is more of a general hardiness question actually. Most species have a large hardiness range. Does this range just indicate where the species is found, or the extremes any individual of the species can tolerate?

I'm asking mainly because of an American hornbeam I purchased though. They are species that is hardy in zones 3-9. I live in zone 5. This tree was collected in zone 8. Since it was growing in zone 8, is it best to assume it's not going to be hardy in zone 5 even though it's a species where at least some individuals can live in zone 3?

I'm torn as to whether I should treat it as a zone 8 tree (let it freeze lightly a few times, then move it to the greenhouse), or as a zone 5 - overwintered completely outdoors in a sheltered spot, like I do for my trident maples. Or can it just be treated as a full zone 3 and be set on the ground and ignored all winter.

Well I answered my question here. I ended up treating my zone 8-collected American hornbeam the way I treat my zone 5 plants (sheltered spot in my yard) and it died.. mostly at least.
Its neighbors in storage all survived - some of the Tridents had a bit of die back on longer shoots but otherwise no problems.
But the American hornbeam didn't make it. All of its buds are dry and brown and flake off easily when brushed and there is no green on any of the smaller branching. A few of the larger branches have a green tint to the bark so I have some hope it may partly survive, but so far (about 2 weeks out of storage), there are no signs of any live buds. I'm very disappointed since it was a nice pre bonsai.

 

[karen82]

A small update, the hornbeam lost ALL branching but sprouted from the trunk and grew pretty well over this summer. I've just been watering it well and letting it grow freely and it seems pretty happy. I will probably overwinter it in the greenhouse if I can make room for it since I don't want to risk losing branching again. For the record, last winter was a pretty mild zone 5 winter, I was surprised to find it lost branches so easily.

 

[Vincent Tanner]

Thanks for this info! I appreciate you sharing this experience. I’ve got a couple hornbeams (one European, one Korean) from a nursery in California… but I’m zone 6 here in RI. They’re *allegedly* cold hardy. I was gonna just heel in / mulch outside, but maybe I’ll take them into the unheated garage just to be safe.

 

[penumbra]

I don't have American Hornbeam, but I do have European, Korean and Japanese. They have all done well with no winter protection at all in my zone 6 location.

 

[Paradox]

It's my belief that taking a tree from a couple of zones away needs time to acclimate to the new climate as long as the new zone is within its acceptable range. This can take a couple of years.

Also in general, you need to treat a tree in a pot as if it were less hardy to where it is by one zone. So if a tree is stated to be good in zone 7, once it's in a pot, figure zone 8.

 

[penumbra]

This is exactly right ^^^, I should have mentioned it.