I wonder how big these can get. This reminds me of a very mysterious broadleaved tree I stumbled upon in northern Cecil county about a week ago. Still in deep green leaf - but clearly not a BLE - when practically everything else had lost most of its leaves. Especially this year! Even that particular type of red oak that is very late turning red, was mostly finished. There are some of those up there near the Mason-Dixon border. I wondered if it could be a late/semi-evergreen strain of Ulmus parviflora, but the bark was 100% not right for that. It had an elm like shape and was at least 40, maybe 50' tall though.

I should make myself drive back up there...

I should make myself drive back up there...

We await your report ;)

Easy to spot and kill, I suppose

It's everywhere.

There're areas I've driven for miles in a variety of places, and almost continually, you could see green leaves filling the woods. from the car, after all the other tree's leaves have fallen.

Even if you cut and treat the existing stuff, there's generally enough seeds in the ground to start hedges of them growing up in no time. Not to mention the birds carry the seeds to new places every year. Basically, naturalized here. They appear shade tolerant.

I've never seen any larger than ~4" caliper and 20 ft. tall, at least in my area.

I havent done much 'googling' about this but as I recall Buckthorn were brought to NA from Europe. So assuming they are native to areas of Europe, how are they kept in check naturally? .

I’ve attempted to kill a few trees that have grown near my house; cut the tree down,

"Mine" are all over the adjacent public park. And so when no one is looking ;) I will use a handsaw (my chain saw would be too noisy) and I cut off what I can. That wood is way hard. It will invariably sprout back at the cut but the next year I will cut it back again and often it will die by a "thousand cuts" ;).

Rouge your "death of a thousand cuts" has actually been listed as a 'newer' method of control. If you're interested look for the "high cut" or "high stump" method. Basically the tree is cut at approx. 4-5 ft up in the spring after leaves have grown. In late summer/fall remove any regrowth. Next Spring after leaves form, remove any which show and the plant typically dies after 2 years. Sounds very similar to what you have already discovered.

Interesting @katob Z6ish, NE Pa...thank you.

If you look in the picture above you will see a couple of 'stumps' courtesy of moi ;).

I've been battling this plant for close to ten years on the almost four acres of woods surrounding the house and garden. When I first got here the wood lot was choked with this pest, including trees approaching twenty feet. Garlon was effective as a basal treatment, and the larger Buckthorns were removed first. The bigger problem was the smaller plants blanketing the woodland floor.

I began a fall foliar spray regime, but found I was killing all the small pines and oaks, which were struggling to regenerate under the heavy cover of Buckthorn. In an act of pure enlightenment or craziness, I am now cutting any remaining Buckthorn with a handheld brush cutter, trying to avoid oaks, pines, and Balsam firs, which to my surprise were plentiful. Red Maple seedlings are often a casualty, but they seed so readily I'm not too worried about them.

This work is tedious beyond belief, but it gets easier each year. When battling Buckthorn, it's best to look at it as a lifestyle.

Here's a thread from a few years ago.

" I haven't done much 'googling' about this but . . . they are native to areas of Europe, how are they kept in check naturally?"

Good question, and even after googling it's difficult to find much info on the subject, but a webpage from the USDA Forest Service (FEIS) appears to confirm that buckthorn doesn't seem to be as problematic in Europe as it is here, " . . . scientists who have observed common buckthorn in mainland Europe report that large, dense thickets do not usually occur"

The Minnesota DNR has an article on the Biological Control of Buckthorn that indicates that there are insect herbivores that help keep buckthorn in check in its native range, "Over 30 specialized insect species have been recorded on common buckthorn in Europe. Many of these potential biocontrol species were studied and ruled out due to lack of host-specificity"

Common (European) buckthorn is definitely one of the worst invasive plants in the Great Lakes region. As maackia said above, "When battling Buckthorn, it's best to look at it as a lifestyle." For those of us involved in controlling it as part of our job, you could also call that "job security" ;)

Why it's invasive for you and not for us is a good question. In fact I don't see it very often at all. Another example is Callery pear. It's not native here but widely grown as an ornamental. But it hasn't escaped and I've never seen a seeding.

Oh well, felt like killing some time today. Good news is I was able to locate it - northern Cecil County has a web of little country roads I'm not very familiar with and I wasn't sure I could find it again. It's such a rural area there's no street view so I couldn't search for it ahead of time, just had to hope I could remember my drive. Bad news is, sun was setting behind it so I couldn't get a good picture, I had to drive down the road a bit to get a more distant view from the side. Also I wasn't going to stay for long either, and risk raising someone's suspicions and making them get their gun hahaha.

I can try to get a better pic later, but I feel like we ought to be able to figure out what this is.

One thing's for sure, it's a huge outlier. My neighborhood near the water *just* had its first hard freeze a couple nights ago, but this would have seen a hard freeze at least a couple weeks ago. There are NO other trees anywhere near it, holding onto leaves. I even drove past an intersection I remember having a late-holding red oak of some kind...it didn't have a single leaf on it anymore!

The bark is a bit shaggy so, even though the rest of it doesn't look one bit like an American holly, that would rule it out anyhow. I cut out their vehicles just below this picture, for their privacy, but you can see it's definitely close to 50' (large pickup truck just below the bottom of pic)

Some Celtis or Phellodendron might hold their leaves late, right?

I wonder if it could be one of these: https://www.gardenweb.com/discussions/6445847/mystery-ble-planted-in-parking-lot-of-merrifield-garden-center-nova

If so, a giant!

Rouge, I've always assumed CDN meant "Canadian" but can you be a little specific about where you are?

Hey 'david', we are in Southern Ontario.

davidrt28 - at nearly 50' tall I think it's pretty unlikely to be a buckthorn or a Chinese fringetree. We definitely need a better photo. Were you able to tell anything about the leaf shape from that distance?

Nope. It's pretty far into someone's back yard so, short of becoming friends with the owners, we're going to have to work from this distance. Next summer (I assume it will lose leaves soon!) I could go back with a telephoto lens on a real camera.

Not to overdramatize it, but this is one of the biggest horticultural mysteries I've experienced. I've just never seen a tree like this around here...around here meaning, anywhere on the east coast north of the Gulf states!

It's definitely a lighter, ashen green, vs. a deep shiny green if this were some kind of (utter shocking hardy mutant) giant Michelia type magnolia or something. More plausibly, also doesn't look like ANY tardily deciduous oak I've ever seen, though, let's not rule that out. Let's narrow it down to known tree genus that could contain very tardily deciduous species at all.

Acer

Celtis

Ulmus

Fraxinus

Quercus

Are 5 that come to mind at once. There are a lot of people around here who have moved with the military because APG is nearby...how crazy would it be if someone from the SW or Socal brought back a seed of a favorite ash tree, which was a hybrid of a green ash (perhaps an example of an eastern tree that is planted in those areas for some reason) and a mexican Shamel ash. It could be just barely zone 7 hardy, and very tardily deciduous. Far fetched, but...like I said, this is stumping me. (of course, then the mystery would be why it survived EAB! Are any Asian ashes semi-evergreen? If so how would something so ridiculously rare end up in a very middle class back yard in a notably non-horticultural part of the country?)

It will probably prove to be something obvious, but nothing obvious comes to mind! Duh!

Maryland's excellent online public records to the rescue: current couple have only owned the house 15 years, so I think the tree likely predates them. Googling past owners for any evidence of extensive travel...it's a longshot but I've been surprised what I can find out about people.

Update: typical Cecil county demographics. I have determined that whomever planted the tree < 2010 is almost certainly dead. No seeming history of being in the military or of traveling much. Guy who owned the house in the 2000s was a welder at the former Chrysler plant in Newark, Delaware. That IS across from the Udel Botanic Gardens! 🤣 But I've never seen a tree like this, there, although I don't visit too often.

If the sun's out tomorrow morning, might tree driving by again when the sun is positioned in a better way. I can maybe find some binoculars and hope there are no cars in the driveway.

interesting discussion, here in Switzerland/ Southern Germany I wolud rate Rhamnus catarticus as a slow growing shrub, probably moisture loving, slow growing, not very tolerant to pruning, not very competitive.

But things change in a new eco system. I read up on Solidago canadensis, which is a problematic invasive plant here, has to do with its own chemestry and the exchange with soil microbes etc.

No clue what it is, but from the pic, to me, the leaves look simple and very long. Might no be so , but seems to me

Yeah that is the way they look to me, too.

The 'Occam's Razor' if I just knew 'there's an extremely tardily deciduous in the mid-Atlantic/upper South of the Eastern US tree' would be something of the Oak persuasion, yet it just doesn't look right for that.

I gotta work up the courage to go by there...stay tuned.

I started another thread about this, but it got shadow banned for some reason. I drove down the driveway and knocked on the door. Nobody came to the door, so I couldn't go into backyard, but at least I was able to get a little closer. It clearly has pinnate leaves. A pecan comes to mind, but it just doesn't look quite like other pecans I've seen.