I have noticed this in both states I’ve lived in - Ohio, and Maryland…
It’ll be around this time of year, when the vast majority of trees have either lost all of their leaves, are well on their way to doing so. But there’s that one tree sticking out that’s still almost completely green. And I’m not talking about trees that always stay green late, like sawtooth oak, but one where most specimens of its species are well on their way to dormancy, but this one is a hold out.
When I was a student at the University of Akron, there was an English Oak that stayed completely green well into December, and in that climate, most years the leaves ended up getting frozen in situ while still green, and then grudgingly dropping off by the new year. It seemed that temps below 20F were necessary to kill the leaves.
Here in MD, there is a Platanus that does the same, it’s still deep green when most others are bare, or at least brown/yellow. It usually holds out until early December as well unless a hard freeze does the job first.
We have a few trees that hold many of their leaves almost until new ones arrive (Water Oak). These make cleaning up the yard difficult.
It is an issue for me with apples, which when young and scab and CAR free will hold their leaves until we get 10 degrees. Usually we get wet snow immediately before that, so it always worries me that young branches will break under the load. Also with apples I have the hypothesis that abscission-related genes are poorly expressed in our cultivated varieties, as abscission of the fruit isn’t a very useful trait, so they hang to their leaves longer too.
I always considered this a “the species is not native” indicator here in the north. Callery pear and honeysuckle do this here. Both are invasive, non-native species. I’ve also noticed it on Kentucky coffeetree and black locust, but those have their foliage killed after a hard freeze. Those two are native to the US, but not Iowa. Or at the least coffeetree is probably entirely seed-sourced from more southern stock.
It’s mostly due to provenance, indeed.
never seen leaves stay green here beyond nov. but beech and oak can stay on dead throughout the winter.
Betula nigra (river birch) does this sometimes as well.
Northern Red Oak and American Hop Hornbeam both will hold leaves until spring here. A.H.H. will not unless they are grown in full sun it seems. N.R.O. will hold leaves in full sun or shade.
In answer to the original question, I would suggest the variability is usually genetic when concerning non-clonal trees. Of course, when it involves clones behaving differently, I will attribute that to environmental differences, perhaps something like drainage differences.
At any rate, logical explanations are easy to come by and difficult to prove.
I have a tale of two Damson plums that stand in the same soil very close to one another. One is a dependably annual bearer and the other one is not. I’ve never thinned either tree.
There is a chance that soil conditions vary in a way I can’t see, but that is as close to a logical explanation I can construct.
I can come up with a dozen of these anecdotes. Sometimes it’s nice not to have an explanation.
I have 2 peach trees about 3 1/2 ft tall that has not lost their leaves yet. Is that normal? I have had weather in the 20’s with numerous heavy frost plus 2 inches of snow.
Yes my baby apple trees (1st leaf) refuse to drop their leaves. So I can’t rake them up yet ugh… and it is in the low twenties as I write…
My temps have dropped to about 7 and many apple trees have brown leaves sticking to the trees right now. The Goldrush apples no longer look appetizing.