Hi Deb, could it be Arrowwood Viburnum? I'm no pro, others here can answer better, but you could check the Google link below to see if your leaves match.

Jane

Here is a link that might be useful: Google

Dear Corunum,

Thanks for your response, but no it is not Arrowwood Viburnum... That woulda been nice! I am posting yet another photo for a different view...

Right - not a viburnum leaf....hmmm..silky dogwood? We need a pro...

Buckthorn?

Good chance it could be buckthorn? Just read how to control it. Any other ideas? Come on! Chime in. Taking this opportunity to post one more pic....

Debra, try the Name That Plant forum, they're usually pretty good at IDs. Sorry, I don't even have a guess.

Can you take one clear photo of a leaf, perhaps picking and setting it on a solid surface? I am fairly certain that it is glossy buckthorn (Frangula alnus - used to be Rhamnus frangula) an invasive small tree. We have lots of it. Easy to pull when small, but when it gets too large to pull, I wipe glysophate, generic Roundup, on the leaves. It usually takes two applications (second one when it resprouts stundted leaves) to kill it.

Last photo before I put on name that plant: Thanks for all of the suggestions!

I tried using leafsnap, from Columbia University, on my iphone, but it came up with a lot of plants that wouldn't proliferate in your area, and that had the wrong kind of fruit - magnolias, hollies, etc. It might work better for you than it did for me; it wants a shot of a single leaf, and it uses your location to decide what might grow there.

I agree that it looks like a buckthorn, or Rhamnus, but it might not be an invasive, it might be a native.

From Wikipedia (I still believe in it!)

North American species include alder-leaf buckthorn (R. alnifolia) occurring across the continent, Carolina buckthorn (R. (F.) caroliniana) in the east,...

IMO it's definitely glossy buckthorn which is listed as invasive in CT, MA, NH and VT. One clue that strongly hits at the ID is in the original post: ". . .that grows EVERYWHERE along our pond in Zone 5."

Rhamnus alnifolia is a shrub that only reaches 3' according to this website http://www.florafinder.com/Species/Rhamnus_alnifolia.php and others. Yours is clearly too tall to be R. alnifolia.

R. caroliniana isn't native to New England, only to the SE US. I don't think its berries would be ripe at this time of year as they don't ripen and turn dark until the fall whereas Frangula alnus has ripe berries now.

I deal with a lot of this as it is all over our land along the river and in disturbed areas.

Look what I found just behind my fence. It's a good 20' tall tree and I only noticed because as I walked by on the street, there were blue berries on the ground and my first thought was debra_boston. Looks like buckthorn to me. Looks like food to the birds.
Jane

Jane, yours is a wild cherry, Prunus serotina, not buckthorn. It doesn't have the prominent leaf veins on the leaf underside that buckthorn has, and the edges of the leaf are finely toothed unlike buckthorn's smooth leaf edge. The cherries have their own stem with nothing but cherries on them rather than the buckthorn's many small stems for berries off of the main woody stem/branches. If you open one up you will recognize small cherry pits, and there is a bitter cherry taste if you are brave (I think buckthorn has 2 or 3 seeds.) One of the keys is the small lines in the bark (technically lenticels) on the cherries, where the lenticels on the buckthorn are dots. The other key factor for me is when you scratch cherry twig bark it smells like almonds, while the buckthorn has its own distinctive odor that isn't easily described, but definitely isn't almond. My memory is also that the buckthorn fruits have a clear yellowish flesh under the dark skin, while cherry fruits have the dark stain in the flesh in the same way commercial cherries do.

Prunus serotina is native, and while it can be messy (the fruit stains as you would expect cherry to do) and it does seed around some, it doesn't IME outcompete and choke out other plants as buckthorn can do.

Here is a link that might be useful: Prunus serotina, wild black cherry

nhbabs Many thanks for the detailed ID. I feel lucky! We had to have an old wild cherry removed decades ago. Glad to see the species is still here - although I can't see it from the house. Your extensive botany knowledge is always appreciated, thank you.
Jane