These are some exquisite specimens of Norway maple (or Acer platanoides) growing in the cemetery at Old St. Patrick's Cathedral, in Nolita.
For those of you who don't live in New York City, I cannot impress upon you how rare it is to see a huge, spreading maple tree outside of Central Park. The walled cemetery has protected these trees well.
A couple weeks ago, we looked at sugar maples which, at first glance, can seem quite similar to Norway maples. The margins are entire, but Acer platanoides leaves are usually much larger, change color later in the season and change to a yellow hue, whereas Acer saccharum leaves are smaller and can turn yellow, orange and red.
The other undeniable difference between the two maples is in the leaf's petiole. Snap a leaf off a branch of the Norway maple and you will find the exuding sap is white. The sap on a sugar maple runs clear.
Here's a shot through the keyhole of the cemetery doors.
If we got a bit closer to the trees' trunks, we may find that the grass is not growing as vigorously. That's because Norway maples are allelopathic. Allelopathy (or more specifically, negative allelopathy) is a phenomenon where the maple can produce chemicals that limit the growth of other plants in its rootzone. For this reason, the non-native Norway maple is deemed invasive. Plants cannot grow beneath its canopy and thus the plant has more opportunity to spread. The dense shade of this larger-leaved maple amplifies this situation. I discourage students from utilizing this plant for these reasons.
Finally, though, I'll end on a light note. I've mentioned my aunt before, and that I tinker in her garden a bit. She has a large red-leaved cultivar of Norway maple in her front yard. When she bemoans the sad state of her lawn I remind her that the maple isn't helping things and she feels better. A couple months after we discussed this, she brought it up again and called the tree her Norwegian maple. Nowegian Wood, I get. Norwegian maple...not so much!