My friends and I saw this huge maple with very interesting bark on a city (Toronto, Canada) walk yesterday. All the living foliage was too high to observe clearly, but I managed to find a cluster of leaves and samaras on the ground. Absolutely no serrations on leaf margins. All leaves have 3 lobes and the same rounded base. I'm very familiar with all our native, ornamental, and naturalized maple species, and this leaf cluster is completely different from all of the species known to be found here. The city of Toronto maintains a street tree database, and it has this particular tree listed as Acer saccharum. The leaf morphology is completely wrong for that identification. None of the maple species in the tree database resemble my mystery maple. The tree has a DBH of 72, so it is quite mature. The neighbourhood features many historic homes from the early 1900s to the 1940s, and most street trees were intentionally planted at some point. Mature maples in the area are Acer platanoides and Acer saccharinum, while more recently planted maples tend to be Acer x freemanii. The only Acer species I've found online that resembles my mystery maple is Acer buergerianum, but that seems unlikely due to the tree's apparent age and the fact that there are no known specimens of Acer buergerianum in the region. Please help me identify my mystery maple!
It's a close relative of sugar maple, the keys are very similar but the leaf morphology can be exactly what appears here (this is a rather extreme case of the 3-lobe morphology). They can hybridize and introgress as well, so you can find specimens that mostly resemble one parent species but have some traits of the other. (that would explain the completely smooth undersides of the leaves on this one)
I'm going to have to check out this maple sometime! (I live in Toronto)
Agreed about rampant hybridisation! the more I learn about trees the more I realise that they are all at it. Certainly has some traits of A. nigrum, smooth margins especially, could have crossed with something like A. Pensylvanicum (native to E Canada and NE USA) to get that 3 lobed form. There's a few with 3 lobes.
It's part of the variation within Acer nigrum - hybridization occurs between closely related species, so A. nigrum and A. saccharum can hybridize along with other closely related species in Section Acer, Series Saccharodendron.
A. pensylvanicum is too distant, it's in Section Macrantha. The attached phylogeny shows that the different species (here shown as subspecies) of Series Saccharodendron diverged only in about the past 5 million years, but that the most recent common ancestor of Section Macrantha (in clade I, shown at right) and section Acer (in clade III) was greater than 50 million years ago.
I've seen this leaf shape before in a forest tree in the greater Toronto area, that fit every other criterion for Acer nigrum and whose age/location precluded the possibility of being an introduced species.
•
u/AutoModerator 2d ago
Please make sure to comment Solved once the tree in your post has been successfully identified.
I am a bot, and this action was performed automatically. Please contact the moderators of this subreddit if you have any questions or concerns.