the birch

I was planning on writing a bit on Nandina domestica (Heavenly Bamboo), but the shots I took quickly on Sunday aren't quite up to the quality I'm holding myself to so I think I need to spend a little more time on that first.

However, did take some other photos over the weekend while preparing for a lab on native trees I'm teaching this semester. Though I took these more to emphasize easy identification characteristics instead of the ornamental appeal of the plant, I still think it's a good excuse to talk a little bit about one group of our native trees: the birches.

Paper Birch (Betula papyrifera)
Note the cluster of three male catkins on the end of the branch

The Paper Birch is probably the first one that comes to mind when I think of a birch tree. It's actually one of the first trees I remember being interested in as a kid. Growing up on the Vineyard I was used to seeing Black Oaks, White Oaks, Pitch Pine, Sassafras, the occasional Red Maple, and that was about it. I saw one while up in Maine one summer, and remembered being confused over how different it was than any tree I'd seen before, with the thin, papery white bark smooth and cool to the touch. Maybe still as a result of this, like many birches, I'd probably claim the bark is the most significant feature of this tree.

So if that's the case then why did I relegate it to the background in the above photo? I didn't even widen the depth of field enough to bring it remotely into focus. Well, I was trying to highlight a group of catkins (essentially clusters of petal-less flowers), as they serve as a good characteristic to distinguish it from a similar species, the Gray Birch.

Grey Birch (Betula populifolia)
With a solitary male catkin

The name Grey Birch typically refers to the bark of this species, which is evident in the photo above mostly because of the lighting. If you see these plants out in the woods together though, sometimes both the Paper Birch and Grey Birch will have sort of an off-white color to the bark making them hard to tell apart. However, on this tree the male catkins tend to be solitary, instead of clustered as in the Paper Birch.

Yellow Birch (Betula alleghaniensis)

You might also see female catkins on birches, which are a bit stouter, and generally not on the tips of the branches. If you're in doubt over whether you have a male or female catkin, try rubbing it back and forth with your fingers. The female catkins will break apart rather easily while the males won't. And of course, there are male and female catkins on this tree as there are independent male and female flowers.

Now for the next three I actually do have the bark in full focus. First up is the Yellow Birch, or Betula alleghaniensis. The botanical name of this changed at some point, so you may see Betula lutea in reference to this species. The name lutea refers to the yellow, or golden lustre to the bark of this species. Now "yellow" probably isn't the first thing that comes to mind when looking at this tree, but once you think to look for it, there is a bit of a dark golden tinge to the bark, interrupted by the pattern of thick, obvious lenticels - pores of the tree used for gas exchange.

Were you to actually scratch the thin layer of bark open, you'd pick up on a familiar somewhat sweet odor: Oil of Wintergreen. The odor will not be quite so strong however as it would be for the Sweet Birch (Betula lenta)

Sweet Birch (Betula lenta)

The Sweet Birch is a similar looking tree to that of the Yellow Birch, but lacks that golden coloration. The Oil of Wintergreen it produces serves as a flavoring agent in Birch Beer. I've never been a huge soda aficionado, so I had actually never tried this (well, or at least don't remember it) until a few years ago. It was OK. I had the Polar brand (Worcester's finest), so I'm not sure if that was the best direction to go. I'd say this tree is a little less ornamental than the other one's I've listed here, but has actually become rather important in New England ecologically speaking as it's starting to take over the forests traditionally inhabited by Eastern Hemlock, which are dying off due to the threat of Hemlock Wooly Adelgid.

River Birch (Betula nigra)

Finally, we have the River Birch, which can be readily identified by the reddish-tan colored bark, peeling off the plant with enough of a fervor to leave bare spots on the trunk. I'd say this is one of the more common birches cultivated in the landscape. For my friends in Boston, there's an aspiring grove of these about halfway down the Greenway (Somewhere between the Aquarium and the Intercontinental). They do put on a nice show in the fall when the leaves turn a brilliant yellow. I did find those trees a bit difficult to work with as I seemed to be constantly having to prune the lower branches, as well as water the trees heavily in the dead of summer, also proving difficult as the trees were planted on raised grass mounds which the water tended to roll off of. As the common name suggests, River Birches do like their water, and seeing the fall color show in mid-July can be a bit disconcerting.

Though I didn't explicit mention it throughout the article, I hope you're gaining a bit of an appreciation for some of the sight recognition tricks someone like me would use to quickly identify a birch tree while in the field. If I see a tree that I can identify as probably being a birch, to figure out which birch is a matter of asking myself a few questions: Is the bark peeling heavily? Do the twigs have a sweet soda-like smell when scratched? If so does the bark look golden? And if the bark is white, thin, and papery, how many male catkins does it display?

Next time you think you see a birch out in the woods try asking yourself the above and see what you come up with. Especially since you can't use the LeafSnap app since it's winter (though at 50 degrees again today I'm still not convinced).