Some people collect salt and pepper shakers, others small figurines or coins or stamps or antique cars or beer caps or . . . TWIGS! Yep, I would fall into the latter category and because I used them last week to teach a class, I thought I’d also share them with you.
If you stop reading right now, I understand. If you choose to continue, please know that some of what you read I’ve learned from the Maine Master Naturalist course, which first opened my eyes to twigs and buds; some from a variety of books on the subject; and lots from personal observation. You may not always agree with me, but I strongly encourage you to step outdoors and take a look. Keep track of your observations and begin to note idiosyncrasies. But do remember this: nature hasn’t read the books and doesn’t always follow the rules we’ve insisted upon as we try to make sense of the world around us.
Next year’s flower and leaf buds formed this past summer and overwinter inside bud scales, which are actually modified leaves. Most scales, such as this one, provide protection with a waxy coating. (Species: Norway Maple, Acer platanoides)
Terminal buds are located at the tips of most twigs. When that bud forms, the tree ceases to grow for the year. At the base of the terminal bud is a leaf scar where a former leaf stem was attached to the twig. And within the leaf scar are little corky dots called bundle scars that were actually the vascular tissue that had connected the leaf to the twig. Think veins. The shape of the leaf scar and number of bundle scars can be used as an identifying mark since they are often consistent across a species. (Species: White Ash, Fraximus americana)
Leaf scars come in a variety of shapes, including monkey faces topped with hairy caps. (Species: Butternut, Juglans cinera)
Others may be shield shaped, though you could also see a bit of a funny face in this one. (Species: Shagbark Hickory, Carya ovata)
And there are those that nearly encircle the bud. (Species: Staghorn Sumac, Rhus hirta)
Some twigs feature a false terminal bud. In reality, it was a lateral or side bud that took the position of the terminal bud. On twigs that don’t have actual terminal buds, such as American Elm and Basswood, the wood kept growing until the tree could no longer supply it with nutrients or something else impeded its growth. The twig then died back to the last terminal bud and dropped off. (Species: American Elm, Ulmus americana)
On those twigs with a false terminal bud, a branch scar was left behind when the woody structure broke off. The branch scar is located . . .
opposite the leaf scar, which contains bundle scars. (The branch scar does not have bundle scars.) (Species: American Basswood, Tilia americana)
Below the terminal or false terminal buds are lateral buds, those which grow on the side of the twig. Their orientation may be opposite, such as this example. (Species: Sugar Maple, Acer saccharum)
Others are alternate. The cool thing about this example is that the alternate buds are also appressed, meaning they grow flat to the twig; and they are one scaled (well, actually two scales fused together as one). (Species: Willow, Salix spp.)
Alternate appressed buds may grow far apart or quite close to each other such as with this particular tree and its globous buds. (Species: Quaking Aspen, Populus tremuloides)
Others are divergent and stick out away from their twig. (Species: American Beech, Fagus grandifolia)
Then there’s the pith. I just like saying that word–pith, pith, pith. Pith is the soft central core or interior of the twig. It comes in a variety of patterns including round, triangular and star-shaped such as is illustrated here. (Species: Quaking Aspen, Populus tremuloides)
In some species, its shape is best viewed in cross-section by halving the twig lengthwise with a sharp knife. Diaphragmed pith, solid with partitions, can be seen in Black Gum, which I didn’t find. But this example is chambered pith, which is hollow with partitions. (Species: Butternut, Juglans cinerea)
Another fun characteristic that aids in identification is the occurrence of catkins on members of the birch family. (Note: Betulaceae, the birch family, includes six genera of deciduous nut-bearing trees and shrubs: the birches, alders, hazels, hornbeams, hazel-hornbeam, and hop-hornbeams.) (Species: Speckled Alder, Alnus incana ssp.rugosa) Speckled Alder is really a shrub, but don’t tell it that.
Another fun thing to point out are the growth rings on twigs. We often think of aging a tree by counting the rings from the heartwood out to the bark, but . . . twigs have rings of their own. They’re a bit raised and wrinkled in presentation, but each cluster of rings indicates where that year’s leaf and flower buds had formed, developed, and released their seeds. After that, the twig continued to grow. The same will develop once the current buds complete their cycle. (Species: Striped Maple, Acer pensylvanicum)
If you’ve stuck with me, know that the end is in sight. I’d like to conclude this post with examples of some of my favorite trees found in the western Maine woods. I’ll begin with those deciduous trees with alternate buds. This particular twig is in a family that features catkins. It has several cousins so it’s worth getting to know a few of them. Notice the hairy twig, but not so hairy and rather pointed buds. Buds on older branches grow on stacked scars, which I’ll share an example of in a minute. If you were to squeeze these buds, they’d be sticky. Those are all great clues, and here’s one more. The tree’s bark is white and it curls away from the tree in rather big sheets.
Did you guess correctly?
Here’s a cousin and that example of stacked scars with the bud at the end that I promised. Notice the lack of hair? The clues for this species: scrape the bark on the twig and sniff it. Does it smell like wintergreen? And the bark on the trunk–does it peel away like ribbons? (Species: Yellow Birch, Betula alleghaniensis)
And another member of the Betula family. This one is an early succession tree, meaning it grows quickly in fields and along roads that have been disturbed. But it is also the shortest lived of the family and doesn’t reach an old age in tree years (Yellow Birch can grow to be about 250 years and Paper Birch about 150). This species is lucky if it reaches its 90th birthday. Though you can’t see it here, the twig isn’t hairy, but it is quite bumpy or warty. And it doesn’t have a wintergreen odor if scratched. Also, the bud isn’t sticky. Though only one catkin is shown here, it could have two, while Paper Birch has three and Yellow three or four. Who is this?
I’m sure you guessed it.
Another of alternate twig and bud orientation, this particular bud is often described as a cigar. I’m not sure that works for me–maybe as it expands a bit in the spring, but the multiple overlapping scales and pointed tip make it seem obvious as its different from all other presentations. Plus, its leaves are marcescent, meaning they wither or remain on many younger trees throughout the winter. Actually, it’s easy to be fooled into thinking a mammal is moving nearby for in a slight breeze the marcescent leaves rattle. I’ll admit I’ve jumped a few times. Back to the buds–the other thing to note is that like a New York Fern, it tapers at both ends (maybe they, too, keep their lights on at both ends of the day). Who is this?
Bingo! You are on a roll! I should define lenticel at this point. Those raised white dots on the twig are the lenticels, which are the pores that provide openings for air-gas exchange.
We haven’t talked about the fact that some twigs have buds crowded at the tip. In this particular case, I think of them as a crown.
This cousin also wears a crown. So, what are their differences? The first is more conical and shinier than the second. And look at their colors. Number 1 comes in shades of chestnut brown, while number 2 is much darker and almost reddish brown in tone. You’d have to look carefully to see the silky hairs at the pointed tip of number 1, but trust me that they are there. Number 2 is hairless and blunt.
This is number 1. Did you guess that correctly? And number 2 is . . . White Oak, Quercus alba.
Now it’s on to trees with opposite orientation. And if you think you’re seeing double, you are! I used this photograph at the start. But now, let’s compare this twig to that of a cousin.
Can you see the fuzz on this one? And no fuzz on the one above? Also, notice in the first one the notched leaf scar. The second is not deeply notched. Who are they?
Two of the three ashes that grow locally. Identifying White and Green Ash, as they are respectively, is never easy, but the hairs or lack of, and the shape of the leaf scars are the key elements.
And finally, two members of probably everyone’s favorite fall trees. Notice the lateral buds are arranged on opposite sides. The buds and branch are purplish brown. On the twig, the buff colored lenticels practically jump out. The bud is a tad bit hairy and sharp pointed. Do you see the leaf scar bundles? How many? I hope you counted three. And who might this be?
You are almost done. Only one last twig to examine.
This one is probably Maine’s signature tree when it comes to fall foliage. And of all the members of the Maple family, this is the most abundant species. So, remember the crowded buds on the Oaks? Well, this twig also sometimes wears a crown. But, the terminal bud is wedged between two opposite lateral buds. And the color–red, because there’s always something red on this tree. Hint. Hint. If that didn’t give it away, this will . . .
I love Red Maple. If you haven’t done so, follow the progression of its buds and I hope you’ll be wowed when it flowers next spring. Until I looked, I never noticed its dainty flowers. Now, I can’t not look.
If you’ve stayed with me thus far, congratulations. You deserve an award. Or at least a hearty THANK YOU!
There’s more, but I’ll let the bigwigs handle that. I just learned of a new book about trees that I plan to purchase soon entitled Woody Plants of the Northern Forest: A Photographic Guide by Jerry Jenkins. Thanks to fellow naturalist Anita Smith for the recommendation. I can’t wait to add it to my bookshelf.
Who knew there could be so many idiosyncrasies? After all, aren’t they all just twigs and buds? Ah, the wonder.
I hope you’ll refer to this primer periodically as you gain a better understanding of twig morphology. And share it with your friends 😉