It’s that time of year when buds are starting to break their winter dormancy. In December 2014, Daniel and I went for a walk through the Carolinian Forest at UBC Botanical Garden to investigate and photograph buds. We found lots of them! I’ve chosen a few of the photos we’ve taken to highlight some interesting facts about buds.
Today we feature a comparison of two types of mixed buds: the large, scaly brown buds of Aesculus glabra, or Ohio buckeye, and the long, smooth light brown (and looking orange against the blue sky) buds of Fagus grandifolia, or American beech.
A bud can be thought of as a condensed shoot, from which embryonic leaves and flowers arise. At the centre of the bud, on the end of the bud’s short stem, sits a growing point. The growing point is surrounded by an inner layer of leaves, densely folded and crinkled to fit a large surface area into an incredibly small space. In temperate shrubs and trees, the outermost layer of the bud is often composed of thick, tough leaves that form the protective scales (or cataphylls) that we can see in the photographs. These scales come in all sorts of shapes, sizes, colours and textures, from the satiny smooth American beech buds to the rough, sticky scales of Ohio buckeye.
There are many ways to categorize buds. Both buds featured today are scaly, as opposed to naked or hairy. They are also both resting, which means that they formed at the end of the growing season, and will resume growth soon this spring. Another commonality between the Aesculus glabra and Fagus grandifolia buds shown is that they are both mixed buds, meaning they protect both developing leaves and reproductive parts. One final way to describe buds relates to where the bud is formed. Both photos show a terminal bud located at the tip of the stem, and one or more axillary buds located at the axis of a leaf. Sometimes, buds form in other places; these are called adventitious buds, and can be found on roots, at the inter-nodes of the stem, on callus tissue at the cut end of a stem or root, or on the edge of a leaf blade.
Once the growing season resumes, the stems within the buds will begin to elongate and grow. Terminal buds will continue to lengthen the shoot, while axillary buds will form new branches. It is possible to use the scars left behind by terminal buds to age a shrub or tree. Each growing season is represented by a terminal bud scar, which looks like a series of narrow grooves around the twig.
This is also a good time to point out the little, light-coloured bumps found on the stems of both the American beech and Ohio buckeye. These bumps are termed lenticels, and are small openings in the stem’s bark that allow oxygen and carbon dioxide to pass in and out of the stem. Like scales, lenticels can also take on different forms; the horizontal “stripes” found on cherry trees is an example of lenticels that looks quite different from those shown today.
For even more information about buds, visit the buds entry on the Ohio Plants website, where side by side images explain many of the concepts discussed above.
Ah, a species near and dear to my heart as a an Ohio State Alumnus that studied botany then natural resources. It was a very interesting entry today.
In my opinion, buckeyes and Old World horse chestnuts have some of the most beautiful emergent foliage this side of Acer (which I believe they are more closely allied to that oaks and chestnuts which their genus name and the common epithets of the later allude to).
One story that some here might find amusing is that, when the football teams for the University of Oregon and the Ohio State University were getting ready to play for the national title a few years ago, my brother brought my attention to a story about the 1958 Rose Bowl and a bet between the respective university presidents. The result was that a buckeye tree was sent to Eugene, Oregon and planted on the University of Oregon campus, where it grows today. The funny part is that the Ohio State administration sent the wrong species, Asculus flava (also an Ohio native but definitely not the right species).
https://around.uoregon.edu/content/uos-buckeye-tree-commemorated-55-years-after-fact-video
great choice…not long to go till it’s officially spring! Here in northwestern Connecticut a few Daphne mezereum ‘Alba’ buds are showing white and the maple sap started to run a week ago (2nd earliest in more than 70 years).
While not a student of botany this article made me go take a look at my Osage orange tree and my Red maple. Neither is active yet. Therefore to small to photograph. 🙂 Our Huisache trees are now blooming in the area, the scent is heavenly.
Interesting description of bud characteristics, and helpful … thanks
Daniel, these photos are amazing, and well-timed as I am just this week and next teaching a winter plant ID class that, among other things, discusses buds and the categorizations you mentioned.
I am wondering if I am in error: are these buds truly vegetative? Aren’t they reproductive? Both of these species bloom in spring and, though only dissection would tell for sure, I would assume most of their large terminal buds like these actually contain both flowers and leaves. What do you think? If I’ve been teaching the wrong thing, I’d sure love to know before my class next week!
Thanks as always for showing us this beautiful world. I’ve been a reader for six years and counting, I think.
This was an entry photographed and written by Tamara some time ago, before the site went down for a while.
I would think that in both of these instances, the buds contain both nascent vegetative and reproductive parts. I will change the terminology to “mixed buds” (thank you for the correction!).
Ah, I missed the byline. Thanks for the correction, and the reminder of “mixed buds”
Timely, well written and instructive, thank you!