I bet you didn't know that you can figure out how old twigs are too, and you don't even have to cut them down to tell. Twigs have so much to say once you know how to read them. This post is best if you have a twig and a magnifying lens nearby, but in case you don't, I've included some fabulous drawings to help you. I hired a professional artist and spared no expense. Twig details are usually too small to photograph well, unless you have a buckeye twig which are out-sized and easy to see. I haven't found a buckeye in Chicago yet, so you'll have to make do with these drawings instead of photographs. All the parts I'll discuss here are visible on all twigs, but most are a little smaller.
|Artist's rendering of a buckeye twig on archival-quality notebook paper.|
|Buds - terminal and axillary|
|Bud scales, bud scale scars and leaf scars.|
Twigs also have tiny dots on them called lenticels. If you zoomed in on a lenticel, you would see an opening with a tiny mouth-like structure that can actually open and close. The opening is called a stoma, and it is for allowing exchange of oxygen and carbon dioxide into the air - basically it allows the plant to breathe. You have probably heard of stomata (plural of stoma) on leaves before, and these are the same thing, just on bark instead.
|Lenticels and age of twig|
Deer like to eat terminal buds off of edible trees because of the tender, living material inside. When that happens, axillary buds are activated, and often several side-branches will grow during the next summer. This can give a branch a bushy appearance. When you trim a branch by chopping off the end of it, the same thing happens. Whatever grows back will be bushier. If you trim off an entire side branch where it joins a larger branch, the next year's growth will not be bushier - instead the terminal bud elongates and the branch just gets longer. You can influence the shape your trees and bushes by trimming off side branches completely to encourage them to grow in the direction of the remaining terminal buds.
|Twig life history|