Conifers. Oh, my goodness, who doesn’t love conifers? As in wonderful smells, pinecones, Christmas trees, snowy days, and fun trips to the mountains. I grew up in southern California and the conifer that I loved as a child was the ponderosa pine. It had bark that pulled apart into jigsaw shaped pieces. The bark smelled like butterscotch (or maybe vanilla), and the long needles grew in little bundles of three… perfect for braiding!! The cones are perfect for dabbing with white paint, sprinkling with glitter, and then using for holiday decorating. Perfect tree, the ponderosa pine. It is beautiful and kind of feathery with clumps of needles near the ends of branches.
Then I moved to Colorado.
Oh, boy, did I need to learn a lot more about these trees. There are a lot of conifers in Colorado, and they grow in different environments and elevations as you drive up into our mountains. The ponderosa pines are found at lower elevations (5,000 – 7,000 feet) and then as you drive up into higher elevations different trees start to show up as the ponderosas disappear. In high elevations they are nowhere to be found, and the trees that are around 10,000 feet are specialized and designed to live in challenging environments. One tree has branches that are so flexible you can tie them in knots (limber pine), and another is just dripping in anti-freeze sap (bristlecone pine).
One summer I took a forestry class and spent a couple of weeks coring trees and recording their elevation and growth into a large data base maintained by the U.S. Forest Service. I learned to shield my coring activity from casual hikers (Yeah. People in the Boulder, Colorado might take extreme exception to your activities if they suspect that you are harming a tree… tree huggers are alive and well here!) and developed an appreciation for the impact of local environmental conditions on trees.
As a biology teacher I struggled to teach plants (yawn) and taxonomy (super-yawn) to my students. I searched for hands-on activities that could be used to teach these units, and finally remembered that the teachers in the high school where I did my student teaching ran a big lab where students used keys to identify Colorado’s conifers. Another teacher had keys that we could adapt to use with the activity and off I went on a road trip to collect conifer samples in the Rocky Mountains west of the town where I live.
Why use conifers? Well, they are pretty darn interesting if you think about it. The plants produce two different types of cones (seed, on the left, and pollen, on the right) and have leaves that are needle like. They are older than flowering plants in evolutionary terms and have some cool adaptations. They use wind to reproduce and have turpentine and other organic compounds that allow them to stay alive in cold climates. Cut branches are hardy enough to survive handling by hundreds of students as they worked the activity. Yeah. Conifers were the ticket!!
So, how did this work? The students picked up bins with samples of branches and cones from the plants and, using the keys, figured out what conifer they had. The key took the students through a decision tree using needle and cone characteristics that became more and more detailed as they moved down the decision tree.
For instance, were needles single or in clusters? Were they round or flat? Were they sharp or soft to the touch? (Left to right, these three are the blue spruce, the bristlecone pine, and the white fir. Spruce needles are round and sharp, pine needles grow in clusters, and firs are flat needled and soft to the touch.)
Differences in cones can be extremely helpful in identifying the species. Left is the seed cone from a Douglas-Fir and to the right the seed cone from an Engelmann spruce.
I bet you can see it without me saying anything. Conifers that are closely related have very similar characteristics; closely related species are very difficult to tell apart and the differences are subtle. In the real world the final sorting is sometimes done by differences in DNA. It was easy after this activity to move into the more abstract topics of classification (Kingdom, Phylum, Class, Order, Family, Genus, Species) and then link back to evolution with the tree observations: some closely related species actually grow at different elevations on the mountain. Living in different environments, these trees don’t reproduce with each other and have gradually grown apart into different species.
I struggled to key out conifer samples as a new biology teacher. Nowadays I can identify the tree while driving by on the road and I didn’t bother to drive up into the mountains anymore at the end of my teaching days. I would just pull the car over and clip off a little branch and grab some cones if I could: gone in 60 seconds was my motto! There are some great trees in my local park and the high school where I used to teach had 5 different Colorado conifers on the property. I have a Douglas-Fir in my back yard. I can get at least 11 different conifer samples in a one-hour drive around town. I haven’t taught this activity in years and yet I still look for great trees while out on errands.
Because conifers make me happy!!
After all, who doesn’t love conifers?
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