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Pressed Plants

Pressed Plants
Some of the many pressed plant samples in the herbarium

Remember being a kid and pressing flowers in between the pages of a book? Well it turns out that you can make a career out of that! In order to have a record of all of the different plant species, scientists take pressed plant samples of each species they collect and put them all together into something called an herbarium. There’s a really cool herbarium at The Morton Arboretum that has everything from flowers, to lichens, to trees in its collection.

 

A photo of just a few of the many shelves of stored samples in the herbarium
This is only a very small snapshot of the lichen collection at the herbarium. There are thousands of samples neatly stored in dozens of cabinets

I was up in the herbarium looking through samples of shinnery oak, which is the species I’m focusing on this summer. It’s really helpful to have these collections to look through, because the shinnery oak doesn’t grow up here in the midwest - it’s native to the deserts of the American southwest. One thing I found to be really interesting is how different individual plants can look even if they are of the same species. It does make sense though, when you think about it: we're all the same species - human - but we all look very different from each other (like how we all have different heights, eye colors, and fingerprints). In the exact same way, plants of the same species differ from each other too. It was really neat to see how much variation exists between different oak individuals!

 

Two different samples of the same species that look very different - one with large leaves and one with very small
Two individuals of the same species can look very different. Here are two oaks of the same species - one with large, lobed leaves and the other with small, unlobed leaves

Once plants are dried and pressed, they are well preserved and can last a long time. As I was flipping through the oak samples, I was making note of the collection dates. Most were from the 60’s, so the samples were basically my parents’ age, which I thought was pretty cool. Until I got to a sample from 1916. So this little dried and pressed branch that I was holding in my hand was 100 years old?! I think it’s incredible that just pressing a plant can preserve it so well for so long. There is a lot of history sitting up on the third floor of The Morton Arboretum!

The label showing that this sample was collected in 1916
This is the handwritten label showing the collection of the shinnery oak from 1916