The Science of Gardening Part 1: Monocots vs Dicots
Ask Science looks at the difference between two types of flowering plants: monocots and dicots.
This week, I kick off a new series on the science of gardening with a look at the difference between two types of flowering plants: monocots and dicots.
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Monocot vs. Dicot
As I’ve mentioned before, scientists loved to classify things. Whether it’s a bison, buffalo, or something in between, some scientists just can’t seem to get enough of arranging things into phylogenies. So of course, they’ve come up with all kinds of exciting ways to classify the angiosperms of the plant kingdom, more commonly referred to as “flowering plants.“
The two main groups of angiosperms are the monocots and dicots. Dicots are sometimes referred to as eudicot, which sounds a lot like “you da cat,” but which actually means “true dicots”–so we’ll just stick with “dicot,” for reasons that will hopefully make sense soon.
The “cot” in monocot and dicot is short for cotyledon, which is Greek for “seed leaf.” It refers to the first leaf to emerge from a germinated seed. As you might have already inferred from their names, monocots have one seed leaf, while dicots have two.
If you’ve ever had a child bring home a little cup of dirt with a bean seed planted in it, and watched two little leaves poke up out of the soil, those are the ones we’re talking about here.
In the Field
Now, if you’re watching a plant poke up out of the ground for the first time, it’s pretty easy to tell if it is a monocot or dicot. But what about one that you see growing in your yard? Well, it turns out that is pretty easy to figure out, as well.
The first thing you can look at are the leaves. Monocot leaves tend to have parallel lines that run the length of the leaf. Dicots, on the other hand, will have a web of lines crisscrossing willy nilly all over the leaf, that tend to come from a central rib.
Another tell-tale sign is the root system. If you pull a monocot up by the roots, you’ll see a stringy mess of crisscrossing roots. Dicots, on the other hand, tend to have a large, central tap-root, with smaller roots branching off of it. If you’ve ever tried to pull up a dandelion and saw the long, thick root in the center, that is a typical characteristic of dicots.
The final easy way to tell the difference between monocots and dicots is by their flowers. Monocot flowers tend to have petals in multiples of three. Their sepals (the part that wraps around the petals before the blossom opens) sometimes are the same color as the petals, so you’ll see three petals and three sepals that are the same color. Dicots, meanwhile, typically have petals and sepals in multiples of five or six.
So, Why Do I Care?
So, Why Do I Care?Now, unless you’re a botanist (or a gardener that just has a strange desire to classify their plants,) you might be wondering why you would care about this? There are a couple of reasons why the average gardener might want to know if a plant they are looking at is a monocot or a dicot.
The first reason is that some herbicides will only kill monocots, others will only kill dicots, and some will kill both. So if you’re spraying your yard to get rid of dandelions, you’ll want an herbicide that kills dicots, because grass is a monocot–and you probably don’t want to kill the grass in your yard.
On the other hand, if you’re spraying your garden area to kill grass, you might want an herbicide that kills only monocots, so that any stray grass will die, but your dicot beans will still live. However, you wouldn’t want to do that if you’re growing corn, because corn is a monocot. So if you’ve got both monocots and dicots in your garden, you’re just going to have to pull the weeds by hand, which is probably better for your health anyway.
Another reason you might want to know the difference is that most monocots (grass being a notable exception) don’t do well if you cut the tops off. If you’ve ever seen people cut the tops off trees to curb their growth, know that this will only work on dicots. If you try this on a palm tree (which is a monocot,) it will most likely just die.
Conclusion
ConclusionSo now you know more about dicots, monocots, and, hopefully, why that information is helpful to the average gardener.
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Photo of gardener spraying courtsey of Shutterstock.
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About the Author
Dr. Lee Falin earned a B.S. in Computer Science from the University of Illinois, then went on to obtain a Ph.D. in Genetics, Bioinformatics, and Computational Biology from Virginia Tech.
