Collecting Leaves and Dichotomous Keys

by Deb on February 19, 2010

Little ones will love the collecting leaves bit, but expect them to lose interest very early in the keys.  It’s still a great activity for them because it gets them to really look at things closely and is very language rich. Dichotomous keys are a very useful classifying tool to know, plus I love the name – say it out loud, die-KOT-o-mous key.

My girls race all over the yard getting leaves then comparing them.  The idea of a dichotomous key is to use a rule to split things into two groups, then keep splitting the groups until you only have one thing in it.  You end up with a good description, and later if you use the right rules it can help you learn about relationships between plants, or how rocks have formed, or what reactions a chemical is likely to make.

Right click on the picture and open it in a new window to be able to see the one we made of leaves.  Big girl got the idea pretty easily, but lost interest after a few splits.

  • For babies you are aiming to get them to play with different leaves, especially feeling them – be very careful what they are!
  • For older babies you can introduce lots of nice descriptive words – long, short, rough, smooth, soft, big, small.
  • Toddlers should be able to sort into groups, for example the first split on this key is into ‘Round’ and ‘Long’ groups and big girl sorted them for herself.
  • Pre-schoolers can start to work out their own rules for splitting.  This is harder than it sounds – it’s quite an abstract idea to make up a rule and then apply it, especially if it has to be something that will work for all the things in the group.  The big girl managed to come up with several on her own – things like long/round, furry/smooth and she noticed the veins were different between the grass and other leaves.

Older kids can do a full dichotomous key.  You can see here the groups don’t have to be balanced, but the idea is to keep splitting into two.  The grass stems are quite different to other leaves, they can be described quickly as long with veins that run along the leaves.  The mulberry leaf, on the other hand, is round, smooth, soft with pointy edges and came from a tree or the basil is round, smooth, soft with smooth edges and smells.

  • A big sheet of paper you can write on and sort the leaves on top of makes it easy to remember what your rule is.
  • You can use the same rule with different groups – we used the ‘furry/smooth’ rule twice.
  • You can use a dichotomous key to sort absolutely anything – rocks, soft toys, TV shows, people in a family, … Learning to discover and apply a rule is an extremely useful skill.
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{ 6 comments… read them below or add one }

@ConfidentWoman February 19, 2010 at 4:26 pm

Fabulous I have always loved leaves since my father showed me them as a kid, so good to introduce children to your science


Kristine February 19, 2010 at 5:16 pm

I did this once with 10 -12 year olds using shells. We thought it would be easy for them but even just generating their own categories (which were ‘opposite’ in nature) was new to them.

I have a surprise for you


miss carly February 19, 2010 at 9:34 pm

Oh my, this is fantastic! There are a number of different items you could do this with! Including buttons, shells, fabric cut-offs, paper and coins.

Lovely! I might have to use this whilst out on prac if i get the chance!


Amber February 20, 2010 at 2:07 pm

Thank you for putting this concept into a way I can do it with my 3 year old. I think she will love this “game” I’m interested to see the rules she comes up with! We might start with toys because there aren’t a whole lot of leaves around our house just now.


Annie February 23, 2010 at 6:03 am

Oh this sounds like a great activity – as you say with any objects we can find. My 3yo in particular loves sorting things and already comes up with really detailed descriptions of things, like ‘all the people who are boys and are wearing shoes’… So this would be a great way to help him develop that skill


Deb February 24, 2010 at 10:00 am

Absolutely. I love the idea of buttons, because I’m a sewer. And we are going to do the soft toys on the next rainy day!


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