Cactus Sponge Experiment

I knew cactus could store a lot of water, but I had no idea how much!  Did you know that a fully-grown saguaro cactus can soak up and store up to 200 gallons of water during a good downpour? And then they can store the water until the next rainfall (which in the desert might be awhile).

I wanted to demonstrate this concept with Ava.


First, I started by cutting sponges into the shape of a cactus.  Then we put a little bit of water into two cups (one for her and one for me). I asked her what she thought would happen when we put the sponges in.  Ava says “wet!”  She was mostly right.


We put the sponges in the water and at first, the sponges only got their “feet” wet.

We got to watch the water slowly crawl up the cactus, but it only got about half of the way up right away.


We tried waiting a little bit longer, but it wasn’t moving fast enough (at least not for the toddler’s attention span), so we left them out on the counter overnight.

In the morning, the WHOLE cactus was wet!  And the sponge stayed wet almost another day.  Ava was mildly impressed… but I thought it was super cool!  I think if we do this again when she’s older, she would appreciate it more.  She really liked the first part (where you could watch the water climb up the sponge) but I don’t think she appreciated the fact that the sponge had absorbed everything by morning.  To be fair, she is only two.  I still loved it and would do it again, especially because it was so easy.  We may use the sponges to do cactus painting later too – Ava loves painting.

See more about our All About Cactus Week here!

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