Colourful celery

The little one wouldn't sleep yesterday morning, so we walked to our local supermarket as he fairly reliably snoozes in the pushchair.  We needed carrots, but little else.  Inevitably, we didn't just buy carrots... along with penguin ice lolly moulds(!) I also picked up some celery.  I never usually buy celery as I can't stand the taste, but it was inexpensive and I thought it would be good for three things. Firstly, the baby would probably like chewing on it; secondly to see if there is another green food the toddler might willingly eat (he likes peas and cucumber and barely notices spinach in things, and he tolerates broccoli, muttering "it makes me run faster and jump higher" as he eats it); and thirdly we could play with some food colouring in the name of science.

I decided to see if his enjoyment of coloured water would extend to seeing how the celery 'drinks' the water.  If you put celery in water with food colouring, the food colouring travels with the water up the xylem (little tubes) and so you can see them.  It's not instant and therefore he was likely to lose interest, so I decided we'd set it up before lunch, and then look at it after his nap.  We put one celery stem in some blue, another in some red, and a third in just water.

The celery set up with blue and red food colouring on the right

The little one and I had a sneaky look after an hour, and could see the blue had travelled all the way to the top of a 20cm-ish stem, so you could definitely leave it for less time.  If it had leaves on, I think it'd be quicker.

When he woke up, he was keen to look at the celery.  I took them out of the food colouring and showed him the tops, and asked him which one had been in the blue food colouring. He correctly told me it was the one with the blue dots.

I cut across the three stems a few cm below the top, and we had another look at them - the blue was clearly in the xylem (little tubes), and the red was faintly visible but a little disappointing.  I cut lengthways in the piece of celery that had been in the blue to reveal lengths of blue xylem so he could see blue lines, and we talked about how they were like little straws that the celery uses to drink (not quite a perfect analogy, but I thought it was close enough for a toddler).  He likes learning new words, so I told him they were called xylem, which is like xylophone in that it begins with an x, but sounds like it has a z.  He then told me that he didn't want to "do xylem" but wanted to "do colour science instead".  So we made purple with the remaining tubes of blue and red food colouring... three times!

If I was doing a similar activity to show how plants take up water again, I'd definitely use the blue colouring and maybe try a more concentrated solution of the red.  I might try doing it with some white flowers next time we've grown something suitable as he might find it more interesting.

Blue, red and uncoloured.  The blue nicely shows the xylem.
Blue xylem
I also wasn't successful with getting the boy to eat the celery (he tried it and said it was horrible and, as I agree, I could hardly persuade him otherwise), but his baby brother was very pleased with it, so at least I've found one good use for the remainder of the pack!