What is a plant?

For the record, my daughter is 3.

I made up a song with 2 parts. The first part teaches what makes a plant a plant, and the second teaches the 4 basic kinds of plants:

Plants have something green and they need the sun!
Something green and they need the sun!
Something green and they need the sun!
Plants are fun for everyone!

Plants have something green and they need the sun!
Something green and they need the sun!
Something green and they need the sun!
To do photosynthesis for everyone!

Moss, ferns,
Gymnosperms,
Flowering plants.
Moss, ferns,
Gymnosperms,
Flowering plants.

I found a couple pictures of different types of moss, etc., and I showed them to her as we sang the song. She loved it, and she picked it up really quickly.

Then we went on a plant hunt. We found lots of green things - grass, a leaf on the ground, a green puzzle piece - and we put them in a dark closet. We'll see what needed the sun, in addition to being green... She can't wait. She asks about it all the time, but we are waiting until the end of the week...

I intended for that to be it, but she wanted more. So...

We got a shovel and went outside. We dug underneath a wild flower and saw the root. I told her that the roots suck up the water and food from the soil. She thought that was really neat. We went and bought a flower at the local garden center. We watered it and put it by the window, because it needs the sun. Then, because she wanted to keep showing love to the flower, I told her it likes it when she talks to it. I told her about photosynthesis - how we give it Co2 and it uses that to turn the sunlight into sugar it needs and oxygen we can breath. She got it. People seriously underestimate the curiosity of a three year old.