The flowers are chalk pastel on water colour paper, which worked beautifully. The weight and texture of the paper really worked with the chalk pastels. I worked in pencil first from live flowers and then went in with the coloured chalk pastels. Real flowers are a good substitute for "life" drawing. You use the same skills but don't have to have a human model.
This one was three pieces of watercolour paper taped on a board together and I painted it as one image (with watercolours) and then separated them. I find this gives the work continuity. With the flowers I didn't need it so much, but with landscape I think it helps. A neat water colour lesson using this could be to assign the "three" paintings but have a different colour scheme in each panel. This would help the kids get used to the paints and using a variety of colours. It is easy to just stick to the paint colours that are within your comfort zone rather than experimenting with a wide variety of colours.
