In it I used gouache in the center of the flower. (The off white and yellow is gouache and the pink is watercolors.) Gouache is an opaque watercolor. Watercolors are more transparent. The gouache allows you to "cover up" more easily.
Traditionally when painting in watercolors you do not use gouache. Especially to paint the whites. You leave the paper to show the whites. I do not use gouache in my watercolor painting as I love the transparency of the watercolors. But sometimes I use it to capture a more opaque area like the center of this flower. I also use it to add a little white as in my Central Park and Ocean Wave paintings. This is why I think of it as mixed media.
Some people use gouache with their watercolors. They mix it with the colors and paint beautiful opaque paintings. Gouache can be mixed with watercolor colors and or the different colors of gouache can be mixed together. Some people paint with gouache alone.
There are three nature books by Maryjo Koch that you should check out. They are Seed Leaf Flower Fruit, Bird Egg Feather Nest and Pond, Lake River Sea. Her paintings are beautiful and she uses gouache.