It always begins with observation. I spend time with elementary art students, talking about the difference between looking and seeing. We used a viewer to isolate one area of the plant. This keeps people from being overwhelmed by the whole object. It also enhances opportunities for detail, and a fresh view.
After drawing with a pencil the lines are gone over with crayon pastel. This adds more interest and control when water colors are introduced.
A black outline (dark blue works well too) is added before the background is filled in. This adds a cushion and keeps students from brushing over outlines.
Below are some samples of student work
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