My reference photo is one I took at Tower Hill Botanic Garden in Boylston, MA, several summers ago. While I don't intend to replicate the scene exactly, I hope to evoke a sense of the place as I use this photo (and several others taken at the same time) as a basis for my landscape exercise.
Step 1 (above) My paper is a quarter-sheet of 140-lb. Kilimanjaro Original White, from Cheap Joe's (my go-to source for art supplies). I prefer 300 lb. paper, but I have a few more sheets of 140-lb. to use up and this seemed like a good opportunity. I began by covering the upper half with a pale, thin wash of Pthalo Blue, using a 2" Robert Simmons Skyflow brush, and after this dried I added shapes of green for the foliage (trees and low bushes, a suggestion of garden plantings, etc.) For these shapes, I used diluted washes of Green Gold, Undersea Green, Yellow Ochre, Shadow Green, and a very pale wash of Pthalo Blue (which can be too intense if used straight from the tube).
Rinsing my brush (a #12 pointed round) with each color change, I allowed the first splotches and puddles of colors to mingle on the paper. This produced some pleasing blends and soft edges (e.g. in the small clump of almost-white shrubs at far left). I dabbed in Burnt Sienna as a basis for some deeper-tone flowers, and then applied a thin wash of Green Gold and Pthalo Blue for the green lawn on the left. While this area was still damp, I added a bit of Shadow Green to the edge of the grass. I saved adding color to the distant curving path for later; the photo shows it as paving stone but I may change it to the type of brick-work on the path in the photo's foreground.
I continued to add shadows in the trees on the right, a few leafy details to the tree on the left, and more color variation in the largest evergreen in the middle. Alternating applications of pale washes of Mineral Violet, Burnt Sienna, and Pthalo Blue, I suggested banks of flowers –– again softening the edges by allowing the wet washes to mingle. In the foreground, I used stronger washes of those same three colors, and when these dried I added some leafy Green Gold and Permanent Sap Green details to suggest clumps of flowers. Mineral Violet combines beautifully with French Ultramarine and a wash of this along the garden edge of the path suggests a bit of a cast shadow.
Jo Ellen Reinhardt, our instructor (and founder of NESFA) suggested I look closely at what might be a problem area: a too-obvious diagonal that draws the viewer's eye from the lower right of the painting, to the left where it connects with the curving pathway. The task now is to find a solution.