Whenever painting outside (and inside, too), I pre-mix my greens. It is kind of a security blanket for me. Using a limited palette, I create a super dark, top right, for accents, then three values, warm and cool of each. I use these as a reminder to stick to the three values and include temperature changes in both shadow and light sides. I use these as starter puddles and work off of them.
I didn't take a photo of the mixes for the azaleas, but used the same idea for the pinks and the whites. You can see how there are temperature changes in each value change of the azaleas.
It helps me to have a structure on my palette, otherwise I start mixing wildly and lose the value differences.
In the following photos, you can see how I started with the accent color first, putting down the darks, then went to the middle value, and at the end added the lights.
Massed in the big shapes, started adding some middle values.
Ready for final touches that will give it some twinkle, using the lightest values that are pre-mixed.