Natural Sorrow

You could push your values more. I found a photo of actual poison ivy, and color picked the green values [link] . The light value is a bit lighter and more yellow than yours, and the dark value is much darker.
Then I took your image, and, since you weren't happy with the ruffles, I re-did the ruffles (trying to follow your painting as closely as possible) using the values from the poison ivy photograph. [link]
As you can see, the ruffles are more three-dimensional with stronger value differences.
I can't tell from the few images in your gallery whether you are placing the highlights through light logic (determining where the light is coming from and how it shades the object) or pillow shading (basically outlining shapes with highlights or shadows. Needless to say, using light logic will make for a more realistic picture, while pillow shading is more stylized and simpler to figure out. In any event, in each painting, you should decide which you want to use, and be consistent.