I love the detailed plants, the excellent pose, and the flow of the hair. This illustration of Poison Ivy definitely gives off a strong sense of power. I really like how there's a vine coming up between the pinky and fourth finger of her left hand--it really gives the sense that she just doesn't care of is one with the plants.
She's sexy, cool, and dangerous. I think that's why I like her as a character. I also like your pic here! It's awesome. X3 The ample green gets me, and the bright reds are a great contrast. I also think the hands rock. Very excellent work, croaky.