I'm sure there has been worse art in the Alpha timeline.

It might be possible to reduce the lineart contrast between the leaves and trunk by using the magic wand tool (on GIMP) very specifically on the outline for the leaves, and then replacing the color with a darker shade of purple.

Can you add a little more detail?

I mean, it's already more descriptive than its ancestor's, which was just a few gens ago.

You shouldn't feel concerned about your art, it's still way better than mine.

What defenses does this have against herbivores, beyond its size? Presumably boring minikruggs and sapshrooms might be a mild threat to these.

It doesn't have much defense, apart from size and speed of reproduction.