Vegetation was the same until people started experimenting with it.
GENESIS 1:11-12
11 Then God said, “Let the land sprout with vegetation—every sort of seed-bearing plant, and trees that grow seed-bearing fruit. These seeds will then produce the kinds of plants and trees from which they came.” And that is what happened. 12 The land produced vegetation—all sorts of seed-bearing plants, and trees with seed-bearing fruit. Their seeds produced plants and trees of the same kind. And God saw that it was good.
JAMES 3:12
Does a fig tree produce olives, or a grapevine produce figs? No, and you can’t draw fresh water from a salty spring.
Vegetation changed when prompted by environmental changed just like everything else.