Start by strafing and shooting the spitting plants and vines. Once that's done,use your lychees on the seed pods. Next phase you need to shoot the petals till they droop down then grab on with your whip as prompted and yank them off. Make sure to stand a little back so you don't get hit on the head. Avoid the acid by rolling and destroy the vines that appear.
When the game says to cover yourself in goop, run back to one of the small blue and yellow flowers in the background and press Y to coat yourself in crap. Then run up the vine and jump into the flower to kill the boss.