Champions targeting Zyra plants with abilities?

Was down to the last 4 and playing a Light composition when I came up against an Inferno/Summoner hybrid. Had been doing quite well against all the magic oriented comps because I had a level 3 Soraka with Sojin, rendering their teams mostly useless. However, every time I came up against this guy Soraka would cast her ability on Zyra's plants... on the edges of the arena... with no champions. This seems rather unfair considering you can't damage or silence them, so I'm hoping it's a bug? If it isn't then it should be. Completely invalidated my build, went from 78 hp and 1st place in the final four all the way to 0 with straight losses.