Cryofreeze

You cast a beam of negative toward a single creature. Freezing the particles of water inside its body. This creature makes a constitution saving throw. It sees its AC be downgraded by 3 points for the duration of the spell and take 1d8 points of cold damage on a failed save, or half as much damage on a successful one

non-biological creatures are immune to this spell

if this spell is cast on a non magical plant, it simply freezes and dies