Yes just choose ashenvale instead of summer.
If you do use another flamestrike, which I do not recommend, make sure one unit does not have both spells. If one unit has two spells based off the same spell casting one will often cast the other. I have been having alot of trouble with this recently in one of my maps.
Also if you want the regrow radius the same as the flamestrike radius change one. You do not have to use 256. Look into the spell, find the AoE that you set, or is defaultly set, and change the trigger number to that number.
Also I havent really tested this. It should work though so try it out and tell me how it goes.