Right now i'm trying to craft the fire mount so I was wondering if you can get ultra helephant ears from harvesting regular helephant ears?
Yes, they drop them and this is a great way to get Deadly Helephant Ears (from the ultras) for the mega snacks as well. A lot of players will plant the Ultras, harvest them once -- they elder fast, wilt them, revive them, and repeat to get the DHEs.
Overall the drop rate for ultras is about 1 in every 35 plants. Sometimes more, sometimes less.