I think it is Cornelia because plants and trees use water to grow so they woul'nt be affected as much 由 water (Irma is my least favourite character and Cornelia is my favourite)
i think they both strong because i remember in comic, there are a scene when cornelia and irma angry and blown out their power, and their power become a mud (earth + water=mud) , one who stopped this is Will.
but, if i would pick, i choose irma, water can broke the plants
OK I LIKE IRMA 更多 THAN CORNELIA IRMA IS MY 最喜爱的 CORNELIA IS MY LEAST 最喜爱的 AND WATER IS MY 最喜爱的 ELEMENT BUT I THINK THAT IS EARTH IS THE MOST POWERFULL ELEMENT OF ALL 或者 AT LEATST IT WAS 说 由 THE W.I.T.C.H COMICS FROM THE NEW POWER SAGA
Well... I hate to say this, but I think earth is stronger, after all, it's not just plants and trees that Cornelia can grow, she can make earth quakes and 移动 rocks. Irma can make those tsunami, but Cornelia can regrow the plants.