In DragonVale, the opposite of the Plant element is the Cold element. This is due to the elemental interactions where Plant and Cold are considered to have contrasting properties. While Plant embodies growth and nature, Cold represents ice and frost, making them opposites in the game's elemental system.
A Plant dragon.
Breed plant and plant.
Water dragon.
Blazing+plant
Plant and Cold
Metal & Plant
Plant Dragon and Cold Dragon
To date, there is no grass dragon in DragonVale. You may be thinking of the plant dragon. See the related question.
Mine+ plant breed the evergreen and metal Forge+plant
You get a plant dragon.
$500
90% moss