the only way is buy it with about 2000 gems
Sonic Dragon and Flower Dragon
To breed a seasonal dragon you have to in clued these tree elements:air,fire and plant
Never it's not limited
Some successfully reported parings are:Forge + PlantBlazing + LichenBlazing + PlantLava + AirPanlong + Evergreen
There is no such thing as a Birthstone Dragon on DragonVale
You will with get a Poison Dragon, a Flower dragon, a Seaweed Dragon, a Pollen dragon, a Willow dragon, a Fog dragon, a Blazing Dragon, a Rain dragon, a Swamp dragon, a Smoke dragon, a Rose dragon, a Seasonal dragon, or a Rainbow dragon.
Using the most common breeding combination, fire + willow, the probability is just under 13%.
Snow is added automatically with the DragonVale seasonal updates.
As of July 2012, there has not been a star dragon in DragonVale.
You don't breed a Kairos Dragon in DragonVale. You have to get parts to complete it.
Blazing+plant
To date, there is no grass dragon in DragonVale. You may be thinking of the plant dragon. See the related question.