To breed a seasonal dragon you have to in clued these tree elements:air,fire and plant
Never it's not limited
the only way is buy it with about 2000 gems
Some successfully reported parings are:Forge + PlantBlazing + LichenBlazing + PlantLava + AirPanlong + Evergreen
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.
There is no such thing as a Birthstone Dragon on DragonVale
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.
Blazing+plant
You don't breed a Kairos Dragon in DragonVale. You have to get parts to complete it.
To date, there is no grass dragon in DragonVale. You may be thinking of the plant dragon. See the related question.