The most common variety is the French Hydrangea. It is easy to grow in rich, moist soil, it has a large, mounding shape and can grow as tall as four feet in a year. The large foliage is dark green, but being deciduous, it is gone in the winter. Blooms appear on previous year's growth, so prune only the stems that produced this year's flowers; otherwise you will not have blooms next year.
The color of the bloom can be adjusted. White blooms will always be white, while the blue or pink can be controlled by the acidity of the soil (the more acidic, the brighter the flower). Add agricultural lime in the fall for a deeper pink color or aluminum sulfate for darker blues.
The Oakleaf Hydrangea is larger than the French, its flowers are cone-shaped and white, and the foliage turns a beautiful maroon in the fall. The unique tree form of hydrangeas called, Peegee, grows up to 15 feet and blooms late in the season.
Your local nursery can help you choose a hydrangea suitable for your location.