Hydrangea macrophylla (hortensia) - A large leaves, deciduous shrub up to 6 feet tall that is ideally suited for shady areas and produces large, colorful flower clusters all summer long.  Generally, hortensias are divided into 2 groups.  lacecaps:  In this group, the inflorescences are composed of a showy ring of sterile flowers surrounding a not so showy mass of fertile flowers.  mopheads:  In this group, the entire (or nearly so) inflorescence is composed of showy, sterile flowers.  Zones 5 - 9.

Hydrangea macrophylla 'Nikko Blue' - A large, strong shrub to 6 feet with large, deep blue, globe shaped flower heads that are produced over most of the summer.

Hydrangea macrophylla 'Petite Soeur Therese de l'Enfant Jesus' (sister theresa hydrangea) - A healthy growing shrub with prolific amounts of fresh looking, cool white flowers.

Hydrangea macrophylla 'Pink Lacecap' - A very vigorous but compact shrub with numerous large, flat, pink, lacecap flower clusters over a long period.

Hydrangea macrophylla 'Tricolor' (variegated lacecap) - To 6 feet with superb foliage being a clear green variegated with greenish white and pale yellow plus having white inflorescences that turn a pale mauvish pink as they age.

Hydrangea quercifolia (oak leaf hydrangea) - A deciduous shrub to 8 feet with large, coarsely textured, lobed (5 to 7 lobes) leaves and large, showy, conical, white flower clusters.  zones 5 - 9.

Hydrangea serrata (tea of heaven) - A rapid growing, spreading, deciduous shrub to 6 feet tall with flower heads of the lacecap type that are either pink or blue depending on the soil pH.  Zones 6 - 9.

Hydrangea serrata 'Aigaku' [blue bird] - A charming plant of semi-dwarf to moderate size with blue, fertile flowers surrounded by a ring of light blue to purple, sterile flowers that are slightly fragrant.

Hydrangea serrata 'Blue Bird':  Please see Hydrangea serrata 'Aigaku'.