Visit any local nursery or garden center and you’re likely to encounter a confusing array of hydrangea species and cultivated varieties, or cultivars. We thought that it would be beneficial to have a brief discussion regarding the traits and identification characteristics of the most common types of these ubiquitous shrubs.

Let’s start with 6 species of hydrangeas that are common in western Pennsylvania. All are deciduous shrubs and are cultivated primarily for their ornamental features.

1. Smooth Hydrangea (Hydrangea arborescens)

Smooth Hydrangeas are a native hydrangea with gray-brown stems and thinner foliage and typically grow to about 3-6’ tall and wide in partial shade. Well-drained soils with medium moisture are necessary and they are very cold-hardy. Smooth Hydrangea blooms a little earlier than the other species and have white to pink mophead or flattened lacecap blooms that occur on the current season’s growth or new wood. Cultivars include ‘Annabelle’, ‘Incrediball’ series and ‘Invincibelle’ series.

2. Oakleaf Hydrangea (Hydrangea quercifolia)

Another native is the Oakleaf Hydrangea. This is a 6-8’ upright, rounded multistemmed shrub that spreads by suckering and will grow in full sun or partial shade with medium moisture. The leaves are thick, large, oak-like and dark green. The cinnamon-colored stems are exfoliating or have peeling bark. Oakleaf is the first hydrangea to bloom in early summer with large cone-shaped white flowers, born on old wood or growth from last season, that may turn shades of pink or red as they age. Noted cultivars are ‘Ruby Slippers’, ‘Alice’, ‘Munchkin’ and ‘Jetstream’.

3. Bigleaf Hydrangea (Hydrangea macrophylla)

Bigleaf Hydrangea usually grows to around 3-6’ tall and wide in partial to full shade with rich soils with medium moisture. It features elliptical, thick leaves and large, puffy, rounded mophead flowers or sometimes a lacecap-type flower in mid-summer on old wood. The flowers can be pink, blue or white depending on the cultivar and soil chemistry. This species includes many re-blooming cultivars or plants that produce flowers on old and new wood. Some cultivars are ‘Bloomstruck’, ‘All Summer Beauty’, Endless Summer’ and ‘Nikko Blue’.

4. Panicle Hydrangea (Hydrangea paniculata)

The latest bloomer is Panicle Hydrangea. This is a large, multi-stemmed shrub but may be trained as a small single trunk tree and is one of the most winter hardy species. It can be grown in full sun to partial shade and will thrive in urban gardens. The large cone-shaped flowers are usually white to green and turn shades of pink and red towards the fall. Flowers occur on new wood. Common cultivars include ‘Bobo’, Limelight’, ‘Quick Fire’ and ‘Pinky Winky’.

5. Mountain Hydrangea (Hydrangea serrata)

The Mountain Hydrangea blooms on old wood in mid-summer with pink or blue lacecap flowers. Foliage is similar to Bigleaf Hydrangea and the shrub is best grown in partial shade with medium soil moisture. Typical size is 2-4’ tall and wide and the available cultivars include numerous rebloomers such as the ‘Tuff-Stuff’ series and the Let’s Dance’ series.

6. Climbing Hydrangea (Hydrangea anomala subs. petiolaris)

As the name indicates, the Climbing Hydrangea is a woody vine that can climb upwards of 30-50’ if given the adequate support structure. It prefers medium soil moisture in partial or full shade and will produce fragrant white, flat-topped flower clusters from May to July.

The second article in this series discusses practical tips for growing and caring for hydrangeas.

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