hydrangeas (Hydrangea) — identification, habitat & look-alikes

Hydrangeas are a group of flowering plants that mostly grow as shrubs. In the United States, the group includes native woodland shrubs such as smooth and oakleaf hydrangeas as well as widely planted Asian garden species. The showiest parts of many hydrangea flower heads are enlarged , the leaflike parts outside the petals.

In this group

bigleaf hydrangeaHydrangea macrophylla

A common garden species with mophead or lacecap flower clusters. Cultivars may have blue, pink, purple, or white showy sepals.

smooth hydrangeaHydrangea arborescens

This shrub is native to north-central and eastern parts of the United States. Cultivated forms are widely known for broad white flower clusters.

oakleaf hydrangeaHydrangea quercifolia

This southeastern U.S. native has deeply lobed, oak-like leaves and cone-shaped white flower clusters. Older stems develop peeling reddish-brown bark.

panicle hydrangeaHydrangea paniculata

Large cone-shaped clusters separate it from round mophead forms. It is an Asian species widely grown in American landscapes.

Appearance

Growth form: Most are shrubs that lose their leaves in fall, but the genus also includes small trees and climbing vines.
Flowers: Flower heads may be flat, ball-shaped, or cone-shaped. Bigleaf hydrangea cultivars are especially well known for blue, pink, purple, or white sepals.
Fruit: In many species, fertile flowers can produce small fruits with tiny seeds. Garden varieties dominated by may set little or no seed.
How to recognize it: Leaves are usually opposite and toothed. Many species form broad flower clusters with small fertile flowers and larger sterile florets around the edge, although cluster shape varies widely.

Look-alikes

Japanese snowball viburnumViburnum plicatum

Japanese snowball viburnum has distinctly pleated leaves and blooms in spring. Bigleaf hydrangea has broader, smoother leaves and usually blooms in summer.

Why they get mixed upBoth can be shrubs with large round clusters of showy sterile flowers.

Where it lives

Typical habitats: wooded slopes
streambanks and ravines
gardens and parks
Range: Hydrangeas are native across parts of Asia and the Americas. In the United States, smooth hydrangea (Hydrangea arborescens) is native across much of the East, while oakleaf hydrangea (Hydrangea quercifolia) is native to the Southeast; several Asian species are common garden plants.
Preferred conditions: Many grow best in moist, well-drained soil with some shade, but how much sun and cold they can withstand varies by species and garden variety.

Growing it

Propagation: Garden hydrangeas are often propagated by stem cuttings or . Species can also reproduce from seed.
Toxicity: Poisoning has been reported after people ate bigleaf hydrangea (Hydrangea macrophylla). Do not treat ornamental hydrangeas as food.

Name and classification

Group name: In everyday American English, “hydrangea” can mean the whole genus or the familiar garden species bigleaf hydrangea and its varieties.
Varieties and forms: Garden forms include lacecaps, with a ring of showy sterile florets around small fertile flowers, and mopheads, with a rounded mass of showy florets. These forms are especially common in bigleaf and mountain hydrangea cultivars.

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