Plant of the Month for August, 2014

Cephalanthus occidentalis header
Cephalanthus occidentalis

 (sef-uh-LAN-thus ok-sih-den-TAY-liss)

General Information:

Cephalanthus occidentalis, the buttonbush, is a very interesting shrub that is rarely seen in gardens. It’s flowers are so unique that it always attracts attention when in flower. Even the seed heads make a statement in the garden.

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 Cephalanthus occidentalis; photo by Robert Pavlis

The buttonbush is native to most of North America and Mexico and is found in wet swampy areas. It’s fondness for water is one reason it is not found in many gardens, but it is an ideal plant for a wet location, bog garden or a rain garden.

The flowers are white and almost the size of  a ping pong ball. Each flower lasts about a week, but they are produced in succession. The left picture below shows the current flower as well as several developing buds. The flower head is actually made up of many small individual flowers, shown in the right photo, which together form a ball, much like an Allium flower. Long projecting styles stick out past the petals giving the ball a starburst appearance.

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Cephalanthus occidentalis; photo by Robert Pavlis 


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Individual flowers, photo by University of Texas

Individual flowers photo was kindly provided by Plant Resources Center and Bio406d at the University of Texas at Austin.

The flower is fragrant, and produces a lot of nectar making it very popular with bees and butterflies.  In Ontario they open late July around the same time as daylilies. They mature to ball-like fruits with a slight reddish colour, and persist into winter.

Buttonbush normally grows to form a 3-8 foot shrub, which occasionally develops into a taller tree. It is slow growing and can be trimmed to stay smaller. If this is too large for your garden a new cultivar is now available with the trademark name of Sugar Shack, which has redder fruit, and grows to about 4 feet tall.

Life Cycle: small tree or shrub

Height: 150-360 cm (5 – 12 ft)

Bloom Time: July

Natural Range: Eastern Canada, USA (mostly in the east), Mexico and Cuba

Habitat: swampy wet areas in full sun

Synonyms:  Cephalanthus occidentalis var. californicus, Cephalanthus occidentalis var. pubescens


Light: full sun to part-shade

Soil: any type of soil

Water: even moisture, even standing water

USDA Hardiness Zone: 5-10

Propagation: seed, soft or hardwood cuttings, division

Seedex availability (ORG&HPS annual Seed Exchange): occasionally

Requires light or the small seeds should be surface sown. See
Sow @ 20°C. Seed germinates within 3 months.
Robert Pavlis