Japanese Sweet Shrub:
Clethra barbinervis
B y N i a l l D u nn e
HIDDEN TREASURE OF THE ARBORETUM
I
first encountered Clethra about 20 years ago,
while working at Brooklyn Botanic Garden
in New York. It was a sunny, summer day,
and I was strolling around BBG’s colorful and
expansive rock garden. Just as I was exiting the
garden, I was brought to a halt by the sight—
and intoxicating perfume—of a medium-sized
shrub in bloom along the path. It turned out to
be sweet pepperbush, Clethra alnifolia, a decid-
uous plant native to the eastern U.S. The shrub
was covered in long, narrow, upright spires of
tiny, white flowers, and these were swarming
with bees of all shapes and sizes. I was cap-
tivated, and the sweet pepper bush became a
favorite of mine to re-visit over the eight years I
spent at that garden.
When I started working at Washington Park
Arboretum in 2007, the first Clethra I noticed
was an impressive shrub cluster at the path inter-
section immediately as you walk over the Wilcox
Bridge, heading west toward the Montlake
neighborhood. It was late July, and the seven-
foot-tall plants (now about eight feet tall) were
blooming beautifully—and fragrantly. The plant
tags read C. barbinervis, the Japanese sweet
shrub, and the accession date for all three was
1979. They looked similar to sweet pepper bush,
but the flower spikes were drooping (rather than
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