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"In Praise of Clethera alnifolia," by the Whistling Gardener

Clethra alnifolia. Photo credit: W. John Hayden, Virginia Native Plant Society.
Clethra alnifolia. Photo credit: W. John Hayden, Virginia Native Plant Society.

This column is being reproduced with the permission of Steve Smith, The Whistling Gardener, and owner of Sunnyside Nursery in Marysville.

We are blessed in the northwest to be able to grow a wide variety of plant material from many other parts of the world (in addition of course to our own native flora). Because of our proximity to Asia and our shared Pacific marine climate, many of our gardens sport plants from Japan (hence the name japonica in plants like Pieris and Euonymus), China (hence the name chinensis found in Wisteria), and Korea (think of the Korean or kousa dogwood that so many of us enjoy).

I even have a hardy Schefflera taiwaniana which obviously comes from Taiwan. Like most people, gardeners are always looking for something new and different that is not locally found. But going what seems like a long way away to find new plants isn’t always necessary. Take for example Clethera alnifolia, or Summersweet as it is commonly called.

Summersweet is a delightful deciduous shrub that hails from our very own east coast and grows along the entire eastern United States. It is most commonly found in moist woodlands and has an upright growth habit reaching five to eight feet tall and four to six feet wide (newer forms are more compact). It tends to sucker, forming colonies, but is certainly not invasive like bamboo. The leaves are a bright, shiny green that turn a fabulous intense yellow in the fall.

What gives Summersweet its name is of course the flowers, which come in either white or pink on three to five inch racemes (think of a radish or mustard flower). In our west coast climate, Summersweet is quite happy in full sun but will also tolerate afternoon shade. The blooms are forming as we speak and should be sporting color before the end of the month and into early August. If you make it into the garden center this month you won’t miss their sweet fragrance wafting through the nursery aisles.

Generally speaking, Summersweet prefers a moist, acidic soil with lots of organic matter - which is precisely what most of us already have (assuming we add some additional compost, which should be an annual ritual anyway). Since the flowers are produced on the current season’s wood (what we call “new wood”) much like a rose, we can prune it hard in the spring if we want to keep it contained. Hummingbirds and butterflies are drawn to the flowers, while deer seem to ignore them. Here are three varieties currently available in the nursery that you might want to consider:

Vanilla Spice — This selection has flowers roughly twice the size of other varieties. Large, fragrant spires of white flowers show up in late July and continue for four to five weeks. Plant one in full sun and you are bound to see a few Swallowtail butterflies visiting them on a warm summer day.

Hummingbird — This is a very popular variety that is more compact, topping out at only three to four feet tall. The dark, glossy green leaves are a nice backdrop for the bright white flowers. As the name implies, hummers (and of course butterflies) will seek this one out in your garden.

Ruby Spice — Possibly my favorite, this has the darkest pink flowers of any of the Cletheras. Everything else about this variety is pretty much the same as the others.

Summer blooming shrubs are so critical to our pollinator populations that all of us should have several in our gardens. Summersweet easily falls into this category, along with roses, hydrangeas and probably one of the latest blooming shrubs for us, the hardy hibiscus or Althea or Rose of Sharon. You can find all of these in garden centers this time of year.

Sunnyside will be hosting two free classes – “Shade Gardening” on Saturday, July 21, 2018, at 10:00 am; and “Hardy Fuchsias” on Sunday, July 22nd, at 11:00 am.

Steve Smith is the owner of Sunnyside Nursery in Marysville, WA, and can be reached at

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