Viburnums, few others among shrubs that thrive in wet soil
Posted: Tuesday, January 26, 2010 8:01 pm
By: By Jimmy Williams
Poor drainage kills more plants than just about any other evil. Our clay soil is notorious for poor drainage and deep digging and the addition of gravel or other ingredients to add porosity is just about the only solution.
The only other way out is to grow things that will stand the wet. All the trees mentioned here last week will do that. There are some few shrubs that will also.
Viburnums are some of the most valuable shrubs around. We have a number of species and varieties of them, several of which are growing in our damp garden.
The doublefile viburnum, Viburnum placatum tomentosum, has been extolled here before, but I repeat it is one of my favorite large shrubs or, if pruned up and out, small trees. The doublefile bears, as the common name implies, blooms, as well as leaves, in double file along the branches.
The flowers, white lacecaps, follow on the heels of dogwoods nearby and continue the show. Doublefiles have done very well in wet areas and, in fact, should be watered heavily the first few years after planting. Even old ones suffer from drought.
Other viburnums that take virtually swampy conditions are the arrowwoods. American natives used the straight shoots of these for arrows and they can be found in the wild.
A number of named varieties of arrowwood are available in nurseries. In recent years Blue Muffin has become popular. It stays at about seven feet and bears blue berries.
Several interspecific hybrids abound. I recently planted Conoy, which is evergreen, or almost so, and grows to five feet or so. Conoy bears red berries and the leaves turn maroon in cold weather.
Oregon holly is not a holly, but Mahonia bealei, or leatherleaf mahonia. It is very common and has broad evergreen leaves divided into leaflets. It has thrived in wet places and shade. Spires of fragrant yellow flowers redolent of lemons emerge from the six-foot stems in late winter or early spring. An uncommonly attractive shrub for shade and wet, this mahonia will burn and bleach in hot sun. A new race of mahonia hybrids has expanded bloom time into fall, but many of these are not winter hardy here. I have two different ones that bloomed in November and December, but I have my fingers crossed.
Sweet pepper bush, Clethra alnifolia, is made to order for shade and wet. In fact, its native habitat is swamps and low places in the eastern U.S. Its value lies in its late summer bloom, August to wit, when few woody things are blooming, and even fewer in deep shade. That’s when sweet pepper bush shoots up spires of white or pink flowers from the tip of each stem. That would be enough, but the little flowers emit an intoxicating sweet fragrance that carries on the humid air of that time of year. Then, in fall, the leaves turn a bright yellow.
Sweet pepper bush will grow to 10 feet or more, and sucker modestly into a thicket after many years. A fine pink form is Ruby Spice, with all the fine attributes of the usual white one.
A Japanese version, Clethra barbinervis, grows taller, to 20 feet, and has exfoliating polished bark on older specimens. Some fellow gardeners have believed one of mine is that species, but in fact it is a later blooming form of the American clethra that doesn’t provide flowers until late August into September.
Editor’s note: Jimmy Williams is production superintendent at The Paris Post-Intelligencer, where he also writes this column.
Published in The Messenger 1.26.10
Jimmy Williams, The Garden Path