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Local Living: On Gardening

The smoke tree has an easy beauty, says Adrian Higgins

Grace is a smoke tree hybrid with blue-green leaves and purple flower heads.
Grace is a smoke tree hybrid with blue-green leaves and purple flower heads. (Adrian Higgins/the Washington Post)

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By Adrian Higgins
Thursday, June 3, 2010

Each morning, I walk my dog through a neighborhood park whose plants are so forlorn and ill-tended that, to make it through mentally unscathed, I have to view the landscape more as a horticultural experiment than as a pleasure ground.

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The lawn is a greensward of weeds but gets mowed nevertheless, and one learns to squint. The sentinel tree is a ruffian of a thing, the Indian bean tree, or catalpa, an American legume with blowsy flowers followed by coarse pods, along with large, heart-shaped leaves that are distinctive but not pretty. The bean tree is planted liberally around the Houses of Parliament in London, a curious choice and perhaps a reminder of a lost, tough, bighearted colony.

As if in some sort of reverse homage, my local park has several old upright English oaks. They look majestic for a few weeks and then develop powdery mildew. A pair of close-set native persimmons have handsome blocky bark, and fruit reliably, though the trunks seem thin for their age. The place is full of misfits, but survivors. There is no better example than three badly neglected smoke trees. For all their trials -- drought, lack of pruning, impoverished soil -- they look pretty good, especially in late spring, which is when the smoke tree earns its name.

From new stems bearing paddle-shaped leaves, the shrub presents a bizarre plume of hairs, purple up close, a muddy gray from afar. Each inflorescence can be 12 inches long and each branch tip arrayed with a dozen of these plumes. When you step back, you see these parts shrouding the plant in a haze.

If the smoke tree can look so good with neglect, think how fabulous it can be when grown well. Like some of the larger crape myrtles, it can be raised either as a big, multi-stemmed shrub or a small, low, branching tree, with a single trunk emerging from the ground. This is determined before you buy it; you have to look through nursery specimens to decide which form you want. It will grow 15 feet tall and about the same in width, making it valuable as a back-of-the-border plant, or as a large screen that will provide much of the privacy of the Leyland cypress (well, not in winter) without its dull bulk.

Purple forms have been developed, including the longtime dependable variety called Royal Purple. The leaves are a rich dusky purple and remain so well after the first flush of spring growth. This is worth something. The heat of Washington usually renders the rich maroons of purple-leafed trees such as beeches, maples and plums an unsettling shade of puce. Royal Purple won't wimp out in a carefully crafted border of, say, purples, blues, white and silver.

It has become fashionable among connoisseurs to plant lime-green smoke trees, especially a Dutch selection named Golden Spirit. A little afternoon shade will keep the foliage bright chartreuse, a hue that pairs well with blues and violets. Golden Spirit would go nicely behind the catmints now in bloom and, in a few weeks, the Russian sage. You could prolong the effect with caryopteris and late-season salvias.

It would also be fun to grow climbers into smoke trees. I have a rose named Chevy Chase, profuse with small, crimson red blooms, that would perch nicely in a Royal Purple. And there are lovely indigo-flowered clematis that would look spectacular entwined with smoke trees. I am thinking of Clematis x durandii, which grows to about eight feet with four-inch flowers that are a rich deep blue. It has been blooming for me for the past month.

The other day, I encountered a large, bell-flowered clematis that cries out for a starring role in a supporting smoke tree. Clematis Roguchi is related to durandii and is mouth-wateringly beautiful. It is sometimes sold as Rooguchi.

But back to smoke trees. (Those clematis can be so distracting.) There is a hybrid between the Old World smoke tree and the native species named Grace that is an extraordinary plant in itself. The leaves are longer and narrower than Royal Purple, appearing a light bronze in the spring but turning a blue-green with marked maroon stems and veins at this point in the season. It grows to about 20 feet or more and would make a rugged street tree, I would think, or a great substitute for the overplanted Natchez crape myrtle.

An entirely different way to grow smoke trees is to cut them back like perennials in the winter. This forces vigorous growth in the spring, but only to six or eight feet. Grown this way, you would lose most of the flowers, but you would have a striking foliage plant, a screen for the urban garden and a foil for smaller plants such as hostas, daylilies, amsonias or the different and commendable spirea varieties Ogon or Magic Carpet, or the deutzia Nikko.

Some gardeners will cut the smoke tree back every other winter, which provides for flowers in the second year. But you have to keep up this regimen once started. Smoke trees that are pruned back and then left are like apple trees: They produce rank growth that gives them a weird look. The plumes top bare stems that erupt from the canopy of the shrub, each branch growing as long as 10 feet in a year. The effect is interesting but lacks purpose.

Smoke trees go out with a bang, many varieties sporting beautiful leaf colors in the fall. The purples turn red and the light green ones a combination of orange and red and yellows. Something to ponder next time you walk your dog.


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