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Stick With Plants That Do Well in Washington

Transplanted Gardeners Need New Roots

By Adrian Higgins
Washington Post Staff Writer
Thursday, February 17, 2005; Page H01

If you think certain plants don't like transplanting, spare a thought for the gardener.

Washington is traditionally a city of transplants, after all, many of them yearning for the landscapes of somewhere else. The desire is to emulate what was left behind. Understandable, but often a path to regret.


Hybrid lupine 'the Governor:' An unhappy camper in Washington.

Virtually every plant I grew up with in boreal England will not flourish in a climate that is both colder in winter and hotter and muggier in summer. Here, the same primroses fade away, the lilacs get blasted by April heat and dusted by summer mildew, the horse chestnut tree develops leaf scorch, the hydrangeas are grudging, the trailing lobelia is fleeting and the plume poppies a joke.

How do you know if the buffed roses or bright perennials leaping from the page of a shelter mag will work here? One way is to consider your plant hardiness growing zone. In most of the Washington region that's Zone 7, with average winter lows of between 0 and 5 degrees Fahrenheit. But this only gets to winter hardiness, not whether a plant will thrive in regions of high summer heat and humidity. Birch trees, for example, grow sick in our sauna.

The Alexandria-based American Horticultural Society has tried to address this by also labeling plants by heat zone limits, listed in its books (the latest being the A-Z Encyclopedia of Garden Plants, DK Publishing, $80).

Lots of plants at local nurseries will do well with proper care, but not every plant offered for sale thrives or survives in the local climate and soil conditions.

Talking to other local gardeners is one of the best ways of finding out what will or won't grow. The best teacher is your own failure, but by then you've already invested your money, toil and dreams in a loss.

With spring a month away and plant cravings beginning to build, it might be worth considering some of the unassailable duds of the Washington garden.

Heaths and heathers evoke English rock gardens and Scottish glens, but cold winters and hot summers make these lovely flowering ground cover shrubs short-lived, even if the gardener has provided the preferred soil conditions of peat and sand. Heaths are attractive additions to large containers planted for fall and winter ornament, but are best discarded when the pot is reworked for the summer.

Sweet peas evoke something particularly nostalgic with their long garlands of scented flowers in pastel blues, pinks, lavenders and whites. But they grow poorly hereabouts even when the gardener goes to the trouble of starting them in the fall and pinching out the seedling's leader. In cooler climes with longer summer days, the vines grow tall and floriferous, but here the heat of May stunts them as they prepare to climb and bloom.

Franziska Reed Huxley, who gardened in Chevy Chase for several years before moving to Pennsylvania, made the mistake last June of visiting one of England's finest rose gardens in peak bloom. The roses were magnificent, including once-blooming ramblers and climbers of amazing size and floral adornment. These roses, dare we say it, were without blackspot. But it was another plant altogether that turned her green: a blue flowering evergreen shrub named ceanothus. The choicest varieties grow high and in Britain the plant is used as a "wall shrub" -- essentially a climber to soften some wonderfully high masonry edifice. In June and July it is smothered in lilac-like panicles in various shades of blue, depending on variety, and more intense and clearer than the blues of other shrubs.

The plant is native to California, but isn't tough enough for Washington winters. If it did survive, other frailties would surface.

Huxley notes that in northern climates, where the summer days are long and the evenings cool, plants tend to bloom for twice the period they might in Washington. And the same conditions seems to bring out a greater robustness, witnessed in such northerly states as Iowa or Maine. The classic example is the delphinium, whose blue spikes can reach to six feet or more in northern gardens. Its cultivation is rarely attempted at this latitude and then only once.

Another such border perennial is the hybrid lupine, whose bright clusters of pea-like blooms add form and height to the flower border. But it is feeble in hot summer areas even if this point is ignored by seed merchants and plant catalogues. A native lupine, small and blue, will grow here but it is a wilder, daintier creature than the hybrid lupine.

For years, a friend has been trying to get me to grow gunnera or giant rhubarb at his pond in the country. This is a lakeside monster, with possibly the largest leaves of any terrestrial herbaceous plant. Each fall, it dies back to its crown, and in Europe and the Pacific Northwest, where it grows well, its caretakers remove the leaves and use them to blanket the crown. If the crown and roots freeze, the giant dies.

In Stonecrop, a public garden in Cold Spring, N.Y., gardeners go to great lengths to produce an East Coast version. This involves placing a large wooden box over the roots in November. Measuring approximately 12 feet by eight feet by six feet, the box is double skinned and insulated. The roots are blanketed, and the box is filled part way with packing peanuts. Wood chips are banked against the exterior of the box, said Steve Johnson, Stonecrop's superintendent. He slowly acclimates the emerging leaves in the spring, and after several weeks of lifting the lid during the day, the box is removed for the growing season.

Johnson thinks you could grow it in Washington by just smothering the crown in a winter mulch, though he concedes it is a plant that requires devotion. Gunnera is found like a weed in upland swamps of Brazil and Columbia even if it has come to define the large water garden of English country estates. It is conceivable that an Anglophile in Washington would go to extraordinary lengths to raise an Amazonian rhubarb to evoke a Palladian pile in Dorset, but it won't be me.

It is not only migrants from northern climates that find the Washington garden a challenge: Southerners lament the precarious conditions for gardenias and camellias and jasmine, which are at risk from winters outdoors but are too hardy to like life as a houseplant.

And yet, as frequent travelers know well, the Washington garden is lush, has a long growing season, and cossets plants that others would kill for, including the flowering dogwood, tender salvias and the tomato plant. Water is abundant in most years, which cannot be said in Colorado or, for that matter, the English Midlands.

It is fun to try plants that remind us of our roots, but it is unwise to base a garden on them. Better, perhaps, to work with what we have, safe in the knowledge that gardeners around the globe are worrying too about weeds, which know no boundaries.


© 2005 The Washington Post Company