WRITTEN BY VALERIE EASTON ILLUSTRATED BY SUSAN JOUFLAS

Perhaps mistakenly, we think we can figure out human ethnicities by appearance; plants, however, reveal little about themselves. We learn about their origins mostly by observing how plants thrive or not in the conditions where we plant them.

This global array of plants offers a richness of choice that is the envy of gardeners around the world. It can also result in biological pollution, for some immigrant plants, while they may be good citizens at home, run amok when freed from their naturally occurring enemies and introduced to generous Northwest growing conditions.
 

Now In Bloom Sunflowers (Helianthus annuus) with their bright colors and distinctive, bold shapes, enjoy hot, well-drained conditions. Kids love them because they grow so impressively tall and bloom atop hairy stalks, and their flowerheads curiously turn to follow the sun throughout the day. Also, sunflowers are easy to grow from seed, and then later their heavy heads droop with seeds that can be roasted or fed to the birds. H. annuus 'Ring of Fire' (above) has a large, dark eye set off by red and yellow petals; 'Sunbeam' is lemon yellow, and 'Teddy Bear' grows to only 3 feet and is appealingly shaggy and golden.

Kudzu, that King Kong of invaders that has blanketed the southern United States and been spotted as far north as Vancouver, Wash., hails originally from Asia. But so do many of our most lovely and mannerly plants such as the white-flowering dogwood Cornus kousa, many of the magnolias and most of the rhododendrons.

The state defines noxious weeds as non-native plants that are aggressive, competitive and highly destructive. While most plants brought to our shores are none of these, it is nevertheless a good idea to be thoughtful and cautious about the potential for invasiveness. And lest we feel a tinge of self-righteousness, remember that our native plants, when introduced into other countries, have often proved to be obnoxious. "Our native plants are bad boys when they go overseas," says Sarah Reichard, assistant research professor at the University of Washington and an international expert on invasive plants. Douglas fir, salal and Oregon grape have all caused problems in parts of Europe, where they have spread too far, too fast.

For centuries, plant explorers have collected seed from around the world to satisfy our thirst for novelty, change and excitement in the garden. These adventurers harvest seed from wildlands on nearly every continent, propagate plants and then market them so new species are continually introduced into the trade. Plant collecting has gone on for so long and been so successful that we don't even know anymore how many familiar Northwest garden staples in fact hail from foreign shores. Various types of birches are native to China, India, Japan and Europe, as well as areas of the United States. It's easy to forget that the common forget-me-not hails from Europe, and forsythia is native to China and Korea. There's only one kind of rhododendron, R. macrophyllum, native to our area; nearly all the species we grow here originate in Asia.

So how do we manage to exert a little discipline and discretion when such an abundance of plants is available to us? It helps to remember that in nature, plants grow in communities of individuals with similar needs and requirements, not unlike human communities. British garden authors Noel Kingsbury and Keith Wiley write about the value of working toward a "visual ecology" in our gardens. To create beautiful, naturalistic gardens, they advocate grouping plants that look as if they could well be found growing side-by-side in nature. This is one way to cultivate a healthy garden while eliminating the visual cacophony that results from planting rosemary next to bog-loving rodgersia, or a tropical-looking canna alongside an expanse of sedum.

By being vigilant about invasiveness and thoughtful about plant origins and communities, we can make a little less work for ourselves, do our small part to prevent biological pollution, and revel in the vast international palette of plants that grow so well here in our mild and hospitable corner of the country.

Valerie Easton is a Seattle free-lance writer and contributing editor for Horticulture magazine. Her e-mail address is valeaston@comcast.net. Susan Jouflas is The Seattle Times assistant art director.

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