From wild to wonderful, pesky plants can please

Some people love weeds; others hate them.
KNIGHT RIDDER NEWSPAPERS
They have cool-sounding names right out of "Harry Potter": pennywort, teasel, henbit, vetch.
And some are downright stunning: the sweet mosaic of Indian strawberry, for example, or the snowy star-of-Bethlehem.
Come spring, a carpet of stars and strawberries in the backyard garden may seem colorful relief from the dreary brown of winter. But then we're rudely reminded what they really are: weeds. Botanical beasts crowding out the plants we want to grow, multiplying like crazy despite our brutal attacks.
Even figuring out what qualifies as a weed can be confusing. In another setting, another time, these plants might not be considered weeds. But here and now, they're unwanted, uninvited.
"A weed is a plant out of place," explains Sinclair A. Adam Jr., senior lecturer in landscape architecture and horticulture at Temple University Ambler.
What is it?
It's a plant that likely was brought here deliberately from another part of the world, or arrived accidentally, and that once established in its new environment can pack a "bang zoom" of a wallop, Adam says.
Being out of place has its dark side: Weeds can cause a lot of damage by squeezing out valued native plants and flowers, fields and woods. They usually spread aggressively -- by seed, root or stem -- and are very prolific, with a single plant capable of producing thousands of seeds.
They're carried by little parachutes and pontoon-type thingies to navigate wind and water currents. They stick to shoes, fur, clothing and feathers. They have needles, hairs, hooks and spines that glom onto everything in sight. They're in animal and bird droppings, on tire treads and insects, and in topsoil, compost and seed mixes.
"Weeds are always on the move, and they're survivors. They adapt," says Stephen Hart, weed scientist at Cook College, Rutgers University's agricultural school.
So it's no mystery why we have so many weeds. It may be a miracle we don't have more.
Some like them
But not everyone hates weeds. Some people eat them. Some consider them medicine or celebrate their beauty. As Adam likes to say, "One man's meat is another man's poison."
Take the common dandelion. It may be loathed by gardeners, but some folks grow it for salads, soup, jelly and wine. Thought to have come from Europe and Asia, it has also been touted as a tonic for everything from warts to cirrhosis.
Pam Mann, who cultivates two of her 6 1/2 wooded acres in Chester County, Pa., actually "plants another common weed in her garden -- dame's rocket ("Hesperis matronalis).
Why? "Because I think it's beautiful," Mann says.
And it is, with its tall, phloxlike stems of purple, pink or white flowers that smell especially sweet at night.
Dame's rocket, which arrived in North America from Europe in the 1600s, is seen more often along the road, in ditches and meadows, than in gardens. If given half a chance, it pushes out native wildflowers.
Keeping an eye on it
But Mann has plenty of space for it in her garden, and she keeps a watchful eye so it doesn't get out of hand.
She's far less tolerant of ground ivy, which also came from Europe and is more aggressive.
"It's just a nuisance, and it'll take over your garden and choke everything," Mann says.
She yanks out the ivy and the Japanese honeysuckle, along with the onion grass, which hails from South Africa. Then, several times over spring and summer, she uses a shovel to make a clean edge between the flowerbeds and grass. That keeps undesirable roots from creeping in or out, and "you can see what's coming," she says.
Basically, Mann describes a love-hate situation in her garden every spring.
"You want to dig up all the ground around your established plants to get the weeds, but if you do, you won't have the pleasure of seeing all the little seedlings" your good plants give off.
It's a delicate chore. She painstakingly lifts each perennial out of the bed, removes the weeds around it, and puts the perennial back. She also uses leaf mulch to keep the weeds down.
"The main idea is to stay on top of it," she says.
Understanding ecology
Managing weeds is critical, it's true. But gardeners should also appreciate the ecological role weeds play as bird feed or animal cover, says Antonio DiTommaso, a Cornell University weed scientist.
While some weeds are extremely damaging and cause health problems such as poison ivy, he says, others are pariahs simply because they interfere with human activities -- like playing golf, building new homes, or creating the perfect lawn.
"I think I could find a role for any plant," says DiTommaso, who defines a weed as "a plant whose virtues have not yet been found."
Some plants now labeled with the W word were once touted as problem-solvers. Multiflora rose, a Japanese native, was promoted by the U.S. Soil Conservation Service in the 1930s as an effective "living fence" to control livestock. More recently, it's been used as a highway safety barrier.
Sooner or later, we learn that "these are not team players in our communities," says Mark R. Gormel, horticultural coordinator at the Brandywine Conservancy in Chadds Ford, Pa. "They disrupt what was a balance that went on for thousands and thousands of years."