Grading ground cover

Ground cover is one of those terms that one suspects would sound so much better in French. Couvert de la terre. The sheer bluntness of the American name only reinforces the lowly status of the class of plants -- below trees, below shrubs, below borders, below even lawn.

But sometimes the most impressive plants in the garden are beneath our gaze, tucked along a path, running under a tree. Ground covers not only are appearing in ever more tantalizing variety, they also are useful in every garden. They keep down dirt, control weeds and hold earth in place. Choose the right one and it can serve as visual glue and provide color, texture, variety, beneficial insects, scent and even cut flowers. Select the wrong one and you can become embroiled in a battle to either keep it alive or contain it.

The No. 1 American ground cover, of course, is lawn. But pity the parvenu who calls it ground cover. Centuries ago, landscapers managed to transcend the term by concertedly mimicking the manicured estates of England. The rituals of lawn care now so define American gardening that one of the warmest recommendations a nurseryman will give a ground cover is "You can mow it."

You can mow oregano too, says V.J. Billings, founder of Mountain Valley Growers, a Fresno, Calif., herb farm that has made considerable inroads selling herbs as landscaping plants by mail order. It sells half a dozen creeping, crawling and mounding oreganos suitable for ground cover and no fewer than 18 ornamental thymes.

Groupings of herbs make beautiful beds, but it's hard to call them ground cover rather than bedding plants. They do meet the definition when they are planted along pathways and steps, and when they tumble elegantly here and there. The best are scented and bruise fragrantly underfoot.

A variety called Steppables sold at Sunny Hill Garden Center also fits the category of groundcovers. The plants, like creeping thyme, also emit light scents when crushed.

But in Southeast Missouri, some of the most popular ground covers are vinca, English or hardy ivy, pachysandra and creeping junipers.

Gardeners and homeowners often choose these plants because they're trying to limit their mowing but also because they have a more natural look in the landscape, said Paul Schnare.

"More of the finished landscapes have a lot of ground cover," Schnare said.

Ground covers help with weed control and erosion control.

For Billings, the truest characteristic of a ground cover is the ability to spread. Creeping capability can be assessed at a glance, she says. Look for leggy shows of stem. A vigorous creeper will need to flop, touching its stem to the ground, where it can send down new roots. The more vigorous a creeper, the more space it will have between its leaves, so the foliage doesn't get in the way of the flopping, grounding and rooting.

As a working rule, the closer set the leaves, the slower a plant will creep; the farther apart, the faster.

But some plants are chosen for their ability to spread quickly. A variety of liriope is known for its spreading qualities. Liriope spicata is often used to fill in beds and borders because it spreads, Schnare said.

Some gardeners also like to use primrose or crown vinca as ground cover because the plants also sprout flowers.

The Los Angeles Times and features editor Laura Johnston contributed to this story.