Fragrance Underfoot

By BARBARA PLEASANT

Is it a pathway or a garden? A stone walkway in which numerous crevices give rise to pretty plants always begs the question, especially in summer, when fragrant herbs and flowers are at their peak. But in winter, when most of the plants recede into dormancy, the stones take over the scene, and the notion that the place is, indeed, a garden fades to a whisper.

The concept of a stone walkway that also supports plants is open to endless interpretations, with one or the other element receiving primary emphasis. If the stones are set over soil, with only enough sand or paver base beneath them to help keep them level, you can even change things from year to year, adding and subtracting stones or plants according to your gardening plans for the coming season. Some gardeners find such delight in having plants arise between stones that they find places for them everywhere, including the center of the walkway, so that actually using the corridor forces you to take a series of mincing steps. Yet logic and reason suggest that all upright plants should be limited to the walkway’s outer edges, with only ground-hugging dwarfs allowed to claim the middle ground.

For many gardeners, the greatest challenge of creating a walkway that prominently includes plants is to avoid the appearance of messy chaos. One obvious approach is to limit crevice plants to one or two species, such as creeping thyme in the sun or sweet woodruff in the shade. Then, along the edges, you can organize plants according to a rhythmic, linear plan. Place similar plants on opposite sides of the walkway, so they appear to echo each other across the path. Include an intermittent edging of curly parsley, dwarf basil, mound-forming dianthus, or other naturally neat plants. Finally, since paving stone is often gray, broaden the color band by growing drifts of artemisia, dusty miller, sage, or other gray-foliage plants along the walkway’s edges.

Keep in mind that during the winter you will be looking at bare stone. Because of this, some type of pattern in the placement of the stone will be welcome, so it’s wise to keep your ideas about plants on the back burner until the walkway itself takes shape. To allow for future changes, compose the walkway so that large stones occupy the center, with smaller stones nearer the edges where you are more likely to place plants. It’s much easier to lift a small stone to pop in a plant than to custom fit a stone into a hole that insists on sprouting up in weeds.

As much as I would like to tell you that this type of garden is easy to plant and maintain, this is simply not true. Because of the way stones hold on to heat in summer and cold in winter, finding plants that are happy in any particular site is often a trial-and-error process. The plants described on pages 28 and 29 are a good place to start, but you should also visit public gardens in your area to learn about well-adapted species and cultivars. Of course, when you do find a plant that likes your walkway, you are wise to capitalize on this discovery by planting it more widely.

Weeds also can be a nuisance, and I don’t consider chemical control to be a reasonable option when edible plants are grown nearby. If you let weeds grow too long, their roots become so extensive that you can easily pull stones loose while weeding, so the only solution is to weed early and often, all the while plugging in plants that grow so tenaciously that they cover places where weeds would otherwise appear.

Comely plants for crevices

The crevices in a stone walkway are particular niches that call for plants that are specially adapted for such locations. In addition to having a dwarf growing habit that won’t trip you up as you walk along, crevice plants must hug the ground and spread sufficiently to form green seams between the stones. Plants that spread too much may be wonderful for growing in a stone wall or allowing to sprawl into the nooks and crannies of stone steps, but they will hide the beauty of stones installed on a flat, level plane. On the other hand, those that spread too little give weeds opportunities to poke through, making maintenance a constant headache.

The plants described here grow to less than 6 inches tall and have a proven track record of success in pathways in various climates. Still, expect some failures as you seek out great plants for crevices, because not every species that is supposed to do well will live up to its reputation. To increase your chances of success, begin with healthy, well-rooted plants, and set them out when they are poised for vigorous growth. In most areas this is early spring, but fall planting is often preferred in Zones 7 to 10. Finally, be forewarned that the same tenacity that helps crevice plants hold their own between hot walkway stones can make them a nuisance if they escape into flower beds.

Ajuga (Ajuga reptans)

Also called carpet bugle or bugle weed, ajuga has spoon-shaped leaves that grow into round rosettes that spread by stolons. Blue flowers on short spikes appear in spring. Hardy to Zone 3, ajuga will grow as far south as Zone 9 in shady, well-drained locations. For walkways, choose cultivars that grow no higher than 6 inches. For the most natural effect, allow ajuga to form thick mounds along walkway edges, with a few plants creeping inward to fill crevices.

Bellflower (Campanula spp.)

Bellflowers vary greatly in size and habit, and also in the shape of their flowers—some really do resemble bells, while others are tubular or, like those of C. fenestrellata, star shaped. This dwarf, mat-forming species of bellflower grows to only a few inches high, produces profuse racemes of small, bright blue to lilac flowers, and is adapted for zones 4 to 7. Perfect for a well-drained spot in a paved walk, bellflowers could also be tucked in along a stone wall.

Pinks (Dianthus spp.)

Many kinds of Dianthus are natives of alpine areas, so they are well suited for rocky, well-drained areas of your garden, such as on a pathway. Smaller, mat-forming varieties of pinks, such as D. microlepsis, D. glacialis, and D. pavonius, produce 1/2- to 11/2-inch-wide pink or purple flowers each summer above tufts of silvery gray to green leaves. They prefer acidic conditions, and they really don’t like to get their feet too wet, so keep them out of spots with standing water in winter.

Alpine liverwort (Erinus alpinus)

Ideal for crevices in paving or stone walls, this tufted, semi-evergreen perennial is a native of the mountains of central and southern Europe. It produces short racemes of pink, purple, or white flowers 1/2 inch across from late spring to summer, grows about 3 inches high, and is adapted to Zones 4 to 7. For deep pink flowers, try the cultivar E. alpinus ‘Dr. Hähnle’. Alpine liverwort needs light to moderately fertile, well-drained soil in full sun or partial shade and very good drainage.

Sweet woodruff (Galium odoratum)

Although this delicate ground cover reaches 6 inches in height when it blooms in late spring, a light shearing in early summer will keep the scented leaves at a more manageable 4-inch height. Best in moist shade, sweet woodruff is hardy to Zone 4 and will grow in cool woodlands as far south as Zone 8. This is an ideal plant to grow in drifts along the edges of a shady stone walkway, with creeping stems and volunteer seedlings allowed to spread slowly inward between crevices.

Cranesbill (Geranium spp.)

Cranesbills are the more than 300 species of the genus Geranium. (The plant commonly known as the geranium is in the genus Pelargonium.) Cranesbills that might accompany you along a garden path include G. dalmaticum, a dwarf, creeping variety about 6 inches high with glossy green leaves and pale to bright pink flowers. It is adapted in Zones 5 to 7, and is evergreen in all but the severest winters. Another choice is G. farreri, with red stems and cup-shaped pale pink flowers, 5 inches tall. Both species grow best in humus-rich, sharply drained soil in full sun.

Corsican mint (Mentha requienii)

Most mints are so aggressive that they will quickly overtake a walkway, but not little Corsican mint, which features dainty, 1/4-inch-wide green leaves that grow into a fine-textured mat less than 1 inch tall, topped by light purple flowers in midsummer. Adapted in Zones 6 to 9, this mint requires excellent drainage and tends to suffer in extreme heat with no break from the midday sun. It offers a fine minty fragrance, so it’s worth trying in different spots to find a place that suits its needs perfectly.

Creeping oregano (Origanum vulgare ‘Compactum’)

This spicy herb needs full sun and good drainage, but few crevice plants have as much to offer in terms of fragrance and longevity. Adapted in Zones 3 to 10, the plants become dormant in winter except in mild climates, where they are often evergreen, darkening to a purplish color in cold weather. The dainty flowers produced in midsummer attract bees and other beneficial insects.

Soapwort (Saponaria ¥‘Bressingham’)

Originally from the meadows and rocky, mountainous areas of Europe and southwest Asia, soapwort requires gritty, sharply drained soil. The hybrid ‘Bressingham’ grows to 3 inches high, and its many short-stemmed cymes carry brilliant deep-pink flowers. It is adapted for Zones 5 to 8. Besides poking out of a walkway, soapwort is also a good choice for growing in rock gardens and in stone troughs. Its common name refers to the fact that its leaves can be used to create a mild soap.

Woolly thyme (Thymus pseudolanuginosus)

Expect confusion in botanical names when shopping for woolly thyme, which goes under several names. All varieties have soft gray-green foliage that grows to less than 4 inches high, spreading into mats in hospitable places that have excellent drainage and some protection from the baking sun. Adapted in Zones 4 to 9, this thyme releases a refreshing herbal scent when crushed underfoot. After the small blooms wither in midsummer, shear the plants back to help them maintain a tight cover of foliage.

Barbara Pleasant is the author of The Gardener’s Bug Book (Storey, 1994), The Gardener’s Guide to Plant Diseases (Storey, 1995), and The Gardener’s Weed Book (Storey, 1996). This text was excerpted with permission from her most recent book, Garden Stone (Storey, 2002). Pleasant is currently the author and publisher of the Alabama Gardener’s Almanac and a member of the Garden Writers Association of America.