Of all the functions plants serve in the landscape -- ornamental enhancement, providing shade, ground covering and screening among other things -- rarely is any attention paid to their value as conversation pieces.
Oh, the beauty or fragrance of flowers, or the foliage or form of a tree or shrub might elicit comment, but there are other plants to exclaim over for different reasons, and the more of them you become acquainted with and grow, the more fascinating your garden will be.
What started me thinking about all this was a visit I made a couple of months ago to White Flower Farm in Litchfield, Conn. On a tour of the place, I saw a gas plant for the first time. The name alone is enough to start a person wondering. I thought about the stir the plant would make if at a dinner party, I were to lead my guests to one in my garden, casually hold a lighted match close to it and let them watch as a blue flame burst through the flowers and burned itself out, leaving them untouched. The experience makes you think of lighting a pilot light on a stove.
But for the gas given off by the plant to ignite, the weather must be hot, humid and calm and the space in which the plant is situated should be somewhat confined. Even then, the trick might not work.
The gas plant is a perennial whose botanical name is dictamnus. It's colors are white, D. albus; purple, D. purpureaus; and red, D. rubra. However, because plants are propagated from seed, says Alan L. Summers, president of Carroll Gardens in Westminster, one of the very few nurseries that offers the plants, you can't tell for sure what color the flowers will be. Emerging stems are the clue; green ones indicate white blooms, purple-tinted ones are a sign of colorful blossoms.
So highly is the gas plant rated that some gardeners declare they wouldn't be without it. And yet cultivating it, at least in the early stages, requires perseverance. Plants are hard to get established and once they are, their 8-foot-long taproot makes them practically impossible to move. For that reason, plant dictamnus where it can stay.
If you must relocate it, do it while the plant is dormant. Also mark its place so you don't dig into it in planting or cultivating the bed. Provide dictamnus with fertile, well-drained soil and full sun or light shade, and once it settles in, Mr. Summers says, "it will last forever." One plant in the annals of horticultural literature is said to have outlasted three generations of the family that grew it.
If you're adventurous, you could try starting dictamnus from seeds. Because seeds require a long period of cold to germinate, sow them in a cold frame (where they won't be washed away) in November, says Dave Anderson, a horticulturist at Park Seed, a source of seeds. Mulch the bed after the ground freezes, and remove the mulch before plants poke up in the spring.
Thin plants or transplant them after they've gained a few inches in height and increase the spacing again the following spring. Put plants in their permanant home the season after that. They should begin to bloom regularly in June and July from then on. Plants obtained as nursery stock -- as at Carroll Gardens -- are available in the spring. But because dictamnus is choice and scarce, supply is limited. The plant, by the way, especially the seed pods, is poisonous.
If the gas plant's effluence can catch fire, smoke tree or smoke bush -- Cotinus coggygria -- merely smokes. At least that's what the plant appears to do when it's in flower. The effect is produced by the tree's large fluffy fruiting panicles that might be described as resembling cobwebs. They develop in early June and last until fall. Royal Purple, one of the preferred cultivars for its striking shade of foliage and deep pink plumes, is described in nursery catalogs as "dramatic for the shrub border" and "a conversation piece." In her book, "Perfect Plant, Perfect Garden," Summit Books; $24.95), Anne Scott-James includes it on her list of the "200 most rewarding plants for every garden." Velvet Cloak is another preferred cultivar.
The smoke tree also looks nice on a lawn. Its 15-foot size suits it to patio planting or as a background for a flower bed. Or you could group trees at the corner of a property. By positioning the smoke tree so the sun lights it from behind, the leaves will take on a sort of iridescent effect.
A member of the cashew family, the genus Cotinus takes its name from kotinos, the Greek name for olive. No one can explain the reason. There's no mystery, however, when it comes to the species name, coggygria: it derives from kokkugia, in Greek, meaning smoke.
C. coggygria refers to the European smoke tree, one of the two species in the genus. Native to southern Europe and central China, it is hardier and far outshines in its degree of smokiness its sister, the American smoke tree or C. americanus. The American smoke tree is twice the height of the European version, and although the panicles are less showy, the native smoke tree is among the most brilliant of all woody ornamentals for fall color.
This long-lived plant (the oldest smoke trees at the Arnold Arboretum in Jamaica Plain, Mass., recently celebrated their 102nd birthday and are still going strong) is among the easiest to grow. Although in its early years it needs to be watered and perhaps mulched so the roots don't dry out, once it grabs hold, it needs little or no care and even tolerates some drought. It's content with ordinary soil, as long as it's well-drained, and it prefers full sun. The European species withstands cold better than the American one.
The smoke tree can be planted in the fall. As a rule, it develops as a multistemmed trunk. However, if you wanted it to look less like a bush and more like a tree, you could train it to a single trunk by removing the extra stems while the tree is still young. Also, its branches are set fairly low. Mr. Summers says that if you wanted to sit beneath the tree for shade, or need to mow under it, prune the limbs while the tree is in its infancy.
Three nurseries offering Royal Purple for fall planting are Carroll Gardens, 11 E. Main St., Westminster; Behnke Nurseries Co., 11300 Baltimore Ave. (U.S. 1), Beltsville; and Maxalea Nurseries Inc., Oakhill and Sherwood roads, south of Towson in Stoneleigh.