Ithaca Journal Article: Fabulous Foliage

Fabulous Foliage
By Mary Hirshfeld

Flowers-their color, shape, arrangement, and duration-are key in selecting and placing herbaceous perennials in the garden. Although highly valued and eagerly anticipated, they last for only a small part of the growing season, leaving in their wake an arrangement of leaves that can either be visually stunning-or nondescript. Plants with bold, colored, or intricately formed foliage can be combined to create a soothing yet complex garden tapestry in which flowers are a welcome addition, but not a critical element. Of course, hostas come immediately to mind as the first choice for a foliage plant. But because they offer such an astonishing array of colors, sizes, and shapes, they require an article all to themselves.

The spiny bear's breech (Acanthus spinosus) is a plant that commands attention at all stages of growth. It's glossy, deeply incised, thistle-like leaves rise stemless from the ground, gently arching to form a neat knee-high mound. A native of the Mediterranean region, bear's breech does well in a sunny site with well-drained soil. Although content (albeit a bit more floppy) in partial shade, it will not persist well in heavy, wet soils because it will fail to overwinter well. These plants develop coarse, heavy root systems that run very deep with age and are remarkably persistent. Once you have Acanthus you have it almost forever, since each piece of root left in the soil after removing the plant can develop a vegetative shoot and thus a new plant. As an added bonus, Acanthus produces stunning two-lipped purple and white flowers in midsummer, held aloft on three to four-foot-tall stems.

Goatsbeard (Aruncus dioicus) is another plant with an imposing leaf presence. Those large compound leaves clothe an impressive five-foot-tall, three- to four-foot-wide plant that has the landscape presence of a shrub. Goatsbeard is a remarkably adaptable plant that is at home in sun or shade, in both wet and dry sites. It will agreeably self-sow when the opportunity presents itself. The original streamside planting at the Treman Woodland Walk has provided surprise seedlings both in very dark, dry spots beneath mature hemlocks, as well as perched on rocks in the streambed with their roots dangling in the running water. In bloom, Aruncus is pleasingly subtle, carrying slender branched spires of white flowers just above the sumptuous foliage. As the Latin species name dioicus suggests, goastbeard is a dioecious plant, meaning that the flowers are either male or female, and are carried on separate plants. The males flowers, with their plumy stamens, are more showy than the females, but the females offer the added feature of pendulous seed heads that provide interest throughout the summer, and into the fall as they age to golden brown.

The Asian genus Rodgersia offers an array of tough, long-lived, magnificent foliage plants. All are rhizomatous, producing bulky underground running stems, so the strong, hairy petioles that carry the immense leaves emerge directly from the ground. The three species that have proven themselves at Plantations are aesculifolia, pinnata, and sambucifolia, all of which have thrived in the ground cover collection and at the Treman Woodland Walk. Rodgersia aesculifolia is the easiest to recognize, carrying palmately compound leaves with raggedly toothed margins that resemble the leaves of the horse chestnut tree. Flamboyant panicles of creamy white flowers create an impressive show in early summer.

Rodgersia pinnata produces impressively long, rugged, pinnately compound leaves, which, unlike the jaggedly toothed leaf margins of Rodgersia aesculifolia, have smooth rounded margins. Flowers are white, carried in plumy panicles that are smaller and less showy those of R. aesculifolia. Although the name pinnata would seem to indicate pinnately compound leaves, the terminal leaflets are instead often congested into a palmately compound cluster. This can sometimes make R. aesculifolia difficult to distinguish from R. pinnata, so remember to look at the leaf margins! A lovely R. pinnata selection is 'Superba' with rich pink flowers and coppery young foliage. It is slightly less vigorous than the more commonly seen white-flowered form, and curiously difficult to find in the nursery trade.

Rodgersia sambucifolia, as the name suggests, produces leaves reminiscent of the elderberry (Sambucus). It is similar to R. pinnata, but larger in size, and the large, oppositely and evenly paired light green leaves are held on reddish petioles that arch over towards the ground, rather than standing erect. Creamy flowers appear in late June and July, and compliment the olive-green foliage nicely. While Rodgersia aesculifolia and pinnata will rapidly form dense colonies of ground-covering leaves, R. sambucifolia is more content to sit in one spot, increasing the girth of its territory very slowly. All three prefer rich, moist soil in partial shade; they will be slightly tighter and smaller in full sun, but if kept moist, they will still grow well. All three Rodgersias are recommended as streamside plants, and they can indeed survive in boggy soil where they will just sit, rather than thriving or increasing in size.

Trachsystemon orientalis is a good plant for those fortunate gardeners with ample garden space. A member of the borage family, this robust spreader carpets the ground with large, ovate, bristly to hairy dark green leaves. It grows happily in shaded spots, but will do equally well in sun given adequate moisture. The individual flowers look like a larger version of borage blooms, with slender petals that are pointed rather than rounded. Clusters of these bright sky-blue blooms appear just as the leaves are beginning to emerge in May. Trachystemmon is not what you'd call a refined plant; its coarse rough-surfaced leaves are neither particularly elegant in shape nor complex in texture. It looks best when given a large space in which to roam, surrounded by other equally large-leafed plants. It also makes a bold ground cover that contrasts nicely with more finely textured golden or variegated shrubs, such as cutleaf golden elderberry (Sambucus racemosa 'Plumosa Aurea') or tricolor Japanese barberry (Berberis thunbergii 'Silver Mile').

Lastly there is the umbrella-leafed trio with the musical names of Astilboides, Darmera, and Diphylleia that hold their bold, round leaves aloft on a centrally placed petiole, producing the effect of a cluster of parasols. Like Rodgersia, all have underground stems, so the petiole, which holds the leaf aloft, rises directly from the ground. Upon close inspection, the three differ notably from one another, but all add a bold tropical ambiance to the garden.

The umbrella plant (Darmera peltata), a native of the northwestern United States, is reliably winter hardy and enjoys keeping its feet cool during our hot, humid summers. Although umbrella plants grow perfectly well in rich garden soil either in sun or shade, they are most content in locations where their thick underground stems can stay cool and moist, making them ideal candidates for streamside plantings. The pink flowers emerge before the leaves, rising on stalwart hairy petioles that emerge from the bare ground in spring. The flowers are followed by rounded, ruffle-edged leaves shaped like a slightly windblown inside-out parasol.

Shieldleaf (Astilboides tabularis) is the most majestic member of the umbrella trio. Its rounded leaves can reach more than two feet across and are held on stately three-foot-tall petioles. Shieldleaf's creamy flowers are carried in long, dense, slightly triangular plumes that drape gracefully forward from their own weight. This plant performs best in a moist, shaded location where its majestic leaves are protected from sun scorch. Although recommended for streamside planting, I have never known Astilboides to thrive or even persist for long in boggy conditions. A native of China and Korea, shieldleaf is perfectly winter hardy, although its emerging young leaves can be killed back by a hard late spring frost. To prevent early leaf emergence, select a site where the soil will remain cool into the spring, thereby encouraging plants to remain dormant until the danger of hard frosts has passed.

The last member of the trio carries the common name of umbrella leaf (Diphylleia cymosa). A native of the cool mountain woodlands of the southeastern United States, this plant is at home in humus-rich soil in partially shaded sites, where it gradually forms a colony of deeply and unevenly toothed, oval to rounded leaves. Diphylleia differs from the other two trio members in having petioles that fork near their apex; each arm of the fork bears a single leaf. This produces a dense, multi-layered effect that nicely sets off the small, rounded clusters of white flowers, which arch above the foliage in spring. A member of the barberry family, umbrella leaf offers the added ornamentation of attractive, blue, berry-like fruits that contrast markedly with the bright red stems that hold them.

With the hot, humid days of summer looming on the horizon, take some time out to visit the cool, shady ground cover collection at Plantations and enjoy all the fabulous foliage!