Hardy Cyclamen for the Home Garden

During the holidays, many decorative houseplants appear in garden centers and then grace our homes with flowers and foliage to celebrate the season. Amongst the familiar poinsettias (Euphorbia pulcherrima), Christmas cactus (Schlumbergera spp.), amaryllis (Hippeastrum spp.), and paperwhites (Narcissus papyraceus), and more exotic gardenias (Gardenia jasminoides), bromeliads (family Bromeliaceae), anthuriums (Anthurium spp.), and orchids (family Orchidaceae), the florist's or Persian cyclamen (Cyclamen persicum) stands out for its elegant flowers, delicate fragrance, and gorgeous variegated foliage. The standard-sized varieties, with flowers in shades of bright red, pink, magenta, or white, and the "teacup" varieties bred for smaller size, are well-suited to cool or even chilly indoor temperatures (such as a spare bedroom), but they will not survive outdoors in our winter climate.

Fortunately, there are some other cyclamen species that are decidedly more cold-hardy and can thrive in a temperate Pennsylvania garden. Almost all species in the genus Cyclamen, roughly two dozen or so, are native to regions surrounding the Mediterranean basin, growing in well-drained, rocky, forested sites and a climate with hot, dry summers and cool, damp winters.

Botany

Cyclamen grow from perennial tuberous stems (also called tubers) that are generally spherical or flattened in shape (think of a peach and a donut peach), depending on species. In botanical parlance, they are "subglobose," which means almost or nearly round. Although you may see cyclamen referred to as corms, another type of bulb-like structure, they are not corms. Corms and tuberous stems have very different life cycles. A corm, such as a crocus, is used up in each growing season to produce a new corm and small offsets (baby corms), whereas the cyclamen's tuberous stem is perennial and can be very long-lived. It does not produce baby tubers, but it does continue to expand in size, producing new leaves, flowers, and roots from growing points on the tuber each year. The tubers of some species can become over a foot in width, producing hundreds of flowers in a season. Tubers can live for 30 years or more.

The genus name, Cyclamen, comes from the Greek word "kyklos," which means circle, referring not only to the rounded tuber but also to the intriguing habit of some species' flower stalks to spiral into a coil after flowering, ensuring that the seed capsule gets close to the soil before dispersing its seeds. In Europe, the common name often used for this elegant plant is sowbread or swinebread, from the apparent relish with which pigs hunt for and eat the tubers. Although cyclamen is mildly toxic to humans, pets, and horses if eaten, that does not seem to deter deer from browsing or small rodents from digging and eating tubers.

Cyclamen's lovely flowers are borne singly on slender stalks arising from the plant's tuberous stem. The bud is downward-pointing and tightly spiraled; when it opens, the five petals reflex upward, often slightly twisted. Cyclamen flowers perched above the foliage look like a cluster of delicate butterfly wings and often carry a hint of sweet fragrance. The dark green foliage ranges from rounded, heart-shaped to longer, lance-shaped blades, often marked with striking patterns of silver, gray, or lighter green; the underside of the leaves in some species is purplish to red.

Propagation is generally from seed, as it is difficult to divide the tuberous stem successfully without damaging it. Because of this, there is a great deal of natural variation in the resulting seed-grown plants, even within named cultivars. Harvesting of tubers from the wild for the horticultural trade has led to a decline in native populations of some species to the point of  being endangered, so it is best to purchase tubers or seeds from reputable nursery-grown sources.

Garden Culture

Cyclamen do best in shade or woodland gardens, under the canopy of deciduous trees, shrubs, or hedges, in slightly alkaline soil that is both well-drained and moisture-retentive. They tolerate drought and dry shade conditions well, and they can live for many years. Once established, leave the planting area undisturbed to allow the tubers to increase in size and self-sown seedlings to mature, forming a lovely drift over time. Small seedling tubers can be carefully lifted and replanted to prevent overcrowding.

Growing cyclamen successfully in our climate means making sure they have excellent soil drainage throughout the year, with adequate moisture during fall, winter, and spring, followed by drier conditions during the summer, when the tubers are dormant. Incorporate good-quality organic matter, such as compost or leaf mold, into the soil before planting to ensure both good drainage and moisture retention.

Because of their small stature and their summer dormancy, cyclamen can easily be smothered by larger, faster-growing perennials or annuals that need consistent watering during the summer months. It is best to grow cyclamen on their own or with other well-behaved, dry shade perennials, such as native sedges (Carex spp.), small hostas (Hosta spp.), and small ferns. Use only a thin layer of mulch, such as leaf mulch or wood chips, over the planting area.

Tubers should be planted when dormant; late summer is a good time for planting. Be sure that the dormant tubers are plump, not shriveled or desiccated. Plant them shallowly, only about one inch or less in depth, in loose, rich soil, and cover them lightly with a thin layer of soil or leaf mulch. Once established, they will eventually find their own depth. Standing water, either in the soil or on top of the tubers, can lead to tuber rot and death of the plant.

Hardy Species for Pennsylvania

Two of the hardiest species of cyclamen, and the most readily available in the horticultural trade, are Cyclamen hederifolium, commonly called hardy or ivy-leaved cyclamen, and Cyclamen coum, commonly called Persian violet. Both are considered cold-tolerant in USDA Plant Hardiness Zones 5-7, but because their tubers grow close to or even exposed at the soil surface, a light mulch of leaves or evergreen boughs during the winter is beneficial. A blanket of snow does not hurt the foliage or flowers and acts as a good insulator, but is not always reliably present in Pennsylvania.

Hardy cyclamen (C. hederifolium) blooms from late summer to early fall in shades of pink or white on stems about 3 to 6 inches in height. The leaves are highly variable in shape, from rounded to ivy-shaped, in color, from dark to grayish-green, and in surface markings. The foliage appears either with the emerging flowers or follows a month or so later, and then persists through the winter until finally going dormant by early summer.

Persian violet (C. coum) blooms in late winter or early spring. Generally smaller in stature than hardy cyclamen, it produces new flowers and foliage buds in the fall, with foliage appearing first, followed by flowers on 4 to 5-inch stems in early spring. Both foliage and flowers fade into dormancy by early summer. The leaves are rounded to heart-shaped, dark green on top, either plain or with silvery markings, and dull crimson underneath; flowers are magenta, pink, or white, splotched with purple at the base of each petal.