A morning stroll in my woodland front yard with a garden writer elicited this response:
“Is it real?” she asked. “Touch it,” I implored. “Oh my God! It’s like a leather mushroom!” came the squealing reply. Beads of dew trickled off the oddly mottled leaves, while I pointed to the botanical zoo around her, “Welcome to the wonderful world of Podophyllum.”
Podophyllum is an odd genus of herbs in the barberry family (Berberidaceae). Known as Dysosma in early texts, Podophyllum is joined by barrenwort (Epimedium), inside-out flower (Vancouveria), and vanilla-leaf (Achlys) as herbaceous members of that otherwise mostly woody family. The bizarre, oddly marked leaves look like they belong on an old Star Trek set rather than in the woodland garden, but they definitely catch your eye. Dan Hinkley (another podophyllumophile) considers them, “among the most dramatic foliage plants that I currently have in my garden.” Both he and I have seen them in China and Japan, where they are revered for their striking properties. The genus is composed of one rampant herbaceous species from the eastern half of North America and five species that range from the mixed forest areas of China’s northwestern Yunnan Province to rhododendron-thick, mountainous areas of India; other species have been described, but the taxonomy remains unresolved. Most of the Asian species hail from high elevations (up to 12,000 feet), which imbues them with a fair degree of hardiness.
Only these six species and two (of the many) cultivars have made it into general, albeit limited, distribution. American mayapple (Podophyllum peltatum) is the rampant grower from our Eastern woodlands, with glossy, fleshy, umbrella-like leaves and white flowers. Podophyllum difforme has leathery, incredibly odd, rectangular leaves overlain with a dizzying array of black, silver, and green patterns atop a bronze or khaki base color. Podophyllum delavayi sports thick, snowflake-like leaves with light and darker bronze bands. Podophyllum hexandrum (syn. P. emodii) includes several variants such as ‘Majus’, a dependable, mottled form with serrate maple-like leaves that fade by midsummer. Podophyllum pleianthum may be considered the “big daddy” of the genus, with flat, hexagonal disk-like leaves of shiny green that can be twenty inches across. Podophyllum versipelle is similar, with somewhat smaller, more lobed leaves. Dan Hinkley released an array of hybrids between the last two species through his Heronswood Nursery. Terra Nova Nurseries has done extensive breeding between most of the species; ‘Kaleidoscope’, with its hexagonal, brilliantly marked leaves, and ‘Spotty Dotty’, a vigorous, low-growing form with mottled leaves, have been successfully put into tissue culture and are now in general distribution.
Emerging early in spring, podophyllums occupy a bold-leaved niche shared by Hosta, Astilboides, and Rodgersia. They are wonderful when combined with lacy accent plants like Tiarella and Disporum. The leaves have a substance similar to the thickest hosta leaves, with a color palette from khaki to deep green marked by splashes of burgundy, black, and white. Flower colors range from white to deep burgundy, on waxy blossoms that are sometimes hidden beneath the foliage. The flowers are notable for their odor; being fly-pollinated, they often smell like rotten cheese—or worse. The fruits are usually egg-shaped and about two inches long, varying in color from green to bright red; they are eaten by mammals, turtles, and birds, all of whom distribute the seeds by special delivery. Though somewhat drought- and sun-tolerant, most podophyllums are happier with an evenly moist location and deep shade; their American cousin will tolerate full sun if the soil is dependably moist. Watch the leaves of any species for sunburn, an indicator of too much direct sunlight.
In the current pharmacopiaea, there is interest in podophyllotoxin, a resin-like substance obtained from podophyllum rhizomes, for use in tumor and cancer reduction (including genital warts and some HIV complications like leucoplakia); it is also used in anti-scarring creams. In the early twentieth century, the resin was the principle ingredient in Carter’s Little Liver Pills. Indian shamans mixed the rhizome with cannabis and used the concoction to put their victims into a “spirit state.” (Do not try this at home, as it is quite poisonous!) Podophyllum resin has been used in Native American cultures as a powerful laxative, and young shoots were eaten to commit a speedy suicide. The fruit is the only edible part of the plant, but only when fully ripe; it has a sub-acid taste and a texture like an unripe strawberry (so why bother?).
While the American mayapple is hardy in USDA hardiness zones 3 to 8, its Asian counterparts can usually only be trusted in zones 6 to 9. Podophyllum hexandrum can, indeed, be considered one zone hardier (zone 5A), having been grown successfully in Palmer, Alaska. From personal experience, the plants with hybrid blood, especially with P. delavayii (such as ‘Spotty Dotty’) tend to be more vigorous and hardier. Hybrids with P. difforme (‘Kaleidoscope’) require a more protected position in the garden. I have seen new shoots tolerate mild frosts in the spring, but threats in the low 20s F may require covering the plants with some type of frost cloth for protection. I have also used large, inverted plastic containers to provide a few degrees of protection.
American mayapple is fond of moist areas, and I have seen colonies thriving near a boggy area. The Asian species like a rich, moist soil, preferably acidic; while somewhat tolerant of drought, leaves will crisp along the edges or, in extreme cases, the plants will go dormant until the following spring.
Soil and Fertilizer
Soils with a pH of 5.8 to 6.3 (somewhat acidic) are ideal, with the characteristics of woodland loam (highly porous with no chance of compaction). This can be achieved in containers with a fifty-fifty mixture of peat or compost and pumice or perlite.
Too much chemical fertilizer can bring on leaf burn. These are slow-growing plants that cannot be pushed. While I have seen some great plants grown with time-release fertilizer, it must be experimented with for best results. Organics are preferable, especially compost tea or half-strength fish emulsion; foliar sprays of either can produce great results. Marietta and Ernie O’Byrne, of Northwest Garden Nursery in Eugene, Oregon, have received plugs of podophyllum and grown them to large plants in a single season using only compost tea. Like hosta, podophyllums do require two to three years to “settle in.” Most of the Asian selections will gently colonize.
Maintenance and Pests
Podophyllums are remarkably carefree plants. Watch for spring frosts and protect plants if necessary. They require no pruning, and the first killing frost will knock them to the ground. In mild areas like California’s Central Coast and the Bay Area, foliage may persist well into winter. It should be removed in spring when the shiny, mushroom-like new growth begins to emerge. Snails and slugs may take an occasional nip, but they tend to dislike these plants.
While the wider distribution of podophyllums has been made possible by the advent of tissue culture, most can be propagated from sections of the rhizome, each with a visible eye. I have seen colonies of small plants sprout from pieces left after transplanting a large specimen. The seeds are large and quite viable. They require a warm, moist period for a month, followed by moist stratification (wet-chill)—similar to the conditions for germinating hellebore seeds. This can be done in a refrigerator (for about two months), after washing the seeds and placing them in a squeezed-dry ball of sphagnum moss. Once chilled in this method, the seeds can be sown without cover. Germination is erratic and has taken as long as five months). Keep a plastic bag over the pots of seeds or seedlings to prevent them from drying out.
At Terra Nova Nurseries, we have successfully hybridized a number of species of Podophyllum, even crossing the American and Asian species. Most podophyllums are self-incompatible; if you want seeds, try to have several clones or species nearby. Pollinating is an easy task as flowers are quite large. Pick the fruit only when it softens, and wash it thoroughly.
Podophyllum offers a peek into another world of bold foliage plants. Will one sneak into your garden?