Scientific name: Jamesia americana Torr. & A. Gray

Common names: waxflower, cliffbush

Family: Hydrangeaceae

Article by Noah Gapsis, SFBG Horticulturist

On the sheer cliffs and shaded, rocky slopes of our southern Rocky Mountains, one of the most attractive native shrubs resides in relative obscurity. Jamesia americana – commonly known as waxflower, or cliffbush – is a charismatic member of the hydrangea family, one of the few endemic to North America.

(c) Suzanne Dingwell, (CC BY-NC), https://www.inaturalist.org/observations/121963660

Jamesia americana is a deciduous shrub, generally between 3-8 feet tall, though occasionally taller and much wider. The bark of the shrub exfoliates in papery strips, revealing a cinnamon-colored underlayer, similar to ninebark or mock orange. The opposite leaves are broad and bright green; they bear downy, white hairs and coarsely serrated margins. The delicate flowers, which mostly appear in terminal panicles late spring through summer, are white or pinkish, radially symmetrical, and mildly fragrant. In the fall the foliage turns deep orange-red.

© Aaron Sidder, https://www.inaturalist.org/observations/50163462

Waxflower prefers well-drained, rocky sites, often clinging to canyon walls or found on rocky slopes in forest openings. However, despite this overall preference, its distribution and habitat is dependent on its discrete subspecies. Four are currently recognized, each distinguished by subtle differences in morphology and geography. Jamesia americana subsp. americana, the nominate form, is widespread through much of the species’ range. This is the one most commonly found in New Mexico and Colorado, which frequents stream banks and forested canyon bottoms as much as rocky slopes and cliffs. Jamesia americana subsp. rosea is restricted to the Sierra Nevada in California and the Great Basin in Nevada; it has, as the name suggests, notably pink flowers. Jamesia americana subsp. macrocalyx is endemic to several counties in Utah. The most geographically distinct, J. americana subsp. zionis, is found only in Zion National Park and the surrounding canyons, growing at much lower elevations on sandstone and slickrock, often with visible moisture. While these distinctions are subtle and sometimes overlapping, they reflect the ecological diversity and geographic isolation of the mountain West, where small differences in elevation and substrate can give rise to localized plant forms. These forms, of course, tend to overlap and intergrade, further complicating identification. Since the subspecies present in New Mexico is the “typical variety,” however, we just call it Jamesia americana.

The genus Jamesia was named for its collector, Edwin P. James (1797-1861), an American physician and geologist who joined the Long expedition to the Rocky Mountains in 1820 – the first federally sponsored scientific expedition to explore the West.  He brought hundreds of collections back and recorded many species new to classification; one was a poor specimen,a woody stem with terminal flowers, without notes or information, likely from the canyon walls at the mouth of the South Platte River. In 1840, Harvard Professors Torrey and Gray assigned it to a brand new genus, Jamesia. The next collection of Jamesia, after being named as such, was made right here in Santa Fe in 1847 by Augustus Fendler.

from A Taxonomic Study of Jamesia, Noel and Patricia Holmgren.

The plant of course has a much longer history than that. Paleobotanists have identified fossils dating to the Oligocene in the fossil beds in southwestern Colorado, which appear to belong to an extinct species of Jamesia. The morphology of the leaves are, in fact, a good match for the shrub in its modern-day incarnation. It likely originated at the same time as many of our other distinctive native shrubs – such as fernbush and Apache plume – living and spreading out through the geological and climatic upheavals that made the landscape as we know it today. 

Although its evolutionary history is complex and mysterious, cliffbush has been in cultivation almost since it became known to science. It was introduced to Kew Gardens in 1862 and featured in the 1875 issue of Curtis Botanical Magazine –  a time when exotic species, especially from the American wilderness, were the rage in Europe. Far before that indigenous peoples likely used the plant for food and/or medicine. According to one ethnobotanical index, the Chiricahua Apache and Mescalero Apache ate the fresh seeds. It helps sustain native pollinators – the flowers are primarily pollinated by native bees and insects, but sometimes hummingbirds also visit. For all these reasons, it is a great addition to local gardens, especially as a replacement for more water-needy shrubs for the shade that don’t support our local food web.

© User upthemountain, https://www.inaturalist.org/observations/243745467

Waxflower is a great selection for dry shade and part-shade in Santa Fe gardens. It does appreciate some water to look its best – though far less than introduced options, such as Euonymus or Viburnum. It also appreciates protection from summer-hot afternoon sun. Jamesia americana (by which I mean subsp. americana, the one in nurseries) is really from a mountain habitat, like the slopes of the Sangre de Cristo, so an approximation of that – a opening among larger trees or shady, sloping corner – allows it to thrive and look its best. In fact, one taxonomist surmises that its patchy native range is in fact due its need for cold moist air that comes down from higher up mountain slopes in dry summers. So, when you see it clambering over a large rock, whether a trailside cliff or in a well-planned garden, be thankful you can enjoy its unique beauty, toughness, and legacy tied to early botanical exploration. 

References