Wildflower is published quarterly by the Wildflower Center. Its content is national in scope with articles about the conservation and use of native plants as well as news from the Wildflower Center. A subscription is provided to Wildflower Center members as a benefit of membership.
The shimmering beauty of silver plants is deceptive, for silvers are tough as nails. Found in harsh climates worldwide, these plants adapt to withstand extremes of heat, cold, drought, wind, salt, and sun. North America's frigid mountaintops, windy plains, rocky cliffs, deserts, and seacoasts have given rise to many silvers, from tiny alpine mats to grasses, flowering perennials, and towering evergreens.
While some require poor, excessively well-drained soil and fiercely exposed sites, many silver plants will thrive in the more benign conditions encountered in the garden.
Adaptations which allow the plants to conserve water in their tissues are responsible for the silvery appearance, whether grey-green, silvery-blue, or pure, gleaming silver. Downy silvers such as the native Western sagebrushes (Artemisia spp.) and leadplant (Amorpha canescens) of the Great Plains have leaves, and sometimes stems, covered with fine hairs that reflect sunlight and maintain a layer of high humidity near the leaf surface. Although green in reality, these appear silver in varying degrees, depending on length, angle and density of hairs, and on the season, latitude, and exposure.
The underlying green of waxy silvers, including some yuccas, grasses, and blue spruce (Picea pungens) is protected by a waxy or powdery coating that prevents excessive evaporation. Sun-loving downy and waxy silvers become more silvery the more sun they get. They require good drainage and air circulation and only a few, like the shrub dusty zenobia (Zenobia pulverulenta) with silver-backed leaves and some willows (Salix spp.), prefer moist soil.
The less-familiar variegated silvers are usually woodland plants thriving in shade and richer soil. These include the variably silver-marked Southeastern heucheras (Heuchera cylindrica, H. sanguinea, and H. americana) and native gingers like Hexastylis minor in the eastern Piedmont and the California endemic Asarum hartwegii.
Not surprisingly, many of our native silvers are endemic to hot places in the South and West. Silver plants may have additional qualities beneficial to survival. Types of agave, for example, employ succulence to store water, and the reduced leaf surface of plants like the Southwest's Lupinus sericeus with its curled leaves or Dalea greggii with its small leaves limits evaporation. The Southeast's saw palmetto (Serenoa repens) features tough, leathery leaves that help it retain water. Others contain bitter sap or sharp scents like tall blue rabbitbrush (Ericameria nauseosa ssp. nauseosa var. speciosa) or spines like rattlesnake master (Eryngium yuccifolium). These make most silver plants unpalatable to prey.