The Adaptation of Purple Sages

Native Environments

• Salvia dorrii inhabits areas of the American West that are cold in the winter and hot and dry in the summer. It grows at elevations from 960 to 9,800 feet where 7 to 15 inches of annual rainfall occur. Salvia leucophylla grows in California coastal sage scrub in the coast ranges of Southern California and Baja California from near sea level to 1,800 feet. Rainfall comes during mild winters, and summers are hot and dry. Garden sage is native to the Balkans and the area around the Mediterranean Sea, where there are mild cool wet winters and dry hot summers. All three species display adaptations to surviving limited rainfall and high temperatures.

Leaves

• Salvia leucophylla and Salvia dorrii have leaves covered with plant hairs, which help reduce water loss and reflect light, thereby lessening the heat load. Salvia leucophylla can also lose leaves during summer droughts, further reducing water loss. Salvia leucophylla grows two types of leaves, depending on the season. During winter, larger, thinner, softer leaves are present. In the summer, smaller, harder leaves appear. Leaves of garden sage are leathery and covered with plant hairs. Thickened hairy leaves of all the purple sages help reduce grazing as well.

Fragrance

• Fragrant foliage is a characteristic of most sages of the genus Salvia, and purple sages are no exception. The compounds responsible for the fragrances repel grazing animals and keep other plants from growing near them. In nature, Salvia leucophylla is encircled with a 5-meter-wide space where nothing grows and a further 8-meter band outside of that where grasses are stunted. S. leucophylla produces volatile compounds called terpenes that get dispersed in the air and soil surrounding the plant, with cineole and camphor being the most active agents, and they inhibit survival of other plants. Garden sage leaves contain 1 to 2.5 percent volatile oils, including camphor and cineole. Another constituent is thujone, a uterine stimulant that can be toxic if sage is eaten in large quantities. Salvia dorrii has aromatic leaves that have been used medicinally by native peoples.

Flowers

• All three purple sages have blue to lavender flowers produced in clusters that encircle the flower stalk. Flower clusters, or whorls, are spaced regularly along the stalk. Nectar is held at the bottom of tubular flowers that have an upper and lower lip. Flowers attract bees and day-flying sphinx moths. Floral adaptations position the pollen-bearing anthers so they touch the backs of bees that do the effective pollination.