Following on from the “everything is flowering a month ahead of schedule” pattern of the past few months, June 2015 looks to be lock-step, so the discussion here will be of summer flowers. Given the heat and lack of rain our summers bring, there is increasing interest in plants that tolerate these conditions, and a tour around the E.H. Lohbrunner Alpine Garden is an excellent place to see plants that fit these criteria. Among the best heat and drought tolerant, summer flowering plants we can grow are species and hybrids of the genus Cistus. Known as rockroses, they are aromatic evergreen shrubs native to northwestern Africa and southwestern Europe. Cistus are not roses; however, they do grow on rocky slopes, exposed to the full glare of the Mediterranean sun and have flowers that are not unlike those of single roses. Not surprisingly, most cistus are excellent candidates for “xeriscape gardens,” where plants are supplied with a minimum of irrigation. Three of the toughest rockroses are described below.
Cistus albidus, the grey-leaved cistus, is named for the pale hairs (albidus = whitish) that clothe all parts of this robust plant, but the main attraction is the 5-cm-diameter bright, lavender pink flowers at the tips of the branches. Cistus albidus is 1.2-m-tall shrub, located on the lower path in the African section of the Alpine Garden. Note that the flowers look crumpled. Almost directly across the path is a very different looking cistus—C. × lenis ‘Grayswood Pink’. This rockrose is more of a groundcover, growing only to about 30 cm tall, but spreading and rooting over a large area. The youngest stems are reddish, as are the flower buds, and the 4-cm flowers are silvery pink, each petal slightly darker at the tip and fading to white at the base. Whereas most rockroses flower sporadically over the summer, ‘Grayswood Pink’ produces prodigious quantities of flowers over the season. Perhaps the most distinctive of the Garden’s rockroses is C. laurifolius. Laurel-leaved cistus is an open, upright bush, 1 to 2 m tall, with resinous stems and dark, almost black-green leaves. The white flowers are 4 to 5 cm across, emerging reddish buds. This cistus is located in the European woodland, directly behind the rammed earth wall on the north side of the Roseline Sturdy Amphitheatre.
To view examples of the plants mentioned visit our forums.
Article submitted by Douglas Justice, Associate Director, Horticulture and Collections, May 31, 2015.Forum photos posted by Wendy Cutler.