What’s Blooming 9/14/2015
By: | 09/14/2015
Summers in the Treasure Valley are bookended by the yellow flowers of two of our most abundant native shrubs. In late spring, bitterbrush bursts into bloom and gives the foothills a creamy yellow hue. As summer comes to a close, the foothills turn yellow-gold with the flowers of rabbitbrush. With the rabbitbrush now beginning to bloom, it is clear that fall is imminent.
The two most common species of rabbitbrush in our region are gray rabbitbrush and green rabbitbrush. Both are in the sunflower family (Asteraceae) and are related to a couple of other well-known late summer/fall flowering genera, Aster and Chrysanthemum. Gray rabbitbrush (Ericameria nauseosa), also known as rubber rabbitbrush, is a densely branched shrub that reaches an average height of 3 feet. Leaves are narrow and numerous, and stems and leaves are covered in short, white, felt-like hairs giving the plant a gray appearance.
Many plants in the sunflower family have inflorescences that are a combination of ray and disk flowers clustered tightly together and arranged in such a way that the inflorescence appears as a single flower. Consider sunflowers, for example. What appear as petals around the outside of a sunflower are actually a series of individual flowers called ray flowers. In the center of a sunflower are dozens of disk flowers. The flowers of gray rabbitbrush lack ray flowers, and instead are clusters of 5 or so disc flowers. The flower clusters form at the tips of each branch. When the plant is in full bloom, the flowers create a sheet of yellow-gold atop white-gray foliage – a sight to behold.
Native Americans used the flexible branches of gray rabbitbrush to weave baskets and the flowers to make dyes. The stems contain a latex sap (which explains the common name, rubber rabbitbrush). Native Americans would occasionally chew the stems to help relieve hunger and thirst. A tea was made from the stems to treat coughs, colds, chest pains, and toothaches, and bundles of branches were burned to smoke animal hides.
Green rabbitbrush (Chrysothamnus viscidiflorus) is typically smaller than gray rabbitbrush, reaching a maximum height of about 3 feet. Its stems and leaves appear similar to gray rabbitbrush except they lack the dense, white hairs. The stems and leaves also have a stickiness to them, and the leaves are often twisted or curled. The flowers are clusters of 5 or so disc flowers (again, no ray flowers) that form at the tips of the branches. Both species of rabbitbrush are commonly found together in nature, and so growing together in a garden setting they look right at home.
All of our native shrubs have ornamental potential, but rabbitbrush is particularly high on that list. It provides year-round interest and can be easily maintained in an attractive form simply by cutting it back by a third or more each spring. If it becomes too large and gangly, it can be cut back nearly to the ground and will regenerate, quickly returning to a more manageable form. Its vibrant, yellow, late summer flowers complement those of goldenrod and help ring in the harvest season.
You can witness both species of rabbitbrush in full bloom this fall by visiting Idaho Botanical Garden and strolling through both the Idaho Native Plant Garden and the Lewis and Clark Native Plant Garden.