Chamaebatiaria millefolium (Torr.) Maxim.

by Shelley Silva, Native Plants of Arizona 2004
Common names: fernbush, desert-sweet, tansy-bush (1, 3, 4, 5).
Family: Rosaceae (1).
Synonymy: Spirea millefolium (Torr), Sorbaria millefolium Focke, Basilima millefolium Greene, Chamaebatiaria glutinosa Rydb., and Spiraea glutinosa Fedde (6).
Etymology: Chamaebatiaria was named for its resemblance to Chamaebatia, with which it may share a common ancestor (6). Millefolium translates as “many-leaved,” or, literally, “with a thousand leaves” (7).

Identification
Growth form: Upright, densely branched, aromatic shrub; from 3 to 6 feet in height (3, 4, 5).
Roots: Minimum root depth of 12 inches (1).
Stem: When young, branches are viscid and pubescent, with simple and star-shaped hairs that are sharp-pointed or glandular-capitate (6). Bark is reddish-brown, becoming smooth and gray with age (3, 6). In addition, bark is characterized by prominent lenticels and distinct bundle scars (3).
Leaves: This shrub is characterized by its fernlike foliage. Leaves are grayish green, alternate, finely bipinnately compound; pubescent and sticky. From .5 to 3.2 inches in length. Leaves occur most densely near stem tip. Leaflet margins are minutely scalloped (4, 6).
Inflorescence/flowers: White, sticky, crinkly, 5-petaled flowers to 3/8 inch wide with numerous yellow stamens (4). Inflorescences are insect-pollinated and occur in racemes or panicles up to 4 inches in length at stem tip. Calyx is comprised of 5 persistent green sepals. Ovaries are superior and styles are free (6).
Fruit: Pubescent, leathery follicles have single carpels and few seeds. Follicles dehisce along the ventral suture and upper half of the dorsal suture (5, 6). Seeds are yellowish to brownish, linear to narrowly spindle-shaped, and slightly flattened at each end (6).
Similar species: Chamaebatiaria millefolium is the only species in its genus (6).

Ecology
Life history: Evergreen shrub (4).
Native/introduced: Endemic to the western United States (6).
Photosynthetic pathway:
Phenology: Flowers July to November (4).
Distribution: Arizona , Colorado , Utah ; west to California , northwest to Oregon , north to Wyoming (3). May be present as an early successional species on cinder cones and basalt lavas, but it also occurs on limestone and granite soils. It grows variously on rocky outcrops, in well-drained gravelly canyons, and on mountain slopes; from 4,500 to 8,000 feet (4, 6).

Uses
Cultivated ornamental due to its profuse inflorescences; extended flowering period; and fernlike, sweetly aromatic foliage (6). Occasionally browsed by deer, sheep, goats; only rarely by cattle (4, 6). Native Americans used a tea made from its leaves for stomachache (6).

References

1. Integrated Taxonomic Information System (ITIS) ( http://www.itis.usda.gov ).
2. USDA, NRCS. 2002. The PLANTS Database, Version 3.5. ( http://plants.usda.gov ). National Plant Data Center , Baton Rouge , Louisiana 70874-4490 USA .
3. Elmore, F. H. 1976. Shrubs and Trees of the Southwest Uplands. Southwest Parks and Monuments Association. Tucson , Arizona .
4. Epple, A. O. 1995. A Field Guide to the Plants of Arizona . Falcon Publishing. Helena , Montana. 5. Matthews, Robin F. 1994. Chamaebatiaria millefolium. In: Fire Effects Information System, [Online]. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory (Producer). Available: http://www.fs.fed.us/database/feis/ [2004, November 30].
6. Shaw, N. L. and Hurd, E. G. 2001. Chamaebatiaria millefolium (Porter) Maxim. fern bush, desert sweet. In: F.T. Bonner and R.G. Nisley, eds. Woody plant seed manual. AgricultureHandbook. U.S. Department of Agriculture, Forest Service, Washington , D.C. Available: http://wpsm.net/index.html . 6
7. Stearn, W. T. 2002. Stearn's Dictionary of Plant Names for Gardeners. Timber Press. Portland , Oregon .