Rare Houston Camphor Daisy
Mercer Botanic Gardens is one of 38 leading botanical gardens and arboreta in the United States that collectively maintains over 750 species for the Center for Plant Conservation’s (CPC) National Collection of Endangered Plants. The CPC preserves rare, native (American) plants in a centralized network of botanical institutions within 17 states and the Virgin Islands. In Texas, Mercer Arboretum & Botanic Gardens, San Antonio Botanic Gardens, and The Lady Bird Johnson Wildflower Center share the responsibility for the preservation of rare plants within seed banks or as live specimens. In addition to the CPC institutions mentioned above, The Arboretum at Flagstaff and the Desert Botanical Garden of Arizona maintain the rare mountain and desert species for Texas. To preserve the nation’s rare botanical treasures, Mercer and the CPC’s other member institutions hold partnerships with concerned citizens, private and government conservation organizations, universities, and colleges.
The CPC assigned Mercer the maintenance of the Houston Camphor Daisy in 1996. The unique prairie habitat that the Houston camphor daisy thrives in is vulnerable to development as well as invasive species, namely the Chinese tallow tree. Prior to development, periodic natural fires and ranging herds of bison reduced competition from other plants and maintained open prairie habitats. Historically, the Houston camphor daisy occurs on “pimple mounds” or “mima mounds,” or natural bare spots in the native coastal prairies. Today, periodic mowing, carefully managed cattle grazing, and prescribed burns help to maintain prairie habitats. This tap-rooted annual grows to 20 inches tall and has branched stems that bear elongated, smooth-edged or sparsely-toothed, one to two inch long leaves. The Latin word “aurea” used to describe Rayjacksonia aurea denotes the golden-yellow color of the ray and disc flowers. The bright yellow heads of the Houston camphor daisy grow to just over one-half inches across and cover the plants in the fall.
Composed of approximately 25,000 members, the Asteraceae family is also called the composite, sunflower, or daisy family and occurs worldwide, except in Antarctica. With approximately 620 species recorded in Texas, the Asteraceae family is one of the largest families of plants in Texas.
In the composite family, blooms are typically arranged as a “head” composed of many small flowers attached to a base also known as the “receptacle.” In many composites, including the Houston camphor daisy, the outer or marginal flowers of the head have a single, showy, petal-like strap and are referred to as “ray flowers.” The interior, tube-shaped flowers are called the “disc flowers.” The “petal” of a daisy is actually a petal-like strap from one individual ray flower. The ray flowers form a circle at the outer margin of the daisy’s head and the many disc flowers form the center of the head. Common garden favorites including sunflowers, asters, and daisies are composites that often display the ray and disc flower arrangement shown by Rayjacksonia.
In addition to ornamental merits, the Asteraceae family provides important food sources: sunflowers (Helianthus, a crop native to America), lettuce (Lactuca), artichoke (Cynara), safflower (Carthamus), salsify (Tragopogon), chicory and endive (Cichorium). Other Asteraceae plants of economic importance include the Chrysanthemum coccineum, which provide the insecticide pyrethrum, and red dye safflower (Carthamus tinctoria).
In the Asteraceae family, the single seed produced from a fertile flower is enclosed within a dry, thin-shelled fruit named an “achene” or “cypsela.” The fruits produced by the ray and disc flowers are crowded within each head of a Houston camphor daisy. Sunflower seeds are popular examples of the fruits formed by members of the composite family.
The three annual herbs identified as Rayjacksonia, Houston camphor daisy, viscid camphor daisy and Gulf coast camphor daisy, occur only in North America. All three display yellow flowers and emit an aromatic camphor-like odor that reportedly repels browsing deer. The viscid and Gulf Coast camphor daisies occur in the Rio Grande and Gulf Coastal Plains, and extend into the central and southern states and Mexico. The rare Rayjacksonia aurea, however, occurs only in Harris and Galveston counties as a pioneer plant of barren soils.
The Houston camphor daisy is often associated with the rare Texas windmill grass (Chloris texensis) and prairie dawn (Hymenoxys texana), which Mercer also maintains for the National Collection of Endangered Plants. These three plants are endemic (native) to the coastal plain of southeast Texas, and are part of over 300 plants that are endemic to Texas and found nowhere else on Earth. Texas supports a vast diversity of butterflies, birds, and other wildlife that migrate through and inhabit the state’s prairies. The wildlife is directly dependent upon the nectar, forage, and seed provided by Texas prairie wildflowers and grasses.
Conservation volunteers, partners, local botanists including Dr. Larry E. Brown of the Houston Community College and Spring Branch Science Center, and biologists with the Texas Parks and Wildlife Department, Harris County Flood Control District, the U.S. Fish and Wildlife Service and the U.S. Army Corps of Engineers monitor local wild populations of Rayjacksonia aurea as well as other rare Harris County species for the Texas Natural Diversity Database Program. These volunteers and partners also help collect seed stock for the CPC National Collection of Endangered Plants. The Texas Natural Diversity Database Program is a member of NatureServe, an international network of natural heritage programs and conservation data centers found in all 50 U.S. states, Canada, Latin America and the Caribbean.
In addition to the rare Houston camphor daisy and prairie dawn, 76 other rare wildflowers in the family Asteraceae remain on the Texas rare plant watch list and include other species maintained by Mercer for the National Collection of Endangered Plants: white fire-wheel (Gaillardia aestivalis var. winkleri); rough-stem aster (Symphyotrichum puniceum var. scabricaule); slender gay feather (Liatris tenuis); and bog coneflower (Rudbeckia scabrifolia). The rare Houston camphor daisy typically blooms from late September through December and is displayed with other rare Texas plants in Mercer’s Endangered Species Garden that was awarded the Best of Backyard Habitats by Texas Parks and Wildlife and the National Wildlife Federation in 2004, and certified as a butterfly garden by the North American Butterfly Association in 2009. The Endangered Species Garden serves as an educational tool for the importance of “wildscaping,” demonstrating the use of permanent water and food sources, composting, and organic management methods to benefit wildlife. Common native plants complement the rare species in this display garden and provide examples for home landscapes.
In 2005, the Houston Camphor Daisy received full sponsorship for the CPC through generous donations from Anita Tiller in memory of Michael H. Tiller, Aveda Cosmetics, Crouch Environmental Services, Inc., Lakewood Forest Garden Club, and Suzzanne Chapman in honor of Blanca and William Othon. The Houston camphor daisy benefits from annual sponsorship stipends directed to Mercer for travel costs to collect seeds, equipment and supplies for the plant’s recovery.
Adapted from Parkscape, Fall 2001
Harris County Precinct 4
Anita A. Tiller, Botanist
Mercer Botanic Gardens
Photo by Suzzanne Chapman
Updated February 29, 2012
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