Erigeron L. Fleabanes (Achaetogeron, Darwiniothamnus, Ioeasperma, Pappochroma, Stenactis, Trimorpha)
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Erigeron L. Fleabanes (Achaetogeron, Darwiniothamnus, Ioeasperma, Pappochroma, Stenactis, Trimorpha) Other Common Names: Daises, Summer Starwort. Family: Asteraceae (Compositae). Cold Hardiness: With so many species and mostly hybrids among them available in the trade, it is not surprising that reported cold hardiness is highly variable among authorities for this genus; taxa can be found that are cold hardy as far north as USDA zone 2, while others are perennial only in cold to USDA zone 8; with proper cul- tivar selection, Fleabanes can be grown in virtually any region from USDA zones 2 to 11. Foliage: Foliage varies from deciduous (dieback), semi-evergreen, to evergreen depending upon the species and site conditions; the alternate simple leaves range from 1O to 4O (6O) long, some basal leaves are longer on var- ious taxa; tips of most taxa are acute to acuminate, while a few species are nearly rounded to spatulate; bases are variously acute angled to cuneate, sometimes with winged petioles; margins are often ciliate and may vary from entire to toothed or even shallowly lobed, petioles are usually short with upper leaves often sessile. Flower: Heads are usually small, 1O to 1½O (2O) diameter composite inflorescences with tiny button or disc-like center of disk florets surrounded by two or more rows of ray flowers with slender lanceolate to strap-like petals forming a ring around the disk flowers; the ray flowers of Erigeron spp. are typically narrower than those of most Aster spp.; ray flowers are lacking in a few Erigeron spp.; ray flowers are variably white, pink, purple, or bluish purple among the various taxa, while the disk flowers are usually yellow or yellow-green in color; the composite flowers may be borne singularly, as in most of our regionally native species, or in loose corymbose inflorescences; most of the current cultivars in the trade are spring bloomers in our region, often declining or dying as summer approaches, while several of the native species will bloom whenever temperatures permit. Fruit: Composite clusters of small achenes follow flowering, which are by and large flattened and two or three ribbed; the pappus may be absent or in rows of fragile capillary bristles aiding in wind dispersion; plants will appear tidier if old inflorescences are periodically deadheaded. Stem / Bark: Stems — most produce erect and well branched stems, while a few form compressed rosettes; most are green to red in color and hairy pubescent; Buds — buds are tiny, foliose, pubescent, and green or red in color; Bark — not applicable, as nearly all Erigeron are herbaceous. Habit: Fleabanes are typically annual, biennial, or herbaceous perennial plants; many of the perennial taxa go dor- mant in winter while others may be semi-evergreen to evergreen in mild climates; most species develop spreading irregular mounds of well branched stems with most species maturing at 12O to 24O (36O) tall and may be found in colonies of indefinite spread; a few species have a more procumbent habits as the result of more rosette-like stems and these species are more likely to form denser colonies; overall fine to medium- fine textures would be attributed to most Erigeron; in the wild, many species are found growing intermixed with other meadow or roadside weeds. Cultural Requirements: With the numerous species and hybrids represented in this genus, it is difficult to make too broad of generalizations, however most taxa can be grown in full to partial shade and require at least moderately well drained soils; most will tolerate a variety of soil pH levels; otherwise species vary dramatically in there tolerances to cold, heat, drought, and salinity exposures; most species can be propagated easily, ei- ther from seed or vegetatively. Pathological Problems: Mildews, leaf spots, fungal rusts, and aphid infestations have been reported, but few are consistently a problem in landscape settings. Ornamental Assets: Erigeron offer charming soft textured daisy-like flowers over an extended blooming time and an ability to last for several days as cut flowers; minimal inputs are required to grow Fleabanes; some taxa of- fer a high degree of salinity tolerance. Limitations & Liabilities: Limited heat tolerance in most commonly available cultivars tends to confine them to spring use in our region; lodging of taller forms may occur under vigorous growth conditions due to the weak stems of some taxa. Landscape Utilization: While members of this genus are most commonly encountered as roadside or meadow weeds or wildflowers, several cultivars are popular in Europe and to a more limited extent in the United States for their cheery spring flowers; cultivated Erigeron are most commonly grown in mixed or perennial borders, but may be found in wildflower plantings or grown as cut flowers in residential gardens. Other Comments: The common name of fleabane is attributed to various origins, including the scent of some spe- cies when dried which according to legend repels fleas, conversely according to others it is the general re- semblance of the seeds to fleas that gives Erigeron its common name; the genus name is derived from the Greek words eri meaning early and geron meaning old man, in reference to the quick presence of whitish hairs on either the fruit or stems as they develop; this genus has been somewhat neglected in the U.S. trade, perhaps due to the presence of so many native taxa reducing its novelty; this is a highly confusing group tax- onomically and even the noted botanists Correll and Johnston (1979) lament the genus' similarity to a number of other similar daisy-like composites. Native Habitat: This genus has a cosmopolitan distribution throughout both Hemispheres, with the greatest spe- cies diversity in North America; numerous species are native to Texas. Related Taxa: About 150 to 175 species of Erigeron are native to North America with a similarly large number na- tive to the other regions of the world, but only a handful of taxa are found commercially in the trade; many of the commercial cultivars are sold under then species name Erigeron × hybridus Hieron., which is not considered to be a valid name by many authorities; Still (1994) and Nui (1996) indicate that most cultivars are derived from various combinations of crosses among four taxa, Erigeron aurantiacus Regel (Orange Daisy, Orange Flea- bane), Erigeron glaucus J.B. Ker Gawler (Seaside Daisy, Seaside Fleabane), Erigeron speciosus (Lindl.) DC. (Aspen Fleabane, Garden Fleabane, Showy Fleabane), or Erigeron speciosus (Lindl.) DC. var. macranthus (Nutt.) Cronquist (Erigeron macranthus); Erigeron philadelphicus L. (Philadelphia Fleabane, Skevish) is a common perennial road- side weed or wildflower in North America with white to pink ray flowers and yellow to yellow-green disk flowers, while Erigeron annuus (L.) Pers. (Eastern Daisy Fleabane) is a widespread annual weedy species with small yellow button-like centers and white linear/filiform ray flowers; various regionally native species may hold potential for landscape use in various portions of the country and offer differing flowers, adaptation, and growth habits than the current commercially available cultivars. Erigeron procumbens (Houst. ex Mill.) G.L. Nesom Corpus Christi Fleabane (Aster procumbens, Erigeron myrionactis, Erigeron repens) • Also known as Beach Fleabane or Procumbent Fleabane, this Gulf Coast native lives up to its specific epithet which refers to its low growing growth habit; tight rosettes of suckering stems develop a dense slowly spread- ing canopy just a few inches tall; the semi-evergreen dark green obovate to spatulate leaves are 1O to 3O long ½O to 1O wide with cuneate bases and toothed or small lobed margins; these short stems root at the nodes where they contact soil creating a slow growing dense colony that works well as a small scale groundcover in the warmer portions of our region; in landscapes, avoid weed barriers which inhibit the rooting of these stems. • Numerous small ¾O to 1O diameter composite flowers open which display solid rings of ray flowers with fili- form petals surrounding compact tiny yellow disk flowers in the centers; petals of ray flowers may be blushed pink when opening; the frilly daisy-like composite flowers with button centers are held on slender erect pe- duncles 4O to 6O (8O) above the carpet-like foliage; the combination of successive flushes of white flowers on a dark green background makes a handsome effect; bloom will occur year-round where temperatures permit, but plants will die to the ground in regions with hard freezes and will tend to stall some in flowering in regions with very hot summers, where flowering will peak in spring and fall; while bluish flowers are sometimes re- ported in the literature, we have not observed such in this species. • Corpus Christi Fleabane is found in various environments in mostly sandy soils along the Western Gulf Coast, including within reach of lapping waves on coastal dunes and bay sides where its extreme salt tolerance is ex- hibited; it is also highly tolerant of heat and wind exposure, can survive moderately droughty conditions al- though it may wilt, and will grow in a wide range of soil pH conditions; plants can be propagated from seed or cuttings as they root easily; plants adapt well to container nursery / greenhouse production in a variety of sub- strates. • Potential uses for this species are many, coastal restoration, dune restoration and preservation, coastal and other saline landscape conditions, hanging baskets, small scale ground or bank covers, trailing over low wall or as a spiller in patio containers; bloom occurs over a very extended time and plants will bloom in full sun to light shade. • Mr. Sean Carver, a graduate student in our laboratory, has collected provenances from across the Texas range of this species as a part of his Masters work and has begun selecting for superior genotypes.