It’s a Pityopsis

Cover Story 

The first few “Goldenasters” that made it to Europe were not lumped into the genus Aster as were so many other small-flowered American Composites.  Rather, Linnaeus, Michaux, and Lamarck tucked the plants they encountered into the genus Inula, along with other yellow-flowered, chaff-less (epaleate) European composites.  By 1840, Nuttall had defined Pityopsis, but on and off since that time, the genus has been collateral damage in quiet skirmishes over the generic limits of their earlier-described, more noteworthy kin, Heterotheca and Chrysopsis (published between 1817 and 1823.)  

Today, these genera (which are three of the eight classified in the Chrysopsis Subtribe) have taken on a biogeographic dimension, with Pityopsis diversity centered in the Wiregrass and Florida Panhandle, Heterotheca mostly encompassing plants found in Western North America (with only the widespread Heterotheca subaxilllaris native to Florida), and Chrysopsis being essentially endemic to Florida.  

Florida Plant Atlas (ISB) documents 4 species of Pityopsis (Silkgrasses) present in the Apalachicola flora: Pityopsis aspera, P. flexuosa, P. graminifolia, and P. oligantha).  Only Pityopsis graminifolia is documented as present statewide, while P. aspera, P. flexuosa, and P. oligantha haven’t been reported outside the Panhandle.

The Main Story

Pityopsis have been commonly called “Silkgrasses” or  even “Goldenasters,” but recent usage seems to have granted Chrysopsis full title to the “Goldenaster” moniker, while our one Heterotheca is called “Camphorweed.”  That leaves Silkgrass cleanly applicable, which makes sense, since the terms “silky” and “grass” provide useful clues in field identification.  Basically, when in the Panhandle, if you find a small-headed daisy with both yellow ray and disk florets, open structure, capillary stems with few (or very reduced) leaves, and thin, flattened grassy basal leaves invested with lengthy schmears of silky hairs, you likely have a Pityopsis. To confirm that, you can check several characters.

Pityopsis produce heads of yellow ray and disk flowers with tight involucres of multi-seriate, narrow, green phyllaries. They lack pales (chaff) on the receptacle (basically bracts subtending florets), and produce pappi (papillary bristles) in two series, an inner, long capillary ring and an outer, very low (sometimes difficult to discern) crown of hyaline scales. Taxonomically, Pityopsis is circumscribed based on many characters, most obviously its grassy foliage bearing sericeous hairs and its spindle-shaped achenes (technically, its fusiform cypcelae.) 

The following field characters are good:

  • incredibly thin-textured and flat grassy foliage variously invested in sericeous hairs, 
  • open-branched structure of capillary stems, and 
  • clean yellow color to both ray and disc flowers. 

But identification requires two search images, one for Pityopsis oligantha and another that umbrellas the other three species. The larger-flowered P. oligantha stands out as having several long, somewhat equitant grassy leaves, stems typically ranging from 40 to 50 cm (1-1.5’) in height, with individual branches topped by medium-sized flowering heads, 3-4 cm across. It’s a  quintessential yellow “daisy,” bearing only one or two flowering heads at one time. In fact, the specific epithet “oligantha” implies “few flowered”.  There is little about the flower head that marks this plant as immediately distinctive,   The most useful clue comes with the foliage; you’ll find a few thin-textured basal leaves in a fan-shaped pattern, with 2-3 similar smaller leaves along the flowering stem.  The silky hairs are evident.

I seem to encounter Pityopsis oligantha in wet soils, where flowering specimens often stand out singly, from slender plants often matted in with grasses and other vegetation.  The plants are rhizomatous, but any colonial tendency can be masked in the density of surrounding vegetation, which also means you’re unlikely to spot plants when not in flower or fruit. However, we had an instructive encounter in early June, encountering plants flowering at a recent burned site. Timing must have been just right, such that the Pityopsis oligantha culms bolted immediately afterward. In the photo below, you see small colonies flowering absent the full complement of grasses and other vegetation.

Pityopsis oligantha is reported in the Panhandle, from Jefferson County westward, basically west of the Aucilla River. I find it in association with Rhexia alifanus, Calopogons, Eriocaulon, Aletris, Sarracenias, and Balduina, varying into slightly more ruderal associations, like Rhexia mariana and Polygala lutea.  Indeed, my first encounter with the plant was spotting non-descript clusters of yellow daisies springing up in verges along FSR 65, the “safety strip” that  gets mowed in early summer.  .   

The other three Pityopsis species have more of a candelabra look. They may branch basally, but the upper third of mature plants form open frameworks from 40-60 cm (1.5-2’) tall, with each branchlet terminated by a single head of yellow ray and disc flowers, many of which may be open at the same time, their rays spanning about 2 cm (an inch).  The breadth of their grassy leaves varies, but leaves of P. graminifolia are definitely broader and more evident.  Leaves bear long sericeous  hairs, and are prominent along the scapes. though greatly reduced in size (⅓ the size of basal leaves).

Most importantly, the flower heads (capitulae) of these three other Pityopsis species are much smaller than those of P. oligantha; similar, yes, but smaller. The photos below document flower size in a mixed population of Pityopsis graminifolia and P. aspera, in which only vestiture seems to differentiate the two types. Both show a flower head span of around 2 cm, as compared to the 3-4 cm spread in heads of P. oligantha.

I expect to encounter Pityopsis graminifolia in Pine Flatwoods as well as disturbed edges, though revisiting forested areas for this article I realized populations are not as ubiquitous as I might have imagined. 

Near Sumatra, in Apalachicola National Forest, I examined extended mixed populations of plants that key (based on the nature of trichomes) to Pityopsis graminifolia and Pityopsis aspera.  Photographs from that extended population (below) show the extremes in vestiture and leaf shape, along with a suite of aligned characters .  The “aspera” type (left image) has narrower leaves that arc away from the stem, more spherical immature heads, and of course their stems are sticky to the touch as they have stipulate glands rather than sericeous hairs.  The “graminifolia” type (right side image) produces broader leaves that, when still present, form more of a basal rosette (as compared to a somewhat more equitant arrangement), cauline leaves that nearly clasp the stem, and conical immature heads, and (of course) sericeous hairs on the stems as well as leaves.

I’m lacking good images of the fourth plant, Pityopsis flexuosa.  We were fortunate to see a population in flower last September, on a local FNPS tour with David Roddenberry and Loran Anderson.  It’s similar to Pityopsis aspera and P. graminifolia, but flowers in September and October. I revisited that population this May, and could easily pick out the foliage (and last year’s flowering stems), but aerial stems were not yet developing.

The Inside Story 

Flora of North America (FNA) treats 7 species in the genus.  Amusingly, the only taxon not recorded for Florida, Pityopsis pinifolia, is the type for the genus, and the plant from which Thomas Nuttall a prolific taxonomist, derived the generic name. Because that plant has long,  needle-like leaves (unlike Panhandle plants), his Pityopsis translates as “looking like Pine”, a reference repeated in the specific epithet pinifolia.  Nuttall published this combination in 1840 based on specimens from Georgia’s Sand Hills between the Flint and Chattahoochee Rivers (the sources for our Apalachicola River).  In the same paper, he pulled plants that were currently considered Chrysopsis graminifolia  (as well as the synonym Chrysopsis argentea) and Chrysopsis falcata into his new genus.  The group today remains reasonably aligned with Nuttall’s 1840 circumscription, the majority of species bearing biogeographic relationship to the Apalachicola flora, where plants are abundantly represented.

An excerpt from FNA explains current and historical botanical relationships of Pityopsis, Chrysopsis, and Heterotheca

Pityopsis has been treated historically as a distinct genus or as a section of Chrysopsis (A. Gray 1884) or Heterotheca (L. H. Shinners 1951e). J. C. Semple (1977) and Semple et al. (1980) presented cytologic, morphologic, and anatomic reasons for treating Pityopsis, Chrysopsis, and Heterotheca as separate genera. Semple and F. D. Bowers (1985) monographed the genus; their treatment is followed here. Semple and Bowers (1987) reported on the distribution of ploidy levels within the genus. In a preliminary cladistic study of the Chrysopsidinae, Pityopsis was consistently separate from Chrysopsis and Heterotheca (Semple and L. Tebby 1999). L. Brouillet (pers. comm.) noted that DNA sequence data also indicate that Pityopsis is separate from Chrysopsis and Heterotheca. Semple and J. L. A. Hood (2005) described additional differences among the pappi of Chrysopsis, Heterotheca, and Pityopsis.

The Flora of North America treatment for Heterotheca explains the nature of floral limits with in this group (Subtribe Chrysopsidinae), based on work of John Semple and associates:

The generic limits of Heterotheca used here are those of J. C. Semple et al. (1980), who included all goldenasters with stiff, gradually tapering, multicellular hairs with bone-shaped cells with knobby faces, regardless of whether or not they had dimorphic cypselae. Traditionally, only dimorphic species had been included. L. H. Shinners (1951e) found that some individuals of the H. subaxillaris complex sensu G. L. Nesom (1990e) are not consistently dimorphic. He thus proposed merging the genus Chrysopsis, including Pityopsis, into Heterotheca. V. L. Harms (1965) reported cytologic evidence supporting this merger and followed Shinners in subsequent papers (e.g., Harms 1970). Semple (1977) and Semple et al. (1980) presented evidence that Chrysopsis and Pityopsis differ sufficiently to be treated as separate genera based on habit, hair, leaf, cypsela, and cytologic traits. Nesom (2000) recognized Heterotheca as delimited here, following Semple et al. (1980) and Semple (1996)…. The common name “false goldenaster” appears to have been arbitrarily coined recently and subsequently used on the web site, as are many of the common names listed for species. Historically, the common names “camphorweed” or “telegraph weed” were applied to the taxa with dimorphic cypselae, while “goldenaster” or “golden aster” was applied to the taxa with monomorphic cypselae (i.e., those that had been included in Chrysopsis in the broad sense). The common name “goldenaster” is preferred and was used in Semple (1996).

The Side Story

It’s worth mentioning that Pityopsis are not the only plants with creamy-white sericeous hairs.  Leaves of one of the better-known Golden Asters, Chrysopsis mariana (described as Inula mariana by Linnaeus), are quite endowed with these kinds of trichomes. See the images below:

Flora – Main Index Page

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