Prairie Flora in North Carolina: The Partheniums

Dense Quinine patch in Durham County;
plants in the foreground are P. auriculatum, taller
stems in background are P. integrifolium

Wild Quinine (Parthenium integrifolium) and Glade Wild Quinine (Parthenium auriculatum) are frequent and sometimes common members of North Carolina Piedmont diabase woodlands. For unknown reasons, they may co-occur (as in the image to the left) or be found singly at a given site.

Both flower profusely in open, prairie-like sites, especially after burning although individuals may persist vegetatively for long periods under somewhat shaded conditions.

Wild Quinine is the wider ranging of the two, being found nearly throughout the eastern US (where often associated with high quality, prairie or savanna-like habitats). Glade Wild Quinine is the southern cousin ranging roughly from West Virginia to Alabama. The former may be found nearly across NC, while the latter is restricted to a handful of Piedmont counties.


     

Typical P. auriculatum
basal leaf

Typical P. integrifolium
basal leaf

              

                 

Both species have similar appearance with large, coarse, basal leaves.












P. integrifolium is much less hairy, often has a dark reddish mid-vein apparent on the larger, mostly basal leaves. It also tends to be a taller and larger plant when flowering (up to 3' or so).  P. auriculatum has a more petite, compact form, and longer blooming period. The toothier leaf margins help distinguish Glade Wild Quinine, and many plants show a sheen of white pubescence even from a distance while the hairs on Wild Quinine are much less developed and obvious.



The upper image (right) is Parthenum auriculatum, the lower is P. integrifolium; both in full flower (an insect has chewed into one on the lower plant.





           

Wild Quinine patch flowering after late spring
prescribed fire in Durham County
on exposed diabase outcrop

Large expanse of Parthenium integrifolium on a clayey, upland flat with deeper soils derived from diabase.
Site burned early Spring

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Ascending the Slippery Slope of Restoration

For several years now, I and the NC Plant Conservation Program have been working with the Eno River Association to restore their oldest Nature Preserve, the Blue Indigo Slopes.  The site is important, in part, due to the rare plants present as well as frontage on the Eno River . In addition, we view it as an important stepping stone in a landscape-level pollinator pathway in northern Durham (perhaps I will explain what that is in a future post).

During a routine visit this year, late in June, I noted general ecological conditions of the site and recorded mental notes on additional ecological restoration needs. A few observations follow:

Flowering Spurge (Euphorbia corollata)
widespread in eastern U.S.
often found in open sites or prairies
a few stems flowering here and there on the Slopes in esp. open areas

Piedmont Barbara's Buttons (Marshallia obovata)
locally abundant in some of our open, burned sites; this specimen
was flowering much later than typical for the species in our area
a small colony is present on the site

Post Oak (Quercus stellata) and Blackjack Oak (Quercus marilandica) sprouts and seedlings were apparent around the open edges of the site (see below). I think of these two oaks as likely historically important in many Piedmont open woodlands and savannas; both tolerate fire well. However, Blackjack is especially intolerant of shade and may be easily overwhelmed by faster growing, shade tolerant species - a major reason it is rarely seen today in the region.

Top: Blackjack Oak (Quercus marilandica) sapling amidst prairie flora
Bottom: Post Oak (Quercus stellata) sapling near clumps of Eastern Gamma Grass

Like many other rare plant sites in the Piedmont, this site was historically more open & prairie-like. A common attribute of these sites is the tendency to become heavily overgrown by dense trees and shrubs, presumably due to the absence of fire or grazing. One result of this change is the decline of  many understory species that are now of conservation concern and require special efforts to restore their populations.

We have begun an ecological restoration program supported by the Eno River Association Board, staff, and volunteers. Part of the restoration has involved slowly removing trees (mostly Loblolly Pine) and other invading brush from the site. As part of the broader effort we also conducted two consecutive spring-time prescribed burns on the Preserve. 

Results are becoming apparent!

The images above show a portion of the site before and after preliminary ecological restoration 

(November 2007 & February 2013); 

Note the large, limby eastern red cedar on the right side of both images

The green "clump" in the middle of the 2013 image is a shortleaf pine sprouting after fire

images complements of Kurt Schlimme of the Eno River Association.

The site's namesake, Wild Blue Indigo (Baptisia australis var. aberrans), suffered for years under the growing canopy. A decent number of individuals are still present but most are relatively small and still show diminished flowering. Consequently, very few of the individuals actually produce fruit. The individual shown below has only a single pod this season and appears to be affected by powdery mildew or some other pathogen. Although I don't know the identity of the white substance illustrated below we did document powdery mildew on these plants several years and a pathologist suggested heavy shade and associated moist conditions were contributing factors. We have purposely "gone slow" on the canopy re-opening, but the continued relatively poor vigor and possible mildew problems on the Wild Blue Indigo suggest we need to renew and expand our efforts. 

Newly developing Prairie Wild Blue Indigo Pod (Baptisia australis var. aberrans)
Typical "healthy" plants produce numerous pods, this is the lone pod on this individual

The site supports a scattered population of Starry Rosinweed (Silphium astericus) (left below) just coming into flower, as well as numerous Glade Wild Quinine (Parthenium auriculatum) (right below). As with the Blue Indigo, relatively few of the Glade Wild Quinine appear likely to flower this year.

An open prairie-like portion of the Eno River Association's Indigo Slopes Preserve (above). A Post Oak sapling can be seen near the back of the opening near the large pines, a Prairie Wild Blue Indigo individual occurs on the right, and scattered rosettes of Glade Wild Quinine (Parthenium auriculatum) can be seen throughout. The extent of the opening is less than 1/4 acre and surrounded by dense woods on at least 3 sides. We hope to significantly expand this opening, both up and downslope, in the near future.

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