Cabbage Time in Carolina!

Skunk Cabbage (Symplocarpus foetidus) is one of our earliest, native bloomers. In mid-February, I observed dozens, possibly hundreds, of individuals pushing up through leaf litter, muck, and shallow water at a site near Warrenton, NC.

The stout emerging stalks are amazingly thick and leathery to the touch. They unfurl at various rates to form leafy "spathes".  I observed incredible variation in the appearance and coloration of these, ranging from light green to heavily striped, to mottled, to almost solid dark red.




Skunk Cabbage is a member of the Araceae family, which includes mostly tropical species. In our area its closest relatives include Golden Club & Jack-in-the-Pulpit.  Symplocarpus foetidus is the only species of the genus in North America; Western Skunk Cabbage belongs to a different genus. Symplocarpus also includes some disjunct members in eastern Asia. It has been suggested the Asian and North American species of Symplocarpus have been isolated from one another for over 6,000,000 years (1).

Symplocarpus foetidus spathe; few plants observed had
developed this perfect oval shape
Warren County, NC (Feb 2015)

Skunk Cabbage open spathe revealing enclosed spadix,
Note the amount of water inside the spathe

Skunk Cabbage is famous for the ability to produce heat during early season flowering, a process sometimes called "thermogenesis". Indeed, S. foetidus is one of the most precise thermoregulators known, and is apparently able to maintain temperatures within ~ 3.5 ° C range, while ambient temperatures range over 37.5 ° C (2). Exactly what value thermogenesis conveys to the plant, if any, is unclear. Some believe it is an evolutionary hold-over present in a few primitive plant families.

According to Seymour & Blaylock (3), "there is no doubt that warming advances development and permits early flowering, but the adaptive value of this is obscure".

I observed several plants with groups of what appeared to be fruit flies buzzing around. Some authors have suggested the plant's thermogenic qualities provide a more attractive site for early season insects like these. Grimaldi & Jaenike (4) found that Skunk Cabbage is "a major breeding site" for one species of fly that "looks enough like Drosophila so that the casual observer might be confused" (5); I certainly wouldn't have known the difference! Whether these insects pollinate the flowers on the spadix is unclear.

Symplocarpus foetidus "ripe" & flowering spadix

The condition and maturity of the spadix and presence or absence of flowers was quite variable during my visit.  The following series of images shows a bit of this, as does the image above (with the dark brown spadix). However, very few spathes were open enough to easily reveal the contents. Even fewer were flowering, like the examples shown to the left. Several appeared to be just past and others much more so, while at least one spadix (below) seemed to still bedeveloping.

S. foetidus immature spadix

This ripening spadix was
lying in an open spathe,
like an Easter Egg waiting to be gathered

Bright yellow stamens exposed, zooming into these seems to show pollen that has
fallen onto the spadix surface 

North Carolina has the southernmost ranging populations of Skunk Cabbage is eastern North America. The species creeps into a few northern mountain counties in eastern Tennessee and western NC. Further east, there are 3 or 4 reported counties in the NC piedmont.  The site for these images is in Warren County, close to the Fall Line.  Although often considered a piedmont county, it sure felt like I was in the coastal plain.  The habitat was a non-alluvial wetland ranging from moist to mucky soils. Tulip Poplar & Red Maple were probably the dominant trees, but Black Gum and an occasional Pond Pine were present, Cane & White Bay Magnolia were common as well. Most of the plants were found in and around the muckiest and wettest area near the streamhead.

Skunk Cabbage habitat (Warren County); Feb 2015
most plants occurred above the standing water where a faintly developed "Y"
can be seen, just downstream a dense understory of cane develops

Skunk Cabbage habitat, same site as previous (April 2014)

References:
(1) Jun Wen, R.K. Jansen, and K. Kilgore. 1996. Evolution of the Eastern Asian and Eastern North American disjunct genus Symplocarpus (Araceae): Insights from chloroplast DNA restriction site data. Biochemical Systematics & Ecology 24: 735-747.
(2) Seymour, R. S. 2004.  Dynamics and precision of thermoregulatory responses of eastern Skunk Cabbage. Plant, Cell,& Environment. 27: 1014-1022.
(3) R. S. Seymour & A.J. Blaylock. 1999. Switching off the heater: influence of ambient temperature on thermoregulation by eastern skunk cabbage (Symplocarpus foetidus). Journal of Experimental Botany 50: 1525-1532.
(4) D. Grimaldi & J. Jaenike. 1983. The Diptera Breeding on Skunk Cabbage, Symplocarpus foetidus (Araceae). Journal of the New York Entomological Society 91: 83-89.
(5) H. D. Stalker, 1945; On the Biology and Genetics of Scaptomyza graminum Fallen (Diptera: Drosophilidae).

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Purple Mountain Pitcher Plants - New & Improved!

Purple Mountain Pitchers grow well in naturally occurring beds of Sphagnum moss
like these growing wild in Transylvania County, NC

Ron Deterrmann, has been tireless in his efforts
to secure conservation for Purple Mountain Pitchers  

                                                               Purple Mountain Pitcher Plants occur naturally only in a small region of the southern Appalachians (western NC, adjacent SC and GA).  There has been relatively little conservation attention focused on this narrow endemic, in part due to the relatively recent recognition of its distinctiveness. Schnell & Determann (Castanea 1997) published the new varietal status, thereby bringing needed attention to these unique plants.  


The NC Plant Conservation Program "protects" portions of two of the 8 known populations in the state (although perhaps more populations will become known as the NC Natural Heritage Program is just beginning to keep documentation on this plant for the first time (2014).

One of two protected populations mentioned above has approximately 150 clumps of pitchers and comprises what is thought to be the largest known population in the state. It is unclear why this population is so large compared to others in the region.  We do know that Sarracenia purpurea spreads slowly; Ellison & Parker (American Journal of Botany 2002) documented only a 5 cm median dispersal distance for pitchers in the northeastern US.  Further, Gotelli and Ellison (Ecology 2002) found that Purple Pitchers don't reproduce until individual rosettes reach 10 cm in diameter.  Our Southern Apps variety grows vigorously and flowers profusely in sunny & open habitats, as shown in the following image. In contrast, pitchers subjected to heavy

Mass flowering in an open, sunny, yet constantly moist habitat

shade lose vigor, diminish in size, and cease flowering.  The example shown below displays etiolated leaves typical of shading. This clump is actually smaller than the surrounding Galax foliage and has little chance of flowering or trapping insects. The site where it occurs has been heavily shaded for 20 + years.  It is unclear how long an individual pitcher clump or rosette can survive in dense shade.  Gotelli & Ellison (Ecology 2002) suggest rosettes may persist for 30-50 years, but this longevity is likely to be strongly affected by shading.  In any case, the diminished vigor translates to loss of reproduction, perhaps a significant reason other known populations are much smaller.  

Our large population was almost certainly larger at one time. We have documentation that the pitchers were "once so plentiful they sold for 50 cents a piece".  Even today, pitchers continue to be taken or poached hindering population expansion.  The first image below shows where an entire rosette was taken (depressed area directly in front of the remaining clump). The second image shows a clump partially removed (note the bud forming).  I guess in both cases the losses could have been far worse, eco-conscious poachers?

In spite of the poachers, we have extensively re-opened the site by removing dense shrubs.  Precise demographic data are lacking but we counted 32 flowers in 2012, 94 flowers in 2013, and 114 flowers in 2014. The majority of these flowers seem to be producing seed heads. It has been estimated that Northern Pitchers produce approximately 1000 seeds per head (Gotelli and Ellison, Ecology 2002). Although germination rates may be low, if seed production continues the population could begin to rebound. In fact, on a recent visit Ron Determann pointed out a few true seedlings..... with luck, continued management, patience, and support of our local poaching community the population may continue to rebound!

Purple Mountain Pitcher seed capsule 

Seedling Purple Pitchers

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Prairie Flora in North Carolina - All Hands on Dock (Silphium terebinthinaceum)

Prairie Dock (Silphium terebinthinaceum), a.k.a Prairie Rosinweed, is among the most conspicuous herbaceous perennials of tallgrass prairies of the midwestern United States (1).  The same is true for certain remnant, prairie-like habitats in parts of the NC Piedmont as well. Part of its conspicuousness, no doubt, comes from the distinctive & large basal leaves that may reach 12" in length (see image below).

Flowering stalks bolt upwards in late July & early August, topped by ball-like buds. Stalks may reach 6-10 feet in height before opening into bright yellow flowers around mid-August.

Silphium terebinthinaceum basal leaves in Durham Co, NC

The epithet, "terebinthinaceum" translates to "with turpentine" a reference to the presence of rosins which give many species in the genus their common name. I assume the rosin content would be toxic or inhibitory to grazing animals, but rumor has it that the "rosin" was once chewed by pioneers and that the plant is actually favored by some grazing animals. Curtis (2) apparently observed a "virgin prairie" when it was first put to use as a livestock pasture. He indicated that the horses and cattle sought out prairie docks and compass plants "like hidden candy at a child's birthday party."  There are suggestions that bison also feed upon Prairie Dock, but I have found no definitive references to this, possibly because their ranges no longer overlap.

Prairie dock develops a significant taproot (see image at Reference # 3), unlike Silphium astericus with which it commonly co-occurs on many Piedmont, North Carolina sites. Dhillion & Friese (4) found that Silphium terebinthinaceum had high levels of mychorrhizal activity (a symbiotic association between the roots and specialized fungi that often confer advantages to the plant in the form of drought resistance, nutrient uptake, etc.).

Very little seems to be known about seed dispersal or pollination, but there are strong suggestions that both are extremely distance limited. Coupled with habitat fragmentation, the result is extreme isolation between remaining populations.

A review of the S. terebinthinaceum range map (see also #5) indicates that North Carolina populations are the easternmost in the nation, significantly disjunct from the heart of the main population centers in Illinois and Missouri (2). What is it doing here in the Piedmont of North Carolina?
 
                         

The NC Natural Heritage Program records Prairie Dock occurrences in Cabarrus, Davie, Durham, Granville, Mecklenburg, Stanly, Union, & Wake counties. Populations in Durham & Granville occur on rich clayey soils apparently weathered from diabase rocks, often with other species with prairie affinities. Until such sites are managed to maintain, or recreate, open conditions Prairie Dock appears to decline and persist only on road edges and powerlines.

Prairie Dock rosettes persisting along roadway in Durham (2006);
lack of mowing allowed dense saplings to encroach & suppress
 most individuals present

Same site as previous; mowed during growing season (May 2007)

Same site as previous; note numerous Prairie Dock rosettes (Sept 2007)

For long-term habitat improvement & maintenance prescribed fire is the most desirable technique and we have applied it with spectacular results at several Piedmont sites.  In most cases, our spring fires move relatively rapidly, exposing individual plants to direct heating for a short amount of time.  Hahn & Orock (6) found that Prairie Dock seeds are able to maintain viability even after 15 minutes of exposure to 150 degree C!

I concur with Schramm (6) "one would think that by now, fire would be universally accepted and vigorously applied in all restoration and management efforts, but fire is being used to conservatively." In addition, he says, "most remnants ... currently need regular burning to regain their original quality", a statement I also agree with in the Piedmont where prairie associated flora remains.

A grove of Prairie Dock flowering (Aug 2014) at site in Durham Co, NC
(same site as shown in preceding sequence)

REFERENCES:
(1) Gleason H.A. and Cronquist A. 1991. Manual of Vascular Plants of Northeastern United States and
Adjacent Canada. 2nd ed. The New York Botanical Garden, The Bronx, New York.
(2) Curtis, J.T. 1959. The Vegetation of Wisconsin. UW Press.
(3) Robertson, K. R. 2007 image.  see - http://www.inhs.uiuc.edu/~kenr/prairiephotos/silptere.root1.jpg
(4) Dhillion & Friese; http://images.library.wisc.edu/EcoNatRes/EFacs/NAPC/NAPC13/reference/econatres.napc13.sdhillion.pdf)
(5) http://plants.usda.gov/core/profile?symbol=SITE
(6) Hahn P.G. & Orock, J.L. 2014. Effects of Temperature on Seed Viabaility of Six Ozark Glade Herb Species and Eastern Red Cedar (Juniperus virginiana). American MIdland Naturalist 171: 147-152
(7) Schramm, no date; http://images.library.wisc.edu/EcoNatRes/EFacs/NAPC/NAPC12/reference/econatres.napc12.pschramm2.pdf

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Two Rare Botanists on a Witch (grass) Hunt

  

Dichanthelium is "perhaps the most complex and confusing genus in our region" (1). 

Sometimes a mere one tenth of a millimeter difference in a critical measurement can separate two taxa!
For obvious reasons, most folks avoid these smallish and difficult to identify grasses (do you have a micrometer handy?).

But Johnny Townsend of VA Natural Heritage Program (below right) and Richard LeBlond  (right) (formerly of NC Natural Heritage Program) are hardcore enough not to be afraid of the Witchgrasses!

I had the unexpected pleasure to show them around to a few sites in Durham County recently. 

Johnny rarely travels to NC; the Commonwealth keeps him quite busy. 

Richard told me he had never really botanized in the Piedmont before.  

But they came & hopefully will both return!

On this day it was a quest for rarities; mostly taxa that Richard had either named or is working on, and that had been showing up in VA recently. We all hoped they would turn up on one or more sites nearby as well!

After a brief orientation, including review of some pressed specimens Johnny had brought along, Herb & Pat Amyx, Thomas Blaine, and the rest of us headed off in search of live material.  I found it difficult to train my eye to seperate the Dichantheliums from the other vegetation. More difficult was rapidly distinguishing the common species at a mere glance, like Richard and Johnny were able to do.

After traipsing by 7 or 8 other taxa in the genus, innumerable other native species, and just as the sun and humidity seemed to be peaking, Johnny dropped to one knee in front of Ringed Witchgrass (D. annulum). One of our targets was found! Was it the humidity or the excitement that made my legs buckle slightly?

Dichanthelium annulum displaying "autumnal" growth

Ringed Witchgrass was given its currently accepted name in a publication by Richard LeBlond in 2001 (2), elevating it from its former genus Panicum (along with a host of others).


Dichanthelium annulum is considered "significantly rare" in NC. Records have been documented from 15 locations around the state, but only 2 are considered extant in the Natural Heritage Program database (the other locations are historic, meaning they have not been observed for decades).




The bulk of the historic reports are from Piedmont counties including Person, Orange, Wake, and Durham (no apparent coastal plain records but Richard has just informed me of a collection from Roanoke Island!). The habitat has been listed in Weakley's flora as "dry sandy or rocky soil of open woods, dry grasslands, and barrens and glades..." Our site was in a frequently burned, open oak-hickory woodland, on rich clayey soils, with a diverse native ground cover.

Several stems of D. annulum rising above
Partridge Pea (Chamaecrista fasciculata), Earle's Blazing Star (Liatris squarrulosa),
Maryland Senna (Senna marilandica), and others

Most stems of Ringed Witchgrass were relatively tall (over 12") and showed the remains of spring culms and panicles. Roughly 1/3 of the way up the stem were tufts of new leaves slightly hiding newly developing branches or panicles. We found plants in several locations in the first site visited, usually in places where taller plants seemed to be less frequent. With this find, we can once again consider D. annulum "extant" in Durham County. 

After continued traipsing and hunting we visited another site. It wasn't long before Johnny made the second significant find of the day.....in a relatively bare patch of rich soil, exposed by recent spring prescribed fire.

Given the local conditions, this taxon was easier to see but harder to explain taxonomically. Currently treated as Northern Witchgrass (Dichanthelium boreale), but also indicated as Panicum bicknelli (1) Richard is working toward a nomenclature change that will treat this as Dichanthelium bicknelli. Regardless of the taxonomy, the plants found are also considered "significantly rare" in North Carolina.  If all the existing records are assigned to the same taxon, this will constitute the 13th or so record in the state, most of which seem to be considerably west of Durham, mostly in the mountains.

Very similar habitat (although not co-occurring) to Ringed Witchgrass, but overall, a much different appearance. These plants were much more clumpy than D. annulum with abundant, sturdier, basally disposed leaves.  An obvious rosette was present (below, left): perhaps these will be the overwintering leaves present in many species? Numerous flowering culms were present (below, right).

References:

(1) Weakley, A. S. 2012. Flora of the Southern and Mid-Atlantic States
(2) LeBlond, R.J. 2001. Sida 19: Taxonomy of the Dichotoma Group of Dichanthelium (Poaceae)


PARTING SHOT:

Richard LeBlond (right), "bowing down" before a rare specimen of (soon to be) Dichanthelium bicknelli. 

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Prairie Flora in North Carolina: Eastern Gamagrass

Tall culms of Eastern Gamagrass in a "Piedmont Prairie" in central NC
with Daniel Overcash & Louis Suther

Eastern Gamagrass (Tripsacum dactyloides) is one of North Carolina's tallest and most robust native grasses.  A clump forming, warm season, perennial, with flowering culms that can reach 7-8' in height, the species responds well to fire and thrives in open sunny, yet somewhat moist sites.

Flowering Tripsacum dactyloides with pistillate (below)
and staminate flowers (above)

Tripsacum is monoceious, producing both male (staminate) and female (pistillate) flowers on an individual inflorescence.

Tripsacum is perhaps one of the most ecologically and agriculturally important native genera from North America. Widespread throughout the eastern US, Mexico, & parts of S. America, Tripsacum was a key ancestor of modern day corn (1) and could eventually contribute to agricultural sustainability efforts focused on perennial rather than annual crops.  At least one cultivar has been developed between Gamagrass and Zea mays that may be a step in that direction (2)

Tripsacum patch expanding in old field at Manassas Battlefield, VA

It produces significant live, leafy biomass with high live - dead ratio and is highly palatable for many grazers. Because of this excellent forage quality, Gamagrass is a classic "decreaser" in range management terminology; when present, grazers actively and preferentially seek it out and cause it to decline under sustained pressure.

Tripsacum dactyloides cupule with persistent pistillate flowers

In mid-summer, large seeds develop and ripen progressively from the top, eventually disarticulating when ripe (see image, right). Due to their size, they have little chance of dispersing far from the mother plant. Under intense grazing pressure or declines due to other factors, it is easy to understand why Gamagrass would be slow to recolonize. Heavy seed predation by rodents may also be a limiting factor in spread (3).

Individual seeds are enclosed in a hardened case sometimes called a "cupule". When intact, this structure can inhibit germination of the enclosed seeds (3)

Tripsacum dactyloides cupules on mineral soil 

Large clumps of Gama tend to develop a characteristic "hollow" in the middle of an almost circular ring of leaves.  As the clump develops upright stems, a tent of sorts forms over the nearly bare middle, providing nesting habitat for a number of ground nesting birds associated with prairies (4). Many such birds are among the most declining in the Piedmont region.

Tripsacum clump developing concentric ring,
 beneficial to some ground nesting wildlife

Herb Amyx, Joan Schnier, John Thomas, Jon Stucky
observing a riverside patch of Tripsacum

As suggested by its relatively wide natural range, Gamagrass is adaptable to a host of conditions. In part, this is due to extensive aerenchyma  root tissue (essentially air passages) that allow it to thrive in wet or even infrequently flooded situations (see image, left).

In addition, the roots are able to penetrate restrictive soils (including claypans) and survive droughts and other limitations that other species can not (5).






Consequently, Eastern Gamagrass can be an important member of a number of natural community types. These include certain blackland prairies in Texas (5), and coastal prairies in Louisiana and Texas (6). I have also observed Gama as locally abundant or dominant in longleaf pine woodlands in eastern Texas and other remnant, prairie-like communities in southeast Texas. In North Carolina, Tripsacum is an important member of what may be North Carolina's only remaining prairie, and is becoming locally abundant in several frequently burned areas elsewhere in the Piedmont providing clues to other habitats it may have occurred in.

Gamagrass clumps in an open woodland in which prescribed fire has been used twice
Durham Co, NC

Although Tripsacum dactyloides appears to be indicative of prairie-like habitats across North Carolina, and perhaps through its natural range, I hesitate to suggest "introducing" it to natural areas without first applying regular prescribed fire (and having the means to continue to do so), obtaining open habitat structure, removing invasive plants, and having a pretty good indication it may have been present historically.  Having said that, not every "restoration" of such habitats needs Gamagrass or likely ever had it. I prefer allowing even like sites to have their own unique floristic assemblages.

References:
(1) Eubanks, M. 2001.  The origin of maize: evidence of Tripsacum ancestory. Plant Breeders Reviews
(2) http://www.google.com/patents/US20140123357
(3) Anderson, R.C.  1985. Aspects of the germination ecology and biomass production of Eastern Gamagrass (Tripsacum dactyloides). Botanical Gazette 146.
(4) http://www.houstonaudubon.org/default.aspx?act=newsletter.aspx&category=Natives &newsletterid=1730)
(5) see http://link.springer.com/article/10.1023/A:1004256100631#page-1
(6) http://images.library.wisc.edu/EcoNatRes/EFacs/NAPC/NAPC04/reference/econatres.napc04.ocollins
(7) Diamond, D. D. & F. E. Smeins. 1984. Remnant Grassland Vegetation and Ecological Affinities of the Upper Coastal Prairie of Texas. Southwestern Naturalist 29.

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Another Unexpected Discovery - Out of the Ashes

Michaux's Sumac (Rhus michauxii); Durham County (2014)

A series of unexpected and seemingly unrelated events (including encouragement from great volunteers, a last minute field trip venue change, perfect burn weather one fine spring day, a drenching downpour & flooded creek one late spring day, a new fire management partnership, etc...) conspired to produce spectacular results. 

In mid-May we held a field trip for members of the Friends of Plant Conservation (http://www.ncplantfriends.org). Guests and leaders alike were impressed with the results of a spring-time prescribed burn. Photo opportunities abounded (see image, left). There is nothing like seeing freshly sprouting plants invigorated after a burn!

While most people were snapping photos, some on their hands & knees, Lesley Starke called me over. She pointed to the small, hairy shrub (pictured above) and said, "is that what I think it is?"  But she already knew; we both instantly knew!  It's not every day one finds a new population of an endangered species, especially one of the rarest shrubs around.

Lesley Starke admiring her unexpected find

MICHAUX'S SUMAC IN DURHAM!!

What made this such an unexpected surprise? No previous survey work had associated Michaux's Sumac with these particular soils, and we did not believe the species native to the county.  Sure, there was a planted population elsewhere in the county but what did that mean? We had been frankly fixated on the other rare species present, namely Smooth Coneflower (Echinacea laevigata). Finally, the area had been literally "out of site and out of mind". Other than a single prescribed fire we conducted years ago, this area had received no management attention. The last time we burned nearby,  the area was avoided and had been languishing ever since. Fortuitously, early in the year I made a brief visit to the area with Herb & Pat Amyx.  We observed excellent restoration potential evidenced by numerous rosettes of Parthenium, and Helianthus atrorubens; we speculated on what might appear with appropriate restoration. Game on......and the hard work began.

We got an answer to our earlier speculation this May when over 40 stems of Michaux's Sumac were found!

Sumac Site shortly after prescribed fire & clearing

An abandoned railroad track runs through the middle of the site. In preparation for a controlled burn woody vegetation was cleared around the RR line (which also served as the fire line). The dense, dark woods toward the back right remained uncleared but were included in the initial fire; this tree density was typical across the entire length of the tract. 

Same view as above (approx.) several weeks later;
note flowering Sumac in foreground

Fire scars are evident on boles of shortleaf pines from the prescribed burn & orange-brown vegetation (back left) was top-killed by a more recent prescribed burn. The brush pile is one of many created from hand clearing.

During the prescribed fire, dense piles of pine needles and other leaves burned deeply exposing the RR ties underneath (we had stationed a pump unit there to wet the ties before they could ignite). All we really hoped for was flowering of the common species to benefit pollinators.

Michaux's Sumac (Rhus michauxii) flowering stem (foreground) with fire (background)

Michaux's Sumac (Rhus michauxii) was listed as federally endangered in 1989.  Although also endangered in North Carolina, the species is doing reasonably well in the sandhills region, where protected land and prescribed burning are relatively common. Populations in North Carolina's Piedmont have been all but wiped out. Loss of habitat to development and fire suppression are among the main culprits.

NOTE: Herb Amyx produced an excellent article on the Sumac which can be viewed here: (http://bwwellsassociation.wordpress.com/)

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