Sunday, November 30, 2014

New(ish) to Carolina & Not Wanted: Spurred Anoda

Spurred Anoda in Catawba County, NC
Image Date: 9/12//2013
Spurred Anoda (Anoda cristata) is poorly documented in the Carolinas and was listed as "rare" and known only from Mecklenburg Co, NC in the Manual of the Vascular Flora of the Carolinas (Radford, Ahles, Bell, 1964).

The native range of Spurred Anoda is unclear but likely includes the southwestern US, and South America (where it is also considered an agricultural pest). In Mexico, there are numerous references documenting the uses of this species for food and medicine; the plant apparently contains significant amounts of ascorbic acid, retinol, iron, proteins and carbohydrates (see Bautista-Cruz et al., 2011; Journal of Medicinal Plants Research).

In Virginia, the species has been documented relatively widely in the coastal plain but only rarely in the Piedmont ( An online search of the South Carolina atlas turned up only a single collection. In NC, the second documented report of the species comes from the northern Mountains,  "one of the three adventive species derived from bird seed waste" found growing under a bird feeder near Boone (see Poindexter et al., 2011; Phytoneuron).  I located what appears to be the 3rd known station for the species in NC in the Piedmont region (Catawba County) growing at the margin of a corn field along with a number of other agricultural weeds such as Cocklebur (Xanthium strumarium), Johnson grass (Sorghum halepense), Red Morning Glory (Ipomoea coccinea), and Pigweed (Amaranthus sp.).
Habitat location for Spurred Anoda in Catawba County along Carolina Thread Trail;
plants were growing at the very edge of the corn crop

Surprisingly, given the botanical status mentioned above, Spurred Anoda was listed as one of "Ten Most Troublesome Weeds In Cotton" in both NC and SC (see 2005 Proceedings, Southern Weed Science Society, 58).  In the Carolinas, it is unclear if the species is simply overlooked and under-collected by botanists or remains truly rare in NC & SC. The fact that Spurred Anoda appears to spread from commercial seed mixes is troubling and perhaps doesn't bode well for its future status in the state.

In the field, plants have light bluish/lavendar, 5 petaled flowers with radial symmetry, forming in the axils of leaves. Leaves are widest at the base, sometimes developing three lobes. Fruits, sometimes referred to as hemispheric schizocarps, are flattened, circular, segmented structures. Dense hairs are found on the stems, fruits, and less so on the leaves.  This is an annual which apparently spreads well from seed.

Sunday, November 16, 2014

Large-flowered Milkweed (Asclepias connivens)

Large-flowered Milkweed is one of the more distinctive milkweeds of the southeastern states, due to the unusually large, deeply cupped, individual flowers, that may reach nearly an inch across.

Individual flower (corona) of Asclepias connivens, displaying the "connivent" hood
Phylogentically, A. connivens is intermixed with African Milkweed species in clades developed by Fishbein (1996), providing some suggestion that our North American species may be derived from Africa; perhaps this implies this is also one of our more ancient species?

Large-flowered milkweed is a relatively narrow southeastern coastal plain endemic, ranging from extreme southeastern SC through coastal GA, into extreme southern AL, and across most of Florida, In the northern Florida panhandle, Asclepias connivens can be found in poorly drained, silty soil habitats that have been called wet flatwoods or prairies (Carr 2007); these sites have sparse tree canopies and well developed herbaceous layers.  The images included here are from two regularly burned sites taken on the same date. Plants at the most recently burned site were somewhat delayed in flowering compared to the site burned earlier in the season.

A. connivens coming into bloom in
standing water, recently burned savanna
(July 04, 2014)
A. connivens flowering in dense sward of grasses and herbs
under sparse canopy of longleaf pine
(July 04, 2014)

One of the sites could also be called a "wet savanna".  It had a sparse tree canopy of longleaf pine and a few Pond Cypress (Taxodium ascendans), including the two tallest stems shown in the midground below.  Some naturally occurring slash pine (Pinus elliotii) were present (seeding in from the adjacent forested wetland), but most of the smaller stems were killed by the last prescribed fire. In addition to numerous stems of Large-flowered Milkweed other notable species included Toothache Grass (Ctenium aromaticum), Parrot Pitcher Plant (Sarracenia psittacina), Pale Grass Pink (Calopogon pallidus), and Tracy's Sundew (Drosera tracyi)
Awesome wet savanna on St. Marks National Wildlife Refuge
Thanks to Jeff Glitzenstein for getting me there!


Carr, S.C. 2007. Floristic and Environmental Variation of Pyrogenic Pinelands in the Southeastern Coastal Plain: Description, Classification, and Restoration. PhD Dissertation.

Fishbein, M.  1996. Phylogenetic Relationships of North American Asclepias and the Role of Pollinators in the Evolution of the Milkweed Inflorescence.  PhD Dissertation.

Saturday, November 15, 2014

A few Southeastern Coastal Plain endemics

Shiny Woodoats (Chasmanthium nitidum)
Wet hardwood hammock,
limestone close to surface
St. Marks NWR, July 2014 

Probably the rarest Woodoats grass or Chasmanthium species in North America, the natural range of Shiny Woodoats (Chasmanthium nitidum) is almost entirely found in Florida. The grass barely finds its way into NC where it is considered threatened, being known only from Pender County. 

Chasmanthium latifolium;
the most widespread member of the genus

Scareweed (Baptisia simplicifolia)
Pine Flatwoods, regularly burned
St. Marks NWR, July 2014

One of the Wild Indigos,  or sometimes called "Scareweed", Baptisia simplicifolia is a narrow endemic confined to a couple counties in north Florida's panhandle.

Limited to open pinelands, this is one of the many fire-adapted species found in longleaf pine flatwoods. At the end of the growing season, stems break off above ground and the plant blows around like tumbleweed, helping to distribute seeds still found in the capsules. The vast majority of the world's population is found on the Apalachicola National Forest.


Eurybia eryngiifolia 
Apalachicola National Forest
July 2014
Bristly heads and leaves of Eurybia eryngiifolia

Thistle-leaved Aster (Eurybia eryngiifolia) is nearly endemic to the Florida panhandle, just barely extending into adjacent Georgia & Alabama. It is another pine flatwoods & fire-adapted species, closely associated with longleaf pine.  The scientific epithet (eryngiifolia) is a clear reference to the vegetative similarity to Rattlesnake Master (Eryngium yuccifolium)

Friday, November 7, 2014

Green Silky Scale

Green Silky Scale (Anthaenantia villosa) is a southeastern coastal plain endemic grass species, ranging from eastern Texas to Florida and northward into NC.
A. villosa upright habit and dense, flowering panicle
Note charred longleaf bole and open wiregrass dominated habitat
Image date: Nov 06, 2012

In our area I have observed it only in recently burned longleaf-wiregrass habitats in the inner coastal plain and sandhills regions. Within these generally dry, deep sandy soil sites, the grass occurs in gentle depressions (sometimes called "bean dips") or gentle, almost imperceptibly subtle slopes which are slightly moister than the surrounding uplands.

It occurs in dense swards of grasses where it can be easily overlooked unless flowering. Like a number of other species in these habitats, it may only flower (or at least most profusely) the growing season immediately after burning and may increase as a result. Kush et al. 2000 (in Alabama longleaf pine) documented much greater frequency for this species in biennially burned stands as compared to unburned stands with the greatest frequencies in summer and winter burn units.

Green Silky Scale (foreground), amidst dense wiregrass (Aristida stricta)
Sampson Co., NC (October 20,2011)

Silky Scale clumps turning color in Fall
Nov 06, 2014


Silky scale develops small rhizomatously spreading clumps which appear to expand slowly. Basal leaves are narrow, smooth, and tapering to a narrow tip. According to Grelen & Duvall (1966) leaves are nutritious and palatable forage.

Inflorescences form tight, narrow panicles on upright stems (maybe 3.5' tall) late in the growing season. Individual spikelets are densely pubescent and tightly packed along the upper 8 or so inches of the stem (See image right).


Grelen and Duvall 1966, Common Plants of Longleaf Pine - Bluestem Range, Southern Forest Experiment Station Publication
Kush, J.S., R.S. Meldahl, and W.D. Boyer. 2000. Understory Plant Community Responseto Season of Burn in Natural Longleaf Pine Forests. Tall Timbers Fire Ecology Conference 21:33-39

Flooded Pitchers

Top Image: Mountain Sweet Pitcher (Sarracenia jonesii), Small tubes completely underwater, larger tubes barely emergent
Bottom Image: Purple Mountain Pitcher (Sarracenia purpurea var. montana) , Large rosette completely submerged by flowing water.. 
Both images taken October, 14, 2014.

Previous posts have introduced these Pitcher Plants, which occur on frequently saturated "boggy" substrate. I imagine they are rarely submerged, however, these images document this can happen. This Fall (October 2014), the site experienced a heavy rainfall (approximately 6"), causing an adjacent stream to spill over its banks and directly impact some individuals of both species. Surface water levels receded quickly and the next day there was no standing water remaining.

Both are important conservation targets due to their localized distributions, restricted habitat, very limited numbers of known populations and inherent risk for extirpation. Gaining a better understanding of the hydrology of occupied and historic sites may help us determine ways to permanently protect, and ultimately increase the populations.

Saturday, November 1, 2014

Florida Paspalum - Where o where has it gone?

Florida Paspalum with stigmas and anthers (9/07/14)

Florida Paspalum (Paspalum floridanum) is one of our premier native, warm season grasses. Tall & robust, reaching heights of ~ 5 ', it produces large mature spikelets and seeds. These seeds are (or were) important food sources for quail, doves, and turkeys (Grelen and Duvall 1966).

Ranging throughout most of the lower eastern US, Florida Paspalum occurs and occasionally becomes dominant in a range of high quality, remnant habitats. A few of these include:
  • Florida dry prairies (Orzell & Bridges 2006) 
  • Texas Blackland prairies (Collins et al. what date), 
  • Arkansas & Missouri tallgrass prairies (Ruby 1953, Kelting 1982)
  • Longleaf pine forests & savannas of Georgia (Drew etal. 198), se LA (Roth et al. 2008)) and east Texas (Phillips et al. 2007)
  • Coastal or "cajun" prairies of south Louisiana  (Allen et al. 2001) 
  • Calcareous prairies of Georgia (Echols & Zomlefer 2010), Mississippi (Campbell & Seymour 2011) and Louisiana (Allen et al. 2004)
In Illinois, Verts (1965) found that all (remaining) stands of P. floridanum occurred within 25 yards of railroad rights-of-way, suggesting the sorry state of prairie-like remnants in that state.

In the North Carolina Piedmont, I have observed this species in the only frequently burned longleaf pine forest remaining in the state (near Troy, NC) and in a few remnant burned woodlands near Durham, one of which has been burned biennially for 10 years. It is also found on open roadsides such as the one shown below.

Florida Paspalum (8-13-14) on floristically rich roadside remnant in Granville Co, NC

P. floridanum in biennially burned "savanna" (9/09/13)

At a distance, the young leaves often display a bluish cast, reminiscent of Rattlesnake Master (Eryngium yuccifolium).

This tall grass species occurs with the remnant & disjunct prairie flora under the power-lines known as Picture Creek Diabase Barrens where Stanley (2013) listed it as "infrequent".  Interestingly, P. floridanum is apparently absent from a number of sites where other major prairie grasses are found in the southern Piedmont (Tompkins et al. 2010a, Tompkins 2013), as well as the infamous Suther Prairie (Tompkins et al. 2010b). Perhaps most surprisingly, it was not identified in a recent floristic study of 31 "rural rights-of-way" across the Piedmont (Adams 2012), a study region which including the locations of the pictures included on this page.

As P. floridanum begins to bolt and flower, spikelets emerge seemingly from the midst of the main stem leaves. They eventually overtop the stems but remain tightly arranged around the main stem (left below), later developing much more spreading (3-7 or so) branches (right below).  

P. floridanum bolting (9-07-2014), some nearby inflorescences already spreading
Following images: (left): 8/13/14 Granville Co, NC, (right): 9/07/14 Durham Co, NC

Paspalum floridanum spreading branches have begun to droop (8-23-14),
 note abundant bluish lower leaves in background


Adams, N.S. 2012. A Synthesis of Rights-of-way Native Plant Communities: 
Identifying Their Relevance to Historical and Contemporary Piedmont Savannas. Unpublished MS thesis.
Allen C.M., S. Thames, and L. Chance, and C. Stagg. 2004. Proc. 19th North American Prairie Conference 19-22.
Allen C.M., M. Vidrine, B.Borsari, and L. Allain.  2001. Proc. 17th North American Prairie Conference 35-41.
Campbell, J.J.N., and W.R. Seymour. The Vegetation of Pulliam Prairie, Chickasaw County, Mississippi: a Significant Remnant of Pre-Columbian Landscape in the Black Belt. Journal of the Mississippi Academy of Sciences 56:248-263.
Collins, O.B., F.E. Smeins, D.H. Riskind. Plant Communities of the Blackland Prairie of Texas.
Drew, M.B. L. K. Kirkman, and A. K. Gholson.  The Vascular Flora of Ichauway, Baker County, Georgia: A Remnant Longleaf Pine/Wiregrass Ecosystem. Castanea 63: 1-24.
Echols, L, and W.B. Zomlefer. 2010. Vascular Plant Flora of the Remnant Blackland
Prairies in Oaky Woods Wildlife Management Area, Houston County, Georgia. Castanea 75:78-100
Grelen and Duvall 1966, Common Plants of Longleaf Pine - Bluestem Range, Southern Forest Experiment Station Publication
Kelting, R. W. 1982. The Wah-Sha-She Prairie near Asbury, Jasper County, Missouri. Proc. 8th North American Prairie Conference 80-83.
Orzell & Bridges 2006.  Floristic Composition of the South-Central Florida Dry Prairie Landscape.  Proceedings of the Florida Dry Prairie Conference.
Phillips, T.C., S. B. Walker, B.R. & M.H. MacRoberts. 2007. Vascular Flora of a Longleaf Pine Upland in Sabine County, Texas. Phytologia 89:317-338.
Roth, et al. 2008. How Important is Competition in a species rich savanna. Ecoscience; 94-100
Ruby, E.S. 1958.
Stanley, J. S. 2013. Guide to the Vascular Flora of Picture Creek Diabase Barrens (Granville County, North Carolina). Unpublished MS Thesis.
Tompkins, R.D., W.C. Stringer, K.H. Richardson, E.A. Mikhailova and W.C. Bridges, Jr. 2010a. Big Bluestem (Andropogon gerardii: Poaceae) communities in the Carolinas: Composition and ecological factors. Rhodora 112:378-395.
Tompkins, R.D., C.M. Luckenbaugh, W.C. Stringer,K.H. Richardson, E.A. Mikhailova and W.C. Bridges, Jr. 2010b. Suther Prairie: Vascular flora, species richness and edaphic factors. Castanea 75:232-244.
Tompkins, R.D. 2013. Prairie-relict communities of a Piedmont monadnock. Castanea 78:185-197.
Verts, B.J. 1965. Notes on the ecology of Paspalum floridanum in Illinois. American Midland Naturalist 73

Sunday, October 12, 2014

The Long Awaited Summer (Fire) - Will it save our savannas?

1st Summertime prescribed fire conducted in Brunswick Co, NC
Longleaf Pine relict (right), middle sized trees are mostly Pond Pine
no Longleaf Pine regeneration is present
Vegetation response several weeks later (same site as previous)
Longleaf Pine unfazed but significant needle loss on all Pond Pines 
It has been known for decades that regular or frequent fire facilitates the development of open, grassy longleaf pine (Pinus palustris) savannas. Restoring such conditions in existing longleaf pine stands has become virtual dogma across the southeastern United States. However, relatively few sites actually receive the frequency of fire needed to maintain or recreate open savannas, and even fewer receive fires during the growing season when lightning fires would have occurred historically. This has certainly been the case at the Boiling Spring Lakes Plant Conservation Preserve in Brunswick Co., North Carolina where we have been working, with the help of The Nature Conservancy and the NC Forest Service (NCFS), for approximately 10 years to restore fire prone landscapes.  This summer (2014), the NCFS and our small team conducted the first known summer fire in the region (special thanks to Bill Walker, Shane Hardee, Mike Malcolm & Miller Caison for making the burn a reality)

For decades, typical controlled burns across the southeastern NC and the US occurred during the dormant or winter season.  However, it has been recognized that significant parts of the landscape, especially areas dominated by longleaf pine, developed under eons subject to fires started by lightning. Lightning strikes, especially those most likely to start fires, are mostly associated with summer thunderstorms. In North Carolina July is the peak for these storms (1).                                    

Outcalt (2) showed that the largest, tallest trees were preferentially hit by lightning in longleaf stands. These strikes often leave telltale marks (left), sometimes extending to the ground. In certain cases hot strikes ignite the tree itself and the flammable ground cover nearby (right).

Given dry conditions, available fuels, wind to push the fire, and an unbroken landscape, such lightning ignited fires could have extended for miles.  Large, old longleaf pines tend to have concentrated resins that allow them to burn hot, even when drenched with water. These can easily ignite fires even after the passage of rain fall events.

There is some evidence that lightning season fires produce different ecological effects than fires at other seasons; at least 3 syntheses of these differences have been attempted  (3,4,5).  One benefit is the creation of  "seedbeds" for longleaf pines, which drop their seeds in late Fall.  These seeds (which are produced relatively infrequently, and primarily from older, larger trees) need to access mineral soil and are easily "hung up" in understory grass or shrubs. Ironically, typical winter burns occur almost immediately after seeds have dropped thereby destroying many seed crops. Therefore, managing longleaf stands with regular winter fires could eliminate regeneration of the dominant trees. Further, non-lightning season fires (especially if infrequent as they are in most areas) tend to favor development of dense shrub stems which may further hinder longleaf regeneration.

A perfect seed bed for longleaf pine seeds to establish

Serotinous Pond Pine Cone
Immediately after fire
Serotinous Pond Pine Cone
Just opened after fire
In contrast, Pond Pine (Pinus serotina) produces much smaller seeds, produces them at much younger ages, and holds them on the tree for several years until hot fire opens them.

Fires during any season, including winter, could potentially heat the serotinous cones and cause seeds to drop into freshly prepared seed beds.  Pond Pine also has the capability to reprout after even intense fires that could kill similar sized longleaf pines.  Taken together, these factors provide an environment where tree dominance shifts from longleaf pine to pond pine.

Pinus serotina resprouting after summer fire;
in addition to "main" epicormic sprout there are 3 others emerging (front right, back left)
Several previous stems (now blackened and top killed) were present from previous fire
Savanna in Brunswick Co., NC with a rare regenerating Longleaf pine (foreground) amidst taller saplings of Pond Pine
larger trees (rearground) are also Pond Pine

BELOW: Longleaf Savanna replaced by Pond Pine Flatwoods
Lone Pinus palustris persists near middle; dense shrub layer has developed

Longleaf pine relict indicating previous stand composition and open structure
One fire reduced some immediately adjacent & "invading" Pond Pine stems but
high fuel loads remain and threaten remaining Longleaf

BELOW: Longleaf Pine stand decimated by wildfire after heavy midstory development as in previous image;
standing dead are longleaf pines,Pond Pine present were killed and have not reemerged into midstory or overstory
dense tall shrub layer is still present

Although growing season fires are often thought to be important for various ecological reason one of the most important, yet least understood, may be the reversal of longleaf pine savanna replacement from dense, flammable stands of Pond Pine.  

(2) Outcalt, K. 2008. Lightning, fire and longleaf pine: Using natural disturbance to guide management. Forest Ecology and Management 255.
(3) Robbins, L.E. and R.L. Myers. 1992. Seasonal effects of prescribed burning in Florida: a review. Tall Timbers Research Station. Misc. Publ.
(4) Streng, etal. 1993. Evaluating effects of season of burn in longleaf pine forests: a critical literature review and some results from an ongoing long-term study. Proceedings Tall Timbers Fire Ecology Conference 18.
(5) Knapp etal. 2009. Ecological effects of Prescribed Fire Season: A Literature Review and Synthesis for Managers. USDA General Technical Report PSW-GTR-229.

Wednesday, October 8, 2014

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

Sunday, September 14, 2014

Beech Blight

American Beech (Fagus grandifolia) is a common and distinctive tree found across much of eastern North America. It is most often found on moist, acidic sites where it grows slowly, but lives long as a component of late successional, minimally disturbed forests.  

The smooth, silver bark gives American beech an almost elegant appearance compared to rough barked species it is often associated with.  However, this bark is quite thin and makes the tree susceptible to a variety of "damaging agents" (1).

Careful observation during the late summer & early fall may reveal signs of one of the more unusual of these "damaging agents".  There are at least 4 different but closely related signs to look for.  The first of these symptoms is defoliation or apparent die-off of limbs, usually evident on the lower branches, prior to normal leaves turning color or shedding.
Extensive defoliation of lower limbs; no living leaves present on the lower third of the trunk

In extreme cases, like the tree shown above, all lower limbs may be barren of live leaves. More commonly, only a single limb or two may be affected. Sometimes the culprit can be found in the process of causing defoliation on twigs that appear to be covered in a dense white, cottony fuzz. The fuzz is actually hundreds or thousands of colonial aphids. When approached closely, they wave and gyrate possibly as a defensive mechanism.  

The aphids (Grylloprociphilus imbricator) feed by sucking sap from the living beech tissue (possibly aided by the thin bark). Each colony includes individuals of different developmental stages or "instars". For example, on the image above, both winged and non-winged individuals can be observed as well as some individuals with varying degrees of plumage emanating from the rear abdomen (the later generations).  
Splotch of black tar-like material indicating feeding of aphids 

One of the many insect visitors feeding on aphid residues
As they feed, the aphids deposit "honeydew" or excrement on surfaces below. This honeydew begins to be colonized by sooty molds that give the appearance of black liquid tar. These patches are easy to spot and often persist for at least 2 seasons. 

The honeydew provides an attractant to numerous insects (see image left). For unknown reasons, possibly the quantity of honeydew, some substrates develop dense masses of sooty molds not just thin black films. 
Sooty Mold (probably Scoriosa spongiosa) in early development on Fagus leaf
Sooty Mold in later development on Fagus leaf
Sooty Mold mass on American Beech twigs

Sooty Mold mass advanced growth on Beech twigs

The sooty molds apparently don't penetrate leaves but dense patches seem to be able to limit or completely block photosynthesis.  Not surprisingly, tree seedlings underneath aphid colonies suffer greater mortality than unaffected seedlings (2).  I have observed several herbaceous and shrub species being negatively affected in this way, including Hepatica, Christmas Fern, and Mountain Laurel. 

This process could account for the relative lack of other species of plants around some American Beech stems (see image at top of page). 


(2) Cook-Patton. S.C., L. Maynard, N.P. Lemoine, J. Shue, and J.D. Parker.  2014. Cascading effects of a highly specialized beech-aphid-fungus interaction on forest regeneration. PeerJ.