Poor Fen

Ecology and Physical Setting 

If you’re going to visit a Poor Fen, prepare to get your feet wet. In the continuum of peatland types, Poor Fens are closely related to Dwarf Shrub Bogs, but Poor Fens are wetter and typically have water levels at or near the surface of the hollows for much of the growing season. These open peatlands are dominated by sphagnum mosses, sedges, and heath shrubs. Poor Fen waters are acidic, but unlike bogs, they are slightly enriched by ground or surface water, which delivers a low concentration of dissolved minerals to the fen surface. Vegetation of the moist hollows reflects this mineral enrichment. In contrast, the tallest hummocks stand one to three feet above the water in the hollows and may be completely ombrotrophic, receiving water and nutrients entirely from precipitation. Water squeezed from sphagnum at a hummock top may have a pH near 3.5, whereas water in an adjacent hollow typically has pH ranging from 5.0 to 5.5. 

Poor Fens occur in a variety of physical settings, from small isolated basins to large wetland complexes that may be associated with streams. They generally have deep peat made up of poorly decomposed sphagnum and some sedge and woody material. They also occur as floating peat mats, growing out over the open water of small acidic ponds. Poor Fens commonly occur with Dwarf Shrub Bogs or Black Spruce Woodland Bogs, but may grade into other peatland types as well. 

Vegetation 

The well-developed hummocks of most Poor Fens are very similar to those found in Dwarf Shrub Bogs. There is a complete cover of sphagnum, with the typical zonation from hummock top to hollow bottom being Sphagnum fuscum, Sphagnum capillifolium, Sphagnum magellanicum, Sphagnum angustifolium, and Sphagnum fallax. A sparse cover of heath shrubs is present on the hummocks, with leatherleaf and bog rosemary especially common, and lesser amounts of bog laurel, Labrador tea, and sheep laurel. Stunted black spruce, tamarack, and red maple may be scattered on the widely spaced hummocks. Small cranberry, Billings’ sedge, few-flowered sedge, hare’s tail cottongrass, pitcher plant, and round-leaved sundew are all common on the hummocks.

The hollows in Poor Fens are larger and wetter than those in Dwarf Shrub Bogs, and typically contain standing water for much of the growing season. The species in these wet hollows indicate the increased enrichment as compared with Dwarf Shrub Bogs. Mud sedge and white beakrush are common, along with bog-bean, tawny cottongrass, large cranberry, and spatulate-leaved sundew. The uncommon rose pogonia and the rare pod-grass are highly characteristic of Poor Fens. 

Two types of wide moist “lawns” can be found in Poor Fens. In one, the honey-brown Sphagnum papillosum forms a carpet, typically scattered with sweet gale, leatherleaf, white beakrush, and large cranberry. In the other, the bright red Sphagnum rubellum forms a carpet scattered with bog rosemary, leatherleaf, white beakrush, and small cranberry. Black-green, flat “mud bottoms” can occur in hollows and are dominated by the liverwort Odontoschisma fluitans.

Wildlife Habitat

Although small in total area, Poor Fens support an astonishing assortment of animals. A combination of factors, including openess, saturated moss, and standing water in hollows or associated small peatland ponds, makes these wetlands especially important wildlife habitat. Green frogs—and, in the northeastern part of Vermont, mink frogs—can be found in a variety of wetlands including Poor Fens. Four-toed salamanders lay their eggs in moist sphagnum and may breed in permanent fen pools in warmer regions. 

Breeding birds of Poor Fens include Lincoln’s sparrow, common yellowthroat, Nashville warbler, and Wilson’s snipe. The rare ring-necked duck and the uncommon American black duck both build their nests on hummocks close to open water.

Dragonflies, damselflies, and butterflies can be abundant in Poor Fens. Among the dragonflies are the uncommon elfin skimmer and the rare, aptly-named ebony boghaunter. Other dragonflies include several species of emeralds and whitefaces. The widespread boreal bluet, and the rare sphagnum sprite and subarctic bluet, are some of the damselflies found in Poor Fens. Two of the rare butterflies found in Poor Fens rely on heath-family shrubs as host plants—bog copper caterpillars feed exclusively on cranberries, and brown elfin caterpillars feed on blueberries, huckleberries, and leatherleaf.

Related Communities 

• Dwarf Shrub Bogs are dominated by sphagnum and heath shrubs and are ombrotrophic, receiving most of their water and nutrients from precipitation. Dwarf Shrub Bogs lack the mineral enrichment indicators found in Poor Fens. 
  
   
• Intermediate Fens are mineral-enriched peatlands dominated by woolly-fruited sedge and sweet gale, with abundant brown mosses. Sphagnum and heath shrubs are uncommon, except on hummocks. 

Conservation Status and Management Considerations 

Poor Fens are rare in Vermont, and most of our examples are small. Several high-quality examples are protected. As with other wetland communities that receive nutrients and minerals from ground or surface water, Poor Fens are threatened by land use changes that occur within both their immediate watersheds and within their groundwater recharge zones. Protecting the quality and quantity of water that reaches a fen is critical to maintaining the hydrology and the vegetation structure and composition of the community. 

Distribution/Abundance 

Poor Fens are rare in Vermont but are widely distributed across the state. Poor Fens are found from the northern Lake States to New England and north into Canada.

Characteristic Plants

Trees (stunted)

Occasional Species

Black spruce – Picea mariana

Tamarack – Larix laricina

Red maple – Acer rubrum

Shrubs

Abundant Species

Leatherleaf – Chamaedaphne calyculata

Bog rosemary – Andromeda polifolia

Small cranberry – Vaccinium oxycoccos

Occasional to Locally Abundant Species

Bog laurel – Kalmia polifolia

Labrador tea – Rhododendron groenlandicum

Sheep laurel – Kalmia angustifolia

Black chokeberry – Aronia melanocarpa

Large cranberry – Vaccinium macrocarpon 

Herbs

Abundant Species

Mud sedge – Carex limosa

White beakrush – Rhyncospora alba

Occasional to Locally Abundant Species

Bog-bean – Menyanthes trifoliata

Tawny cottongrass – Eriophorum virginicum

Spatulate-leaved sundew – Drosera intermedia

Horned bladderwort – Utricularia cornuta

Billings’ sedge – Carex billingsii

Few-flowered sedge – Carex pauciflora

Hare’s tail cottongrass – Eriophorum vaginatum

Pitcher plant – Sarracenia purpurea

Round-leaved sundew – Drosera rotundifolia

Bryophytes

Abundant Species

Moss – Sphagnum capillifolium

Moss – Sphagnum rubellum

Moss – Sphagnum magellanicum

Moss – Sphagnum angustifolium

Moss – Sphagnum fallax

Occasional to Locally Abundant Species

Moss – Sphagnum papillosum

Moss – Sphagnum flexuosum 

Moss – Sphagnum fuscum

Moss – Sphagnum cuspidatum

Moss – Sphagnum majus

Liverwort – Odontoschisma fluitans

Rare and Uncommon Plants

Pod-grass – Scheuchzeria palustris

Bog sedge – Carex exilis

Water sedge – Carex aquatilis var. substricta

Creeping sedge – Carex chordorrhiza

Dragon’s mouth – Arethusa bulbosa

Grass pink – Calopogon tuberosus

Rose pogonia – Pogonia ophioglossoides

Bog bedstraw – Galium labradoricum

Bog willow – Salix pedicellaris

Northern yellow-eyed grass – Xyris montana

Bog aster – Oclemena nemoralis

Atlantic sedge – Carex atlantica var. atlantica 

Northeastern sedge – Carex cryptolepis 

Michaux’s sedge – Carex michauxiana 

Few-seeded sedge – Carex oligosperma 

Twig rush – Cladium mariscoides 

Marsh willow-herb – Epilobium palustre 

Rough cottongrass – Eriophorum tenellum 

White fringed orchis – Platanthera blephariglottis 

Hidden-flowered bladderwort – Utricularia geminiscapa 

Lesser bladderwort – Utricularia minor 

Mountain fly honeysuckle – Lonicera villosa 

Rough-leaved aster – Eurybia radula 

Moss – Sphagnum lindbergii

Moss – Sphagnum pulchrum

Associated Animals

Green frog – Lithobates clamitans

Red-bellied snake – Storeria occipitomaculata 

Lincoln’s sparrow – Melospiza lincolnii 

Common yellowthroat – Geothlypis trichas 

Nashville warbler – Oreothlypis ruficapilla 

White-throated sparrow – Zonotrichia albicollis

Swamp sparrow – Melospiza georgiana 

Alder flycatcher – Empidonax alnorum 

Wilson’s snipe – Gallinago delicata 

Mallard – Anas platyrhynchos 

Boreal bluet – Enallagma boreale 

Brush-tipped emerald – Somatochlora walshii 

Clamp-tipped emerald – Somatochlora tenebrosa

Canada darner – Aeshna canadensis

Four-spotted skimmer – Libellula quadrimaculata 

Hudsonian whiteface – Leucorrhinia hudsonica

Frosted whiteface – Leucorrhinia frigida 

Belted whiteface – Leucorrhinia proxima

Rare and Uncommon Animals

Mink Frog – Lithobates septentrionalis

Four-toed salamander – Hemidactylium scutatum

Spotted turtle – Clemmys guttata 

Smooth greensnake – Opheodrys vernalis

Southern bog lemming – Synaptomys cooperi 

Ring-necked duck – Aythya collaris

American black duck – Anas rubripes 

Bog copper – Lycaena epixanthe

Brown elfin – Callophrys augustinus

Jutta arctic – Oeneis jutta

Two-spotted skipper – Euphyes bimacula 

Kennedy’s emerald – Somatochlora kennedyi

Ocellated emerald – Somatochlora minor

Forcipate emerald – Somatochlora forcipata

Delicate emerald – Somatochlora franklini

Ebony boghaunter – Williamsonia fletcheri

Elfin skimmer – Nannothemis bella

Sphagnum sprite – Nehalennia gracilis 

Harlequin darner – Gomphaeschna furcillata

Subarctic darner – Aeshna subarctica

Subarctic bluet – Coenagrion interrogatum

Petite emerald – Dorocordulia lepida

Places to Visit 

Dennis Pond, West Mountain Wildlife Management Area, Brunswick, Vermont Fish and Wildlife Department (VFWD)



Steam Mill Brook Wildlife Management Area, Walden, VFWD



Fairfield Swamp Wildlife Management Area, Fairfield and St. Albans, VFWD



Cranberry and Walker Swamps, Pond Woods Wildlife Management Area, Benson and Orwell, VFWD



Branch Pond, Sunderland, Green Mountain National Forest