American burnweed | skymeadows

Habit: Annual herb, 300 cm tall, with erect stem, more or less strongly ribbed (grooved), simple or branched toward the top, glabrous to villose with translucent hairs.

Leaves: The leaves are highly variable in size and shape. The base may be attenuate to a distinct petiole, broadly sessile, or expanded and clasp-

ing to auriculate. Several leaf forms are often visible on the same plant and those with clasping or auriculate bases tend to be larger toward the middle of the stem.

Leaves are alternate, the lower (3) 620 cm long (1) 28 cm wide and diminishing in size upwardly, mostly glabrous or margins ciliate with short hairs and lower surface usually also with longer hairs (especially along the principal veins), irregularly toothed and lobed, with secondary veins extending to the marginal gland-tipped teeth; lower leaves elliptic

to broadly lanceolate, shallowly toothed to weakly acute lobed, usually weakly petiolate; middle to upper leaves lanceolate, acute, irregularly toothed, often deeply acute lobed, sessile or clasping at the base, with distal leaves bract-like.

Flowers: The upper stems terminate in panicles of flowerheads. A flowerhead consists of numerous tubular disk florets, which are enclosed by green bracts that are smooth and linear. Sometimes these bracts assume a purplish appearance. The corollas of the disk florets, which are barely visible above the bracts, are white. The outer florets are fertile and pistillate, while the inner florets are hermaphroditic or sterile. The flowerheads are about ¾" long and ¼" across; they are slightly wider at the base, where there may be some outer bracts that are very short and linear.

Fruit/Seed: As is typical in the Asteraceae, the dispersal unit is a cypsela, defined as a type of fruit formed from a single-seeded inferior ovary. The naked seeds are mostly dark blue to blackish with a whitish zone at the base.

Roots: Thee root system consists of a taproot with shallow, fibrous secondary roots.

REGENERATION PROCESS: American burnweed propogates itself

by reseeding, dispersing seeds by air.

HABITAT TYPES: American burnweed prefers Anthropogenic (man-made or disturbed habitats), brackish or salt marshes and flats, coastal beaches (sea beaches), meadows and fields, wetland margins (edges of wetlands). Population explosions may occur in these habitats (par-

ticularly after human induced disturbances) and other conditions where competition is reduced, but generally subside rapidly with succes-

sional progression to less open environments. Shores of lakes and rivers, habitats characterized by natural disturbance, are common locations for American burnweed as are sites associated with beaver activities causing cyclical flooding and drainage. It is found in a wide range of anthropogenic habitats where vegetation is regularly disturbed or main-

tained at early successional stages, such as roadsides, railway lines, ditches, energy corridors, quarries, tree plantations, cultivated land, turf, flower beds, or ruderal sites.

SITE CHARACTERISTICS: American burnweed prefers places receiving some direct sunlight such as openings, edges, or along trails. The predominant soil types in eastern mixed forest areas where American burnweed appears following fires or forest clearance are loams and silt loams originating from acid shales, sandstones and lime-

stones, often acidic with an average soil pH of about 4.5. In the wetland complex of the Delaware River (NJ), American burnweed was found in

shrub forest habitats on alluvial and aeolian deposits.

SEASONAL DEVELOPMENT: The blooming period occurs during late summer or early fall for about a month.

GENERAL DISTRIBUTION: In North America, American burnweed

is found primarily in deciduous forest regions of eastern Canada from the Maritime Provinces to western Ontario, and in the United States from New England west to Minnesota in the north, and south to Florida and

eastern Texas. It has also been reported as sporadically occuring in the Pacific coast states.

SKY MEADOWS DISTRIBUTION: To be determined.

IMPORTANCE AND USES: Primarily wasps visit the flowers for nectar, including Paper wasps, Hornets, Eumenine wasps, and Spider wasps. Other insect visitors include long-tongued bees, short-tongued bees, and Tachinid flies. The Chinese ladybeetle, Leis conformis, imported into Florida to combat the green citrus aphid, Aphis spiraecola,

has been found feeding on the blossoms of American burnweed; al-

though entire blossoms including stamens and pistils were eaten, no

larvae, pupae or eggs were observed. Larvae of Palthis asopialis are reported to feed on American burnweed. Larvae of Tyria jacobaeae

(Arctiidae), a biological control agent against Senecio jacobaea,

were reported to feed and mature on American burnweed in forced feeding trials.

Outside North America, several species of moths have been reported

to include American burnweed in their host range, including Hypercompe icasia (Arctiidae), Platyptilia molopias (Pterophoridae),

and Platphalonidia subolivacea (Tortricidae). Evidence of leaf-mining insects is not uncommon on herbarium specimens of Amerian burnweed.

The microlepidoptera Phyllocnistis insignis (Gracillariidae) has been reported on American burnweed.

In south Florida, American burnweed is among the many species of Asteraceae suitable as hosts for the leaf miner fly Phytobia maculosa (Agromyzidae), whose larvae form large blotch mines on the leaves. In

the vicinity of vegetable crops in Florida, the highly polyphagous serpentine leaf miners Liriomyza sativae (Agromyzidae) are found on

American burnweed. In Taiwan, American burnweed was found to be a preferred host of the leafminer Liriomyza trifolii and whie none of these

leaf-mining flies occur in the field, the latter is a pest of greenhouse crops.

American burnweed is host to the tarnished plant bug, Lygus lineolaris (Heteroptera: Miridae) and a gall midge, Neolasioptera sp. (Diptera: Cecidomyiidae), has been reported in Florida, causing irregular stem swellings 25 cm long. A flower-head gall produced by Asphondylia sp.

(Cecidomyiidae) has been reported and infestation by the cosmopolitan

aphid species Brachycaudus helichrysi (Homoptera: Aphididae) has been found on Amerian burnweed in Florida. In addition, a carabid beetle (Anisodactylus terminatus) has been observed feeding on ripening

seeds of American burnweed.

No reports have been found indicating whether the bitter leaves with their unpleasant odour are palatable to mammals and there is insufficient information as to the palatability of American burnweed to birds and other vertebrates.

As a medicinal plant in North America, the use of American burn-

weed has had a complex and confusing history. Ninteenth century authors indicated that ‘‘fireweed oil’’ of North American commerce was usually derived from other species (not Erechtites hieraciifolius), but maintain that American burnweed oil had distinct benefits. A number of early North American sources indicate medicinal uses of the plant in treatment for haemorrhage, wounds, skin diseases, dysentery, cholera,

and as a purgative and emetic. Algonquin native peoples treated poison ivy (Toxicodendron radicans) and poison sumac (Toxicodendron vernix)

poisoning. Ninteenth century sources recommended American burn-

weed's use in the treatment of dysentery, menstrual disorders and gonorrhoea; others considered the plant’s volatile oil to be the principal active ingredient in a tincture produced from whole fresh flowering plants for use as an emetic and in treatment of such conditions as eczema, diarrhoea, haemorrhages and piles, but noted that nausea and other adverse reactions could result from use of this tincture. In the early 20th century its use as a medicinal herb was sufficiently popular that collectors were paid 23 cents per pound.

Many authors comment on the unpleasant or rank odour of the plant. In spite of this, it has been sggested that Amrican burnweed can be used as a salad or potherb. The plant’s odour does not seem to be consistently distasteful to all people.

In the Andes of South America the leaves and flowers of variety cacalioides have been used in folk medicine as a blood depurative and the roots to treat cardiac disease.

American burnweed has been used as a source of a blue dye for cotton and wool.

American burnweed has been found to be among the most efficient of the plants tested at assimilating atmospheric nitrogen dioxide (NO2) with as much as 10% of its total organic nitrogen content derived from this source. Such plants have the potential to act as important sinks for

anthropogenic nitrogen oxides. Japanese researchers have proposed that

‘‘green walls’’ using such nitrogen dioxide-philic plants could be set up around buildings and on highway corridors to help sequester pollutants from car emissions or other sources.

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