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Plants of the Eloise Butler Wildflower Garden

The oldest public wildflower garden in the United States

Burnweed

Common Name
Burnweed (American Burnweed, Fireweed, Pilewort)

 

Scientific Name
Erechtites hieracifolius (L.) Raf. ex DC. var. hieracifolius

 

Plant Family
Aster (Asteraceae)

Garden Location
Upland/Woodland

 

Prime Season
Late Summer to Autumn Flowering

 

 

Burnweed is a native, erect annual forb, growing on stout green stems from 2 to 8 feet high. Stems have fine ridges, darker green vertical lines and sparse white hair or can be hairless. It is unbranched beneath the inflorescence.

The leaves are both basal and stem. Basal being larger and usually with a short stalk. Stem leaves are stalkless or may have a auricle partly clasping the stem. Leaves have a pinnate vein pattern. The blade is mostly ovate to lanceolate with lobes and coarse pointed teeth on the lobes. Some upper leaves may be entire. The lower surface has fine hair and sparse longer hair on the veins. The upper surface is usually smooth but may have some fine hair. The foliage is not succulent and has a pungent odor when crushed and a bitter and acrid taste.

The inflorescence is a terminal panicle and auxiliary panicles from the upper leaf axils, the entire group forming a pyramid shape. Each panicle cluster is somewhat flat-topped.

The individual flowers are cylindric, only 1/4 inch wide but about 3/4 inches long. The outside of the head has 1 to 2 series of erect phyllaries, equal in size, linear to lanceolate in shape, with fine darker green vertical lines and purplish tinges. These usually number 21. Some yellow-green linear bracts may be at the base of the flowerhead. The flowers are disc florets of two types. There are no ray flowers. An outer band of florets are fertile and pistillate only. They have whitish to pale yellow corollas with 4 to 5 erect lobes. These surround a smaller group of disc florets that are mostly bisexual and fertile but sometimes are simply staminate in function. These have corollas of similar color with 4 to 5 erect to spreading lobes. The corollas of the disc florets seldom reach above the height of the green phyllaries of the flowerhead. Styles are branched at the tip. The base of the flowerhead swells prior to flowering.

Seed: Fertile flowers produce a obovoid shaped dry cypselae (like an achene) 2.3 to 3 mm long with 10 to 12 nerves on the face. These have a white fully pappus at the larger end for wind dispersion.

Varieties: See notes below the photos.

 

Habitat: Burnweed grows from a shallow fibrous root system with a short taproot and is found in sunny disurbed areas where it grows best. It will also grow in part shade in open woods. Dry to wet conditions are tolerated.

Names: The genus Erechtites is believed to be an ancient name, as far back as Dioscorides, for a plant with similar characteristics. The species hieracifolius means 'leaves like Hieracium' which are the Hawkweeds. As to the many common names - the importance of scientific names is realized here. USDA and the University of MN Herbarium use American Burnweed, whereas the MN DNR Uses Pilewort. The older name 'Fireweed' appears in Flora of North America and Britton and Brown. The name 'Fireweed' is normally applied to Epilobium angustifolium, but like E. angustifolium, the name has been applied here (as has 'Burnweed') because of the belief that it quickly colonizes newly burned areas. Thoreau, among others, disputes this; see his comments below.

The author names for the plant classification are: First to classify was '(L.)' which refers to Carl Linnaeus (1707-1778), Swedish botanist and the developer of the binomial nomenclature of modern taxonomy. His work was updated first by ‘Raf.’ which is for Constantine Samuel Rafinesque, (1783-1840), European polymath who traveled in the United States, lived here many years, collected specimens, and published over 6,700 binomial names for plants. He applied to be botanist on the Lewis & Clark expedition but Jefferson turned him down in favor of training Lewis to act as botanist and saving the expense of another person. His work was corrected by ‘DC’ who is Augustin Pyramus de Candolle (1778-1841), Swiss botanist, who influenced Charles Darwin. He studied plants, began a systematic catalogue and has 2 genera named for him.

See bottom of page for notes on the Garden's planting history, distribution in Minnesota and North America, lore and other references.

Burnweed drawing

Above: The branched inflorescence with heads in various states of maturity. Drawing from Britton, N.L., and A. Brown. 1913. An illustrated flora of the northern United States, Canada and the British Possessions. 3 vols. Charles Scribner's Sons, New York.

Below: 1st photo - Note the linear phyllaries with a darker green stripe and the small bracts under the flower head.2nd photo - Of the two types of disc flowers, the inner ones have erect to spreading corolla lobes. Styles branch near the tip.

Flower cluster flower

Below: 1st photo - The plant is bushy with many leaves.2nd photo - Stems have dark green vertical lines and can have whitish hair. Upper leaves have small auricles that clasp the stem. 3rd photo - The inflorescence has one to several branched panicles.

Full plant Stem Inflorescence

Below: The larger lower leaf has a short stalk, lobed margins with teeth.

leaf

Below: 1st photo - The underside of the leaf is paler color with whitish hair on the veins. 2nd photo - dry seeds have a fluffy white pappus. 3rd photo - the root system is shallow and fibrous with a short taproot.

leaf underside Seed head root

Notes:

Notes: Burnweed is considered to be indigenous to the Garden area. Martha Crone referred to it as 'Fire-weed' in her 1951 Garden Census. Burnweed is found in the eastern 2/3rds of the U.S. plus it is found along the west coast. In Canada it is know in Ontario, Quebec, New Brunswick, Nova Scotia and Prince Edward Island. Within Minnesota it is somewhat limited, mostly found in a group of counties from the north metro north to Todd, Crow Wing and Pine, then south along the Mississippi. Some south metro counties such as Carver and Dakota do not report it. This is the only species of Erechtites in Minnesota. There are two other species in North America.

Varieties: There are 2 accepted varieties of Erechtites hieracifolius - var. hieracifolius and var. megalocarpus. The former is the variety known in Minnesota and is described above. Var. megalocarpus has succulent leaves and the cypselaeare 4–5 mm long with nerves of 16–20. It is found only on the east coast of the U.S. Some references list a few other varieties but Flora of North America does not accept them for North America.

Uses: In some areas the young tops and foliage are eaten as salad or as a potherb. As Fernald (Ref.#6) wrote: "There is no reason, except the odor, to prevent our using it. Cooking may make it palatable to us." He use of 'may' indicates he obviously had not tried it. Hutchins (Ref.#12) reports that the root was used medicinally for purifying the system in blood diseases and discharges. It is said to be unrivaled for an accumulation of mucus such as in colds, allergies, etc. One large teaspoon of finely chopped root and foliage, placed in a cup of boiling water for 1/2 hour provided a tonic to be drunk. Tinctures with alcohol were also made. Grieve (Ref.#7) reports that the plant makes a volatile oil - oil of Erechtites, which is obtained by distilling the plant with water and that this distillation was used for treating piles (hence one of the other common names) and dysentery. The tincture made with alcohol had a clear reddish-orange color but a bitter taste.

Thoreau wrote about the plants commonly named "fireweed" (Epilobium angustifolium and Erechtites hieracifolia, ): "However those are not with very peculiar fitness called fireweeds for they spring up in the same manner on new land when it is laid bare by whatever cause, hereabouts as often after a cutting as after a burning, though I will not deny that the ashes may be a good manure for them. Their localities with us are recently cleared, gravelly, and bare spots in sproutlands. There are enough of these seed in the air always ready to fall on and vegetate in such places. "

"The Erechtites hieracifolia is the plant which is most commonly believed to be spontaneously generated, it not being notice till a clearing is made (which is done by burning) [Ed note: Or by personal observation - by removing dense shrub growth] and then it springs up densely; but as far as my observation goes, it is quite generally distributed through our woodlands, though it is comparatively rare and puny in the dense wood. It is like the thistle in its fruitfulness and volatility Millions of these seeds may be blown along the very lane in which we are walking without our seeing one of them."

References and site links

References: Plant characteristics are generally from sources 1A, 32, W2, W3, W7 & W8 plus others as specifically applied. Distribution principally from W1, W2 and 28C. Planting history generally from 1, 4 & 4a. Other sources by specific reference. See Reference List for details.

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