Canadian fleabane (Conyza canadensis) is a plant belonging to the Asteraceae family. Some texts refer to it as Erigeron canadensis, while it is commonly known as Canadian fleabane or simply fleabane and conyza. It grows wild throughout Italy, including the islands, and due to its ease of spread, it is considered a weed in cultivated fields. However, not everyone is aware that this plant possesses medicinal properties that can be easily utilized in home herbalism.
In this article, we will explore the botanical characteristics of Conyza canadensis, its active principles, properties, and common uses.
Description of Canadian Fleabane
Conyza canadensis is an herbaceous plant with an annual or biennial life cycle, characterized by the biological form of a scapose therophyte. It has a long fibrous root system from which basal rosettes of leaves emerge, followed by the stems. These stems can grow up to 1-1.5 meters in height. The entire surface of the plant is covered in fine hairs.
The leaves of Canadian fleabane do not have well-defined petioles but are mostly tapered at the base. Some of the upper leaves may be sessile. The lower leaves are lanceolate, while the others are very narrow and linear, with margins that can be entire or serrated. Long, bristly hairs are also present on the leaves, particularly along the central vein and the margins.
The inflorescence of Erigeron canadensis is a large, highly branched terminal panicle. The flowers are grouped in small heads: the outer ones have small white or pinkish ligules, while the others are yellowish. Canadian fleabane has an extended flowering period, spanning from spring to autumn.
The fruit of Conyza canadensis is an achene (seed) covered with short hairs and topped by a pappus composed of numerous white to yellowish bristles. The pappus aids in the wind-mediated dispersion of seeds.
Where Canadian Fleabane Grows
As suggested by its botanical name, Erigeron canadensis is native to North America and has spread to various parts of the world. In Italy, it has been naturalized since the 17th century and can be found in fallow fields, gardens, cultivated fields, riverbanks, and ruderal areas. It seems to have spread primarily because it grows along roadsides and in gravelly areas along railways. The “wind” generated by passing vehicles helps carry the pappus containing the seeds over long distances. It is present from the Mediterranean region to mountainous areas. It is considered an invasive plant in intensive cultivation and pastures, partly because animals avoid eating it due to its bitter taste. Another unique feature is that Canadian fleabane is perfectly resistant to glyphosate-type herbicides, which have no detrimental effect on the plant.
Useful Parts and Harvesting
In herbalism, the useful parts of Conyza canadensis are the flowering tops, including the stems and leaves. Harvesting is done in spring or summer when the plant is in the early stages of flowering. The flowering tops, along with about ten centimeters of the stem, are cut for collection. The harvested parts are tied into loosely packed bundles and hung to dry in a well-ventilated and shaded area. Once dried, the bundles can be stored in paper bags.
Active Principles of Canadian Fleabane
The primary constituents of Canadian fleabane include essential oil (citronellol, limonene etc), phytosterols, flavonoids, resins, and tannins.
Properties of Canadian Fleabane
The beneficial properties of Conyza canadensis are primarily attributed to the presence of essential oil. This oil imparts both a characteristic odor and a slightly bitter taste to the decoctions while providing balsamic and anti-inflammatory virtues to the respiratory system. However, Canadian fleabane is primarily known for its antidiarrheal, diuretic, and depurative properties. It is especially useful for rheumatic, arthritic, and gouty conditions, as it aids in the elimination of nitrogenous waste from the body through increased urine secretion. For external use, Erigeron canadensis can be employed in decoctions to soothe irritations and mild ulcerations of the mouth and throat.
At home, Canadian fleabane decoction is prepared using different dosages depending on whether it is for internal or external use. For internal use, 2 grams of dried plant material are used in 100 ml of water, to be consumed in 2-3 small cups per day. For external use, 6 grams are used in 100 ml of water for rinsing and gargling.