Botanical Overview
Black Alder (Alnus glutinosa) belongs to the Betulaceae family. While not among the most extensively documented medicinal plants, this species has recorded uses that warrant attention from researchers and practitioners. The birch family (Betulaceae) includes trees and shrubs with simple, alternate leaves with serrated margins and prominent stipules. The flowers are arranged in catkins, and the fruits are small nuts or samaras. The bark of many species contains phenolic compounds with antiseptic properties.
General Description
It thrives in wet locations where its association with the bacterium Frankia alni enables it to grow in poor quality soils. It is a medium-sized, short-lived tree growing to a height of up to 30 metres (98 feet). It has short-stalked rounded leaves and separate male and female flowers in the form of catkins. The small, rounded fruits are cone-like and the seeds are dispersed by wind and water. The common alder provides food and shelter for wildlife, with a number of insects, lichens and fungi being completely dependent on the tree. It is a pioneer species, colonising vacant land and forming mixed forests as other trees appear in its wake. Eventually common alder dies out of woodlands because the seedlings need more light than is available on the forest floor. Its more usual habitat is forest edges, swamps and riverside corridors. The timber has been used in underwater foundations and for manufacture of paper and fibreboard, for smoking foods, for joinery, turnery and carving. Products of the tree have been used in ethnobotany, providing folk remedies for various ailments, and research has shown that extracts of the seeds are active against pathogenic bacteria.
Family Context
The Betulaceae family is widely distributed in the Northern Hemisphere. Notable medicinal members include:
- Alnus rubra — 20 documented uses
- Betula alba — 17 documented uses
- Cherry Birch — 16 documented uses
- Alnus rugosa — 5 documented uses
Geographic Distribution
Black Alder has been recorded in 10 countries and territories worldwide, including Belgium, Germany, Denmark, Spain, Finland, and others.
Traditional Uses
Black Alder has been traditionally used for digestive health, urinary tract health, and fever management, among other applications.
Digestive health.
- Vermifuge
For digestive complaints, the herb is typically prepared as a tea or decoction taken before meals. The bitter compounds stimulate digestive secretions and improve nutrient absorption. Some traditions use the powdered root or leaves in small doses as a stomachic tonic.
Urinary tract health.
- Diuretic
Urinary tract applications typically involve drinking the herb as a mild tea, which increases urine production and helps flush the urinary system. It may be combined with other demulcent herbs to soothe irritated tissues.
Fever management.
- Fever
Febrifuge preparations are typically administered as hot teas to induce perspiration, which helps the body regulate temperature. The patient is kept warm and encouraged to rest while the herb promotes sweating.
Active Compounds
Phytochemical research has identified 20 compounds in this species, including a diverse array of phytochemical classes (see the Complete Chemical Inventory below for the full list).
The identified compounds include the following categories:
- Flavonoid: antioxidant compounds that protect cells from oxidative damage
- Sterol: cholesterol-like compounds with anti-inflammatory properties
- Alkaloid: nitrogenous compounds with diverse pharmacological activities