Andromeda is a monotypic genus of flowering plants in the heath family Ericaceae, order Ericales, containing a single species: Andromeda polifolia, commonly known as bog-rosemary. The genus was established by Carl Linnaeus.
Andromeda polifolia is a small evergreen shrub, typically growing 10–20 cm (4–8 in) tall, rarely reaching 40 cm. Its slender stems bear alternately arranged, lanceolate leaves 1–5 cm long and 2–8 mm broad. The leaves are dark green on the upper surface (becoming purplish in winter) and white on the underside, with margins distinctly curled under — a feature that helps reduce water loss in exposed bog environments. Flowers are bell-shaped, white to pink, and 5–8 mm long, appearing in late spring to early summer. The fruit is a small capsule containing numerous seeds.
Two varieties are recognised, sometimes treated as separate species: A. polifolia var. polifolia, distributed across Northern Europe, Asia, and northwestern North America; and A. polifolia var. latifolia (synonym A. glaucophylla), found in northeastern North America.
The genus is restricted to bogs and other cold, peat-accumulating wetlands across the Northern Hemisphere. As a member of Ericaceae, it is strongly calcifuge — requiring acidic, low-pH growing conditions — and is typically associated with Sphagnum moss bog communities.
Etymology
The genus Andromeda was named by Carl Linnaeus following his 1732 expedition to Lapland, where he observed the plant growing in bogs and likened its isolated, delicate appearance to Andromeda of Greek mythology — a princess chained to a rock. The species epithet polifolia traces through Johann Christian Buxbaum to Johann Bauhin’s earlier use of Polifolia to denote plants with leaves resembling polium (possibly Teucrium montanum). The common name “bog-rosemary” reflects the superficial leaf resemblance to true rosemary, though the two plants are not closely related.
Distribution
Andromeda polifolia is native to cold, northern regions of the Northern Hemisphere, occurring across Northern Europe, Asia, and North America. Within its range it is restricted to bogs and other peat-accumulating wetland habitats; it is not found in drier or base-rich soils. The North American populations are split between a northwestern variety (var. polifolia) and a northeastern variety (var. latifolia, also known as A. glaucophylla).
Ecology
Andromeda is a specialist of Sphagnum-dominated bogs and cold peat-accumulating areas, where low nutrient availability, high acidity, and waterlogged soils exclude most competitors. As a member of Ericaceae, it is a calcifuge (acid-lover) and cannot tolerate alkaline or neutral soils. Its leaf margins curl under, reducing exposure of the white, reflective undersides — an adaptation that limits water loss in exposed, wind-swept bog conditions.
Cultivation
Andromeda polifolia and its cultivars require consistently damp, acidic soil (low pH) and perform best in partial shade — conditions that mimic their native bog habitat. They cannot tolerate alkaline soils or drought. Several cultivars have been selected for garden use; ‘Compacta’ and ‘Macrophylla’ have received the Royal Horticultural Society’s Award of Garden Merit. Plants are typically grown alongside other acid-loving ericaceous plants such as heathers and rhododendrons.
