- Name also: Marsh Rosemary, Bog-rosemary, Marsh Andromeda
- Family: Heather Family – Ericaceae
- Growing form: Perennial dwarf shrub. Rhizome long, creeping.
- Height: 10–30 cm (4–12 in.). Stem ascending, sparsely branched, woody.
- Flower: Corolla urceolate (pitcher-shaped), pink, 5–8 mm (0.2–0.32 in.) long, fused, shallowly 5-lobed. Sepals 5. Stamens 10. A single carpel. Inflorescence a 4–5-flowered umbel terminating shoots, flowers long-stalked, nodding.
- Leaves: Alternate, short-stalked, erect, overwintering. Blade narrowly elliptic–linear, taper-tipped, leathery, glabrous, dark green on top, underside greyish white, with entire, revolute margins.
- Fruit: Spherical, 4 mm (0.16 in.) long, with 5 compartments, erect capsule.
- Habitat: Bogs, swamps, fens, peat-covered areas beside ponds.
- Flowering time: June.
Bog rosemary is not particularly highly esteemed in Finland, as folk names like ‘bog heather’ show. The father of botany Carl von Linné on the other hand adored the species, as is evident from the way that its scientific name compares it to the princess Andromeda from Greek mythology, who was renowned for her beauty and who was chained to a shore-side rock as a sacrifice for the sea monster. Perseus, the hero of the tale, flew on his winged horse Pegasus so save the damsel in distress, but bog rosemary is still chained to the peat.
Bog rosemary is very widespread in boggy habitats and thrives in both wet swamps and dry bog moss hummocks. The plant’s annual growth is lime green or with slightly reddish shades and is covered with a greyish, wax-like film. Strangely bloated and beautiful wine-red shoots can quite often be found in the bogs – in this case the plant has been destroyed by a fungus. Black patches on the leaves on the other hand are a sign that the plant is being attacked by another kind of fungus. Plant-eaters do not bother with bog rosemary as it contains andromedotoxin which is very poisonous, although there is no record of anyone dying from eating the plant.
Bog rosemary’s flower buds develop already in the previous growing season. The reddish flower is beautiful, and as it contains nectar and is fragrant it is clearly intended to attract pollinators. These do not however fly around bogs much at the beginning of summer when the plant is flowering, so for safety’s sake it is self-pollinating. Especially on the northern bogs and fell areas the seeds do not develop at all, but the species is not dependent on its seeds to propagate itself. It spreads efficiently through its underground rootstock and runners.