Growing form
Perennial herb. Rootstock creeping, with runners. Hemiparasite.
Height
15–25 cm. (6–10 in.) Stem rigid, unbranched, upper part bilaterally sparsely hairy, reddish brown.
Flower
Corolla irregular (nearly zygomorphic), yellowish white, 12–15 mm (0.48–0.6 in.) long, fused, bilabiate, long-tubed, rose-scented. Upper lip with flattened sides, tip bent sharply downwards; lower lip 3-lobed, sharply descending oblique, twisted to the side. Calyx bilabiate, 5-lobed, glabrous. Stamens 4. Gynoecium fused, single-styled. Inflorescence short, quite dense terminal spike.
Leaves
Alternate; no rosette. Leaf blade narrowly ovate–linear, quite glabrous, thick, pinnately lobed, lobes toothed.
Fruit
Egg-shaped, sharp-tipped, brown, approx. 14 mm (0.56 in.) long, oblique, capsule opens from one side.
Habitat
Fell heaths and mountain birch woodland, also beside streams and rivers in coniferous forests.
Flowering time
July–August.

Lousewort’s flower offers pollinators a hard nut to crack. The lower lip on the flower of Lapland lousewort is strongly twisted to the side in such a way that there is no easy landing site for insects. Only the most skilful insects get the nectar that is waiting at the bottom of the corolla tube. However, even on the Lappish fells, there are a whole swarm of bees who act as pollinators, attracted to Lapland lousewort by its rose-like scent. It is relatively rare in Lapland for plants to compete for pollinators using scent. Lapland lousewort’s seed production is however often weak, but the reason is not necessarily the efficiency of the pollinator, rather the crop is taxed by seed-eating caterpillars. So lousewort’s tightly closed flower has perhaps not been developed to make things difficult for insects but rather to prevent seed-destroyers getting in.

In years when there is a respite from pests, Lapland lousewort is also able to reproduce sexually. The seeds are intended to be food for mountain birds: e.g. Lapland and snow buntings spread the seeds efficiently over long journeys. Lapland lousewort is however always quite easy to find in northernmost Finland’s treeless mountain tops, in mountain birch woodland and even in the coniferous forest belt down to Pello and Rovaniemi. Although seed production might fail, the plant also spreads through its long-lived and strongly branched rootstock, and its numbers remain stable. Like other louseworts, Lapland lousewort is a hemiparasite which grows sucker roots onto the rootstock of a growing host plant. In Lapland lousewort’s case at least dwarf birch and wild bilberry act as host plants.

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