- Name also: Bee-nettle, Edmonton Hempnettle (Canada)
- Family: Mint Family – Lamiaceae (Labiatae)
- Growing form: Annual herb.
- Height: 20–80 cm (8–32 in.). Stem branching, with swollen joints, 4-edged, often with purple base, joints and edges, rough-haired mainly along edges, lacking glandular hairs.
- Flower: Corolla irregular (zygomorphic), pale yellow, occasionally white or reddish, 20–35 mm (0.8–1.4 in.) long, fused, bilabiate, long-tubed, hairy. Upper lip convex; lower lip 3-lobed, central lobe purple, base with 2 glands. Calyx campanulate (bell-shaped), 5-lobed, lobes rigid, sharp-pointed. Stamens 4, of which 2 short and 2 long. Gynoecium composed of 2 fused carpels. Inflorescence lower part with long gaps, upper part denser, spike-like group formed of dense axillary whorls terminating stems and branches
- Leaves: Opposite, stalked. Blade ovate, sharp-tipped, feather-veined, smoothly haired, margin with large, sharp teeth. Inflorescence’s subtending bracts like stem leaves.
- Fruit: 4-parted schizocarp. Carpels elliptic, flat, almost glossy, brown.
- Habitat: Arable land, waste ground, gardens, soil heaps, forest margins, roadsides.
- Flowering time: July–September.
Large-flowered hemp-nettle is surely the most handsome of the hemp-nettles that grow in Finland. As well as the modest white, yellow and purple shades of the north, its flowers also include exotic pale yellow and dark violet. Its Finnish name refers to the straw-like form of its long calyx-tube, and it can only be pollinated by long-tongued bumblebees and honeybees which can reach down to the bottom of the flower and drink the abundant nectar. In the old days every child also knew large-flowered hemp-nettle as it was common practice to break off the corolla and suck out a drop of sweet nectar.
Large-flowered hemp-nettle has, like many of its relatives, spread to Finland from elsewhere in Europe. It gets along well with people and has never really settled in to the wild. It favours nutritious, preferably nitrogenous habitats where exuberantly growing plants can produce hundreds of seeds. Like its relatives, large-flowered hemp-nettle is able to throw its seeds a short distance as the calyx dries and suddenly collapses, throwing the seeds out. The spiny calyx is a much more efficient way to spread as it attaches to people’s clothes and animal fur. The spines also protect the plant from being eaten – as well as from eager weeders.