- Family: Borage Family – Boraginaceae
- Growing form: Annual herb. Main root straight, short.
- Height: 20–70 cm (8–28 in.) long. Stem limp, branched, bristly, barbed hairs along edges.
- Flower: Regular (actinomorphic), 2–3 mm (0.08–0.12 in.) wide. Corolla dark purple, fused, funnel-shaped, 5-lobed. Corolla mouth with white scales, 10 protuberances lower down. Calyx fused, irregular (zygomorphic), 5-lobed, hairy; enlarging after flowering to become stiff, flat, comprised of 2 multi-lobed parts, lobe tips spreading, barbed. Stamens 5. Gynoecium fused, single-styled. Flowers in axils, solitary or in pairs.
- Leaves: Alternate, partly virtually opposite (decussate). Lower leaves stalked, upper leaves stalkless. Blade narrowly elliptic, quite blunt.
- Fruit: 4-parted schizocarp. Mericarps elliptic, flat, grey-brown, densely granular, approx. 3.5 mm (0.14 in.) long.
- Habitat: Gardens, wasteland, potato fields, compost heaps, cowshed walls, seaweed piles.
- Flowering time: May–August.
- Endangerment: Near threatened.
Madwort is the only species in its genus, and with its limp stem, usually paired axillary flowers and enlarging calyx after flowering it differs in many respects from more typical borage family plants. It is possible that the young shoot can be mistaken for a forget-me-not.
Madwort favours nitrogenous places and is usually found in areas of human activity: it thrives especially well behind outdoor toilets, by cowshed walls, and in potato fields and rubbish and compost heaps. On the other hand madwort can also be found in gardens, ruins and places that seaweed naturally accumulates along shorelines. Just like many other plants that demand a cultural environment, madwort has become rarer as farmyards have become tidier and horse manure is no longer used so much.
Madwort can be found sporadically across the whole country, but its prevalence is clearly twofold: it grows on the one hand in the South-western Finnish archipelago, and on the other hand in Lapland. Madwort has probably grown in the south as long as the area has been cultivated, while in the north it is assumed to have arrived later, mixed in with Russian grain. Madwort spreads well: due to its hooked tips the calyx, which resembles a miniscule maple leaf and envelopes the ripening mericarps, is very adhesive. When the stem dries it breaks easily, so segments with mericarps can easily attach in their entirety to passing animals or people. Considering how easily madwort spreads, it is even more difficult to understand why it does not grow across the whole country. Different explanations have been offered, but none are very convincing.