Galeopsis ladanum aka Hemp Nettle

Galeopsis ladanum is an annual in the mint family, Lamiaceae. The RHS calls it broad-leaved hemp nettle. Other names include holy hemp, red hemp nettle, and dog nettle. Plants For A Future gives Europe as its native range. Its listed distribution also reaches northern Turkey and the Caucasus. It is not native to Britain or Ireland. In Britain, it occurs as a rare introduction on cultivated ground.

This plant reaches about 2 feet [0.6 metres] in height. As an annual, it completes its life cycle within one year. Its flowers appear from July through October. Each flower has both male and female organs. Insects pollinate the flowers, and the plant is also self-fertile. The supplied sources give no detail on flower colour or shape. They also provide no clear account of its leaves or stems. There is no supported width estimate for garden plants.

Plants For A Future reports that it grows in most soils. It accepts sandy ground, loam, and heavy clay. It also tolerates mildly acid, neutral, and mildly alkaline soil. Choose a site with moist soil and avoid deep shade. It can grow in sun or light woodland shade. The evidence gives no cold-hardiness rating or winter temperature limit. Its broad soil tolerance does not establish how well it copes with drought.

The species is sometimes grown in wild gardens and cultivated beds. Sow its seed directly where it will grow in spring. Plants For A Future says germination usually takes about a month. Its long flowering season may suit a wild garden planting. The sources do not describe specific pests or diseases. Plants For A Future does not flag it as a weed risk. That assessment does not establish its behaviour in every region.

Treat this plant as poisonous, not as a food crop. Plants For A Future warns that poisoning can cause paralysis. It gives the species no food or medicinal rating. No medicinal uses are recorded in the supplied evidence. The seeds yield a drying oil used to polish leather. This practical use does not show that the oil is edible. The evidence offers no separate assessment of safety for pets.