- Latin synonym: Heracleum laciniatum
- Name also: Golpar
- Family: Carrot Family – Apiaceae (Umbelliferae)
- Growing form: Perennial herb.
- Height: 150–200 cm (60–80 in.). Many-stemmed, bristly haired, from base red-brown, up to 50 mm (2 in.) thick, hollow, joints with septa. Smells of aniseed.
- Flower: Corolla regular, (outer corollas slightly zygomorphic and bigger), white, 15–30 mm (0.6–1.2 in.) wide; petals 5, deeply notched. Sepals stunted. Stamens 5. Pistil of 2 fused carpels, styles 2. Inflorescence a compound umbel, secondary umbels (20–)50–85. The bracts of primary umbels fall off early, the 10–18 bracteoles of secondary umbels do not fall off.
- Leaves: Alternate, stalked, base pod-like. Blade longer than wide, lower side densely haired, glabrous on top, pinnate, leaflets 5–7. Leaflets big, shortly and broadly lobed, with blunt-toothed margins.
- Fruit: Broadly obovate, 7–8 mm (0.28–0.31 in.) long 2-parted, slightly ridged schizocarp, oilducts only slightly club-shaped.
- Habitat: Surroundings of dwellings. Also ornamental plant.
- Flowering time: July–September.
- Harmfulness: Extremely harmful invasive species.
Persian hogweed is certainly not of Finnish origin, but that is close to all we know about its origin. The species probably originates from the Middle East, somewhere south of Caucasia, but has spread as an ornamental plant up to Northern Europe. The bristles contain poisonous substances which in combination with sunlight cause a severe, slowly healing eczema. When the fluid of the plant touches the skin, it has to be washed off immediately with water and soap. After the exposure one should avoid the sun for at least a week. For children the plant can even be dangerous, since they often play with the large leaves or use them as a hiding place.
Persian hogweed spreads diligently to the moist and nutritious areas surrounding the spot where it is cultivated. Is has become a real plague especially in northern Norway. Internationally the species is known widely as Tromso Palm, since in the town of Tromso it can nowadays be found in almost every garden. As a good competitor, the species can make up continuous Persian hogweed jungles suffocating all other plants. The seeds contain substances which stunt the growth of other plants and can even kill the plants growing close to it. In Finland Persian hogweed is being actively fought to prevent it from becoming a plague.
It is not easy to differentiate hogweeds from each other – there are actually several different species called Persian hogweed. The other large hogweed common in Finland, giant hogweed (H. mantegazzianum) is even bigger than Persian hogweed, single-stemmed and blossoms only once at the most. Good indicators for recognizing the species are the colour of the stem’s base and the hairiness of the leaves, but the best is probably the shape of the leaflets’ lobes.