Cow Parsnip vs. Giant Hogweed (and other Apiaceae Plants)

Giant Hogweed always causes a stir, and rightfully so! Exposure to the plant’s sap can cause redness and inflammation, severe skin burns, eye damage, and phototoxic (light‑sensitivity) reactions for years after contact. Luckily for those in Parkland County, according to Alberta Agriculture and Forestry, all plants reported as giant hogweed in Alberta have been proven to be cow parsnip. 

Cow parsnip, giant hogweed, spotted water hemlock and poison hemlock share a family — the carrot family, Apiaceae — and grow in similar conditions. It is important for those with livestock, children or pets to identify which they might see on their land, as some plants can cause harm.

Clothes, skin and PPE should be washed after contacting any of these plants. If you have symptoms, it is recommended to seek medical attention for proper treatment. If you notice Giant Hogweed, please report it to Parkland County’s Agricultural Department by calling 780‑968-8467.

1. Giant Hogweed (Heracleum mantegazzianum)
   
   • A prohibited noxious weed in Alberta
   • Grows 3 – 6 metres tall
   • Stem is 3 – 10 cm in diameter
   • Umbel flowers are up to 1 metre across, and umbrella shaped
   • Toothed, alternate leaves, deeply lobed leaves that look like a hand with fingers, spanning 150 cm or more. 
   • Underside covered in coarse white hairs
   • Stem has many purple spots and stiff bristly hair
   
   
2. Cow Parsnip (Heracleum maximum)
   
   Even though they are cousins, cow parsnip is not as nasty, but care should still be taken when handling them as their sap can cause rashes, blistering and sensitivity. 
   
   • Grows 1 – 2.5 metres tall
   • Stem is 2.5 – 5 cm in diameter, has few purple areas, deep ridges and fuzzy hairs
   • Umbel flowers are up to 30 cm across and flat-topped
   • Palmate- shaped, compound leaves, similar to a maple leaf — divides into three segments, 
   covered in soft hairs
   • Native and common in Parkland County — pollinators love it!
   
   
3. Spotted Water Hemlock (Cicuta maculata)
   
   • Native to Parkland County
   • Grows 100 cm high
   • Stem is round or slightly angular with purplish lengthwise streaks
   • Leaves are twice compound with many leaflets and sharply toothed edges (margins). Vein goes to notches between the teeth on margins
   • Umbel flowers, grows 12 cm in diameter. White flowers with four to six petals
   • Extremely poisonous to people and livestock
   
   
4. Poison Hemlock (Conium maculatum)
   
   • Herbaceous perennial plant
   • Grows between 5 – 10 feet
   • Stems are hairless, hollow, smooth and purple splotched, smells unpleasant when broken
   • Leaves are alternate, divided into three to four leaflets, oblong and lacy with a triangular shape. They are also hairless
   • Tiny, white flowers in loose clusters in compound umbels
   • All parts are extremely poisonous to people and livestock, dried stems are toxic for 3 years