Poison hemlock

Poison hemlock

The Enemy: Poison hemlock (Conium maculatum)

Strategy: This biennial plant grows up to 12 feet tall. This is the most toxic of all the plants that we have growing in the area. All parts of this plant are poisonous to livestock and humans, in fact, the extract of this plant was used to execute Socrates of ancient Greece. People have died from the plant when they have mistaken it for wild parsley and placed it into their salad. The plant hosts white flowers (don’t mistake this plant for water hemlock, wild parsley or wild carrot). This plant is easy to distinguish as the stems have a purple striping up and down them that the other plants do not. The leaves are fern-like and pinnately divided. The thick white taproot, which, when sliced into, resembles walls with hollow chambers.

Attack: This plant inhabits the riparian areas along streams and ditches or even where there are sub-waters near roadways. As the plant matures, it blocks out sunlight and robs the soil of valuable nutrients and water. Wildlife cannot travel through the bamboo like stems (although they don’t turn woody) and obviously few animals if any can feed on it to help control it.

Defense: There is one biological control insect — a moth that defoliates the plant. Mechanically digging up the plants can be effective in the first few years of establishment, just don’t lick your fingers after the tugging contest. Cover your hands with a latex or nitrile glove, then apply your leather gloves and get to removing. In pastures and rangeland, herbicides such as Escort XP, or Telar XP are best. On outer banks of a ditch, use Opensight. Treatments in early spring are best, but these products can be used right up to a late bloom stage of the plant.

To learn more, call Bonneville County Weed Superintendent Jeffrey Pettingill at 208-529-1397 or email weeds@co.bonneville.id.us.

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