Hemp-nettle

Hemp-nettle

The Enemy: Hemp-nettle (Galeopsis tetrahit)

Strategy: This weed can be found in the Pacific Northwest. It is in the mint family of plants and is an ever-increasing invasive weed in Canada and listed as a noxious weed in Alaska. It is a short growing plant that can commonly invade disturbed sites in upper highlands and forested areas. The plant usually grows to a height of 2 feet. It has square stems and the upper stems are covered with short hairs (very similar to stinging nettle but without the sting). The plant has a similar leaf structure to marijuana, thus the name hemp, that is serrated leaf margins and teardrop in shape. The inflorescence (flower) forms a terminal spike and is composed of whorls of pinkish flowers with dark markings on the lower lip. It produces a nutlet fruit, which turns into five-pronged burs, thus spreading throughout an area.

Attack: This plant is commonly found in disturbed (logged) forested sites. It has an aggressive taproot which allows it to steal nutrients and moisture from desirable habitat. It especially spreads in areas of skid trails, which, in our area, can be transferred to ATV and horseback riding trails.

Defense: Don’t let this plant hitch-hike on livestock or hiking nor riding gear. If you do find it on the aforementioned sites, throw the seeds into the fire or place them in the center of the trail, thus if they germinate they will be tromped or controlled by mechanical means. If possible, disking or plowing in the spring can be utilized. Products such as 2,4-D in early spring and Banvel, Starane and Vista should be used when the plants become larger. In range sites use Opensight. Definitely terminate the plant before it goes to seed.

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