Anchorage Daily News

The threat of invasive plants has received much public attention recently, and this article is the first of an occasional series on plants that now may pose a threat to the local environment.

SPLIT-LIP HEMPNETTLE

Brittlestem hempnettle, Latin name:Galeopsis bifida

The offender: This broad-leafed flowering annual is banned as a noxious weed in Alaska. It flourishes in such disturbed areas as roadsides, gardens, construction sites, erosion, farm land and open woods. This alien invader resembles a round-shaped shrub with spiky hairs along the square-sided stem. Leaves are oval to lance-shaped, and flowers -- white, pink or purple -- cluster atop the stem. The fused petals, with an upper and lower lip, inspired its name.

The split-lip hempnettle monopolizes soil moisture and nutrients, which keep other plants from thriving. Each plant can release 2,800 seeds, which can remain dormant for up to five years, though most germination occurs within two years. Fortunately, the seeds are too large to easily disperse like dandelion seeds on the wind.

Germination requires the warmer temperatures of late spring and early summer and ½ to 1 1/2 inches of soil. The plants grow to 3 feet and can reach a density of 400 per square acre. They can't sprout if other vegetation already exists.

Nipping in the bud: First and foremost, stop the seeds. Yank this plant out of the ground NOW. If it's a large infestation, the seed bank has probably already started. To stifle future seed growth, remove and replace the topsoil. Also, corn gluten might deter seeds from sprouting.

More flower for your bower: Find an early, fast-germinating plant or grass to compete with the hempnettle seeds. In native ecosystems, such as a forest understory, encourage the spread of ferns, grasses and other ground covers.

In the garden or yard, stick with easily adaptable plants such as grass, herbs, veggies, flowers or shrubs. Also, avoid bare soil for the invasive seeds to grow and plant other self-seeders and spreaders such as violas, strawberries, field mint, American dragonhead and hairy hedgenettle.

Early detection and control is cheaper than the expensive herbicide route.

Trash and burn: Split lip hempnettle has a minimal root system and can be easily pulled by hand. But use thick gloves to avoid those prickly nettles. And practice the EDRR method -- early detection/rapid response -- in early to midsummer before the flowers turn to seed. This process could take a few seasons, so don't be discouraged.

Once they're removed from the ground, stomp the plants flat, let them dry and then burn or bag them for the trash or landfill. Avoid the compost heap.

BIG WILD WORRIES: The Integrated Pest Management program at the University of Alaska Fairbanks Cooperative Extension Service offers more information about split-lip hempnettle and other invasives. Call the Anchorage office at 786-6300 or log on at

www.uaf.edu/ces/ipm/gabi.html

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