Where it's from

Southern Scandinavia

What Pale swallow-wort does to the habitat

Swallow-wort drives away grassland birds. It forms a dense carpet and climbs over adjacent plants and prevents the regeneration of trees. It threatens lichens, mosses and plants growing in shallow soil. Butterfly larvae that feed on it have a higher mortality rate.

It is sometimes called “dog strangling vine” because a dog charging head long into it will get tangled up. The scary thing is that it emits 2400 seeds per square meter. And many of those seeds are polyembryonic, that is, each seed can produce many more seeds.

Management

You need to dig up the crown of each plant as that is where the stems sprout from. Be sure to do your work before seed dispersal.

Mowing and cutting do help manages it, but may not prevent resprouting, which means more cutting and mowing. If you use the herbicide triclopyr be very careful because it will also kill nearby vegetation.

Since it is hard to eradicate, early detection and action are key to management.

DESCRIPTION

Botanical Glossary

Cynanchum rossicum is an herbaceous, perennial vine that is vegetatively very similar to Cynanchum louiseae. The stems can reach 1.5 m (5 ft.) in length. The leaves are opposite, and ovate and acute in shape. They are 9-12 cm (3.5-4.7 in.) long, and 5-6 cm (2-2.5 in.) wide. The petioles measure 1 cm (0.4 in.) in length. Flowers are borne in opposite, axillary cymes from June to September. The corolla of Cynanchum rossicum is 5-obed, glabrous and ranges in color from maroon to dark pink; its lobes are longer than wide and are shaped like an isosceles triangle. The membrane connecting the segments of the corona is approximately 1/2 the height of the corona. The peduncles are 2-5 cm long. The fruits are slender follicles measuring 4-6 cm long and 0.5 cm wide. Page References Fernald 1176, Gleason & Cronquist 399, Holmgren 374.