Bidens tripartita Trifid Bur-marigold

Trifid Bur-narigold is a species of lake margins, canal banks and marshes. The sharply-toothed leaves are arranged in opposite pairs on the stem and are variously lobed, some unlobed and some with partial lobes. It can be confused with Beggarticks (Bidens frondosa) which has more distinctly lobed leaves. The 2 species also differ in the arrangement of the barbs on the edges of the fruits (achenes) and this is probably the best way to distinguish them unambiguously (see diagram). In Trifid Bur-marigold the barbs point backwards and with Beggarticks they point forwards. It is rather local in West Glamorgan and it may have decreased here in the last 50 years. A reasonable population is present in brackish marsh on Baglan Dunes.

Native