Today's “Plant of the Day” is Conyza canadensis (L.) Cronq from the Asteraceae family (subfamily Asteroidiae). In English, this plant is known as “Horseweed”, “Butterweed” or “Colstail” and in German as “Kanadisches Berufskraut”.
C. canadensis - habitus
It's an upright growing herb, which can reach heights between 20 and 150 centimetres (or between 0.7 to 4.9 feet). The robust, edged stalk is rich of branches and leaves. Both, shoots and leaves, are covered by many rough hairs. The foliage leaves are narrow-lanceolate and bright green.
C. canadensis - leaves
Like all Asteraceae, the inflorescences of C. canadensis consists of many small heads, which consists of many small flowers by themselves. As a member of the Asteroidiae subfamily, this species has radial, tubular flowers in the centre of the head and cygomorphical ray flowers in the periphery. The tubular flowers are yellow, the ray flowers white; the latter are very small and short. All heads are combined to a larges, terminal paniclse again. So, each panicle can consist of until 100 heads.
C. canadensis -inflorescences
This species is native to the USA and the Southern regions of Canada, but is also a neophyte in Europe and all over the world. It's very undemanding towards its places to grow or its soils. You can find it at ruderal wastelands, roadsides, gardens and building sites. After World War II, it was one of the first plants, that grew in the ruins of the bombed German cities. This year (2011) seems to be a good year for this plant, because I've found many exemplars in cities like Düsseldorf or Solingen.
C. canadensis - stalk