Plants of the Eloise Butler Wildflower Garden

Nodding Bur Marigold is a low erect annual plant (up to 3 feet high but usually much less) of wet places, branching occasionally, but usually only within the inflorescence. Stems can be glabrous or have short stiff hairs. The central stem is angled (grooved).

Leaves are long and lance shaped with pointed tips, hairless, opposite, stalkless, with coarse teeth. The leaves clasp the stem, and as they are opposite, often appear to surround the stem.

Flowers occur in loose stalked clusters branching from the upper leaf axils near the top of the stem. The flower head is 1/2 to 1 1/2 inches wide and nods after or during flowering. The stalked head has two types of flowers. The outer circumference consists of about 8 yellow ray florets with rays of variable length. These are neuter or sometimes have styles, but are sterile. Rays have a point or notch at the tips. Some heads may lack ray florets entirely. The ray florets surround 40 to 100+ central disc florets with tubular orange-yellow corollas that have a five-lobed throat. Each disc floret has 5 stamens with darker anthers that tightly surround a single style. These are bisexual and fertile. The outside of the flower head has two sets of floral bracts, an inner layer of phyllaries, 6 to 8+, that are a pale yellow color and thin as to be somewhat translucent. The outer bracts (calyculi) are dark green, 5 to 8+ in number, and as long or longer than the yellow rays. These spread and curl backward as the flower head matures.

The seeds (cypselae) are blackish-brown, somewhat flattened to angled, and have 2 to 4+ barbed awns which stick to clothing and animal fur - hence the word 'bur' in the common names. Thoreau refers to the Bidens seeds as “shaped somewhat like a little flattish brown quiver, with from two to six downwardly barbed arrows projecting from it.” See his comments below.

Habitat: Nodding Bur Marigold grows from a shallow root system in wet but not flooded mediums. Being an annual, if sufficient seed sets, a sustaining colony is formed, unless subsequent flooding occurs. Depending on the amount of sun and the growing conditions and location, there will be variability in the plants, particularly in the flower. The seeds can tolerate some standing water early in the growing season, but the area must be free of standing water by mid summer for the seeds to sprout, which if they do, even late in the season, flowers will be produced as the plant is a fast grower.

Names: The genus name, Bidens, refers to the 2 "teeth" or the bristles on the cypsela, of the original type species for which the genus was named. It is from the Latin bis meaning 'two' and dens, meaning 'tooth, i.e. two-toothed. The species name, cernua is also Latin for 'nodding' or 'drooping'. The author name for the plant classification - 'L.' is for Carl Linnaeus (1707-1778), Swedish botanist and the developer of the binomial nomenclature of modern taxonomy.