This biennial (or perhaps short-lived monocarpic perennial) is widely naturalized in temperate regions of North America; the carrot is a cultivar (ssp. sativus) selected from the wild type. D. carota is often abundant, especially on moderately dry but somewhat fertile soils of occasionally mowed roadsides, old fields and pastures. It has been present in Ky. since the mid-1800s or earlier (Rafinesque 1840; Gm). Rafinesque (1936, 1:31, 4:24-28) expressed uncertainty about its naturalized versus native status in North America, and described several segregates. D. pusillus Michx. is a native weedy annual that is widely known across southern states, north to Mo., Tenn. (Ch), Va. and perhaps Pa. (D. scariosus Raf.). Varied diagnostic characters, inconsistent in some cases, have been used for pusillus (Sm, F, Cr, Y, W). It is generally less robust, with smaller primary umbels (ca. 2-6 cm across versus 6-10 cm) that remain more or less flat-topped in fruit (versus with incurving rays); 2n = 22 versus 18. D. carota is now one of the most common hosts for Black Swallowtails, along with other alien Apiaceae. But before settlement, that butterfly must have been concentrated on native species like Cicuta, Cryptotaenia, Osmorhiza, Thaspium and Zizia. These plants have somewhat similar chemistry, including polyacetylenes (especially falcarindiol) and, in some cases but not Daucus, furanocoumarins (e.g.. Berenbaum 1981). Although varied pheniolics and carotenes (unsaturated hydrocarbons) in carrots are considered nutritious for humans, high falcarindiol content makes a bitter taste, especially in leaves and seeds. Leaves also contain pyrrolidine, an alkaloidal amine (part of nicotine) that is unusual as a pure compound within plants (Marion 1950). Although leaves and seeds have been used for culinary purposes in the past, leaves are bitter and may even cause skin irritations.