The Dioecious Amaranthus spp.: Here to Stay

“Bid amaranthus all his beauty shed, And daffodils fill their cups with tears, To stew the laurate hearse where Lycid lies.” Paradise Lost, John Milton (1667) “Immortal amaranth, a flower which once In Paradise, fast by the Tree of Life, Began to bloom, but soon for Man's offence, To Heav'n remov'd, where first it grew, there grows, And flours aloft shading the Fount of Life.” Paradise Lost, John Milton (1667) “There are no fields of amaranth on this side of the grave” Imaginary Conversations “Aesop and Rhodope” in works of Walter Savage Landor (1846) “Weeds never die” Danish proverb There are nearly 75 species in the genus Amaranthus, part of the Amaranthaceae family, worldwide. In this large genus, there is a distinct group of 10 species that are dioecious (separate male and female plants). In contrast to the monoecious Amaranthus spp. which are represented by species endemic to every continent, the dioecious Amaranthus spp. are all native to North America. The Amaranthus spp. have a long documented history of being fellow travelers with humans. In recent years, three dioecious Amaranthus spp.: Palmer amaranth (Amaranthus palmeri S. Wats.), common waterhemp (Amaranthus rudis Sauer), and tall waterhemp Amaranthus tuberculatus (Moq) Sauer have become major weeds to row crops in North America. Palmer amaranth has become a very troublesome weed to cotton (Gossypium hirsutum L.), corn (Zea mays L.) and soybean Glycine max (L.) Merr. production in large parts of the southern United States, and the waterhemp complex is now a major weed pest in corn and soybean production in the midwestern United States (Horak and Loughin 2000; King 1966; Mabberly 1997; Robertson 1981; Sauer 1950, 1955, 1972; Wax 1995).