Amaranth family (Amaranthaceae)
Description: This native plant is a summer annual about ½–2½' tall and ½–3' across. Large specimens branch frequently and have a bushy appearance; they are broader toward the bottom than the top. Small specimens are more sparsely branched and have a scraggly appearance. The stems are whitish green to white and round or slightly furrowed. The alternate leaves are up to 1" long and ¼" across; rarely are they larger than this. Both the stems and the leaves are hairless, or nearly so. The side branches often develop at right angles (90°) from the central stem. Each leaf is light green, oblanceolate, and smooth or slightly undulate along the margins. Sometimes the leaves have yellowish or reddish tints.
From the axil of each leaf, there develops a small cluster of inconspicuous flowers. Each flower is surrounded by 3 lanceolate bracts about 1/8" in length; each bract has an elongated tip that is stiff. Because White Amaranth is monoecious, there are pistillate (female) and staminate (male) flowers. Regardless of its gender, each flower has 3 green sepals that are lanceolate and no petals. Each pistillate flower has an ovary with 3 styles, while each staminate flower has 3 stamens. The blooming period occurs from mid-summer to early fall and lasts about 2 months. The flowers are wind-pollinated. Each pistillate flower develops a single seed that is surrounded by a wrinkled membrane (utricle). This membrane splits open around the middle to release the seed. Each small round seed is dark reddish brown to black, shiny, and somewhat flattened. The root system consists of a taproot. During the winter, this plant can break off at the base and roll around in the wind, thereby distributing the seeds. Occasionally, it forms colonies.
Cultivation: Typical growing conditions are full sun, mesic to dry locations, and a barren soil containing sand, gravel, or clay.
Range & Habitat: White Amaranth occurs in most areas of Illinois and is occasional to locally common; it is less common in southern Illinois. Habitats include dry gravel prairies, sand prairies, cropland, abandoned fields, vacant lots, and barren areas along railroads and roads. Generally, this plant prefers dry barren areas with scant vegetation. In Illinois, it is primarily a railroad weed.
Faunal Associations: The wind-pollinated flowers don't attract many insects. Various insects feed on the foliage of Amaranthus spp. (Amaranths), including Disonycha triangularis (Flea Beetle sp.), the caterpillars of the skipper Pholisora catullus (Common Sootywing), and the caterpillars of several moths. The seeds of Amaranths in upland areas are eaten by the Mourning Dove and various granivorous songbirds (see Bird Table) that hunt for food near the ground in open areas, particularly during the fall and winter.
Photographic Location: A vacant lot near a railroad in Urbana, Illinois.
Comments: Another common name for White Amaranth is Tumble Pigweed, or just Tumbleweed. In the Great Plains, this weed is often blown against fences, where it piles up; this is less common in Illinois. White Amaranth can be distinguished from Amaranth spp. (Amaranths) by its white stems and small light green leaves; the foliage has a pale appearance overall. Furthermore, the side stems often develop from the slender central stem at right angles (90°), providing this plant with a rather awkward and angular appearance. Other Amaranths have larger darker leaves and they usually produce terminal spikes of flowers. An exception is Amaranthus blitoides (Prostrate Pigweed), which produces inconspicuous axillary flowers like White Amaranth. However, Prostrate Pigweed has darker leaves and a prostrate or sprawling habit. Two other species that occur along railroads, Kochia scoparia (Kochia) and Salsola tragus (Russian Thistle), are also tumbleweeds with a similar appearance. They tend to be somewhat larger in size than White Amaranth (although not always) and their leaves are linear to lanceolate. Unlike White Amaranth, Russian Thistle is rather prickly, while Kochia has long white hairs near the flowers. They are all members of the Amaranth family.