Description: This adventive plant is a summer annual about 1½–3' long; it branches occasionally, especially near the base. The stems are erect, ascending, or sprawling (often the latter); they are light green, more or less white-mealy, and terete or angular. The larger stems often have white longitudinal veins. The lowest leaves are opposite, while the remaining leaves are alternate; they have slender petioles up to 1" long. The leaf blades are up to 3½" long and ¾" across, becoming gradually smaller as they ascend the stems; they are green, flat, and either smooth or slightly undulate along their margins. The leaf blades have different shapes, but they are usually lanceolate-ovate, lanceolate, or oblong-linear; some leaves may have 1 or 2 lobes toward the base of their blades. The upper surface of each blade is hairless or glabrous, while the lower surface is often white-mealy.
The upper stems terminate in spikes or
spike-like panicles of flowers; axillary spikes also develop from some of the
upper leaves. The flowers are arranged in sessile clusters along the spikes or
the branches of the panicles. Common Orach is monoecious with separate male
(staminate) and female (pistillate) flowers on the same plant. Each male flower
has 5 sepals and 5 stamens; it is whitish green and about 1/8" (3 mm.) across.
Each female flower has an ovary with 2 styles and a pair of small bracts at its
base; it is green and about 1/8" (3 mm.) across. The male flowers lack petals,
while the female flowers have neither petals nor sepals. The flowers and
branches of each inflorescence are white-mealy. The blooming period occurs
during late summer into the fall. Pollination is by wind. The bracts of the
female flowers enlarge in size, becoming triangular-hastate in shape and about
1/5" (5 mm.) in length; they form a flattened fruit that encloses the
developing seed. Mature seeds are flattened, circular, and shiny black; each
seed is covered by a thin rough membrane that is difficult to remove. The root
system consists of a branching taproot. This plant spreads by reseeding
itself.
Cultivation: The preference
is full sun to light shade, moist to mesic conditions, and a fertile loamy
soil. Toleration of salty alkaline conditions is quite good, although in
Illinois this species is usually found in ordinary garden soil.
Range &
Habitat: Common Orach occurs occasionally in central and northern
Illinois, while in the southern part of the state it is uncommon (see
Distribution
Map). This species is native to Eurasia and northern Africa. Habitats
include woodland borders, gardens, edges of yards, unmowed areas around
telephone phones and tree stumps, areas along railroads and roadsides, dumps,
and waste areas. Areas with a history of disturbance are preferred. In
Illinois, this species is not invasive of natural habitats.
Faunal Associations: Very little is known about
floral-faunal relationships for herbaceous Atriplex spp. in the Eastern
United States. Because the foliage and seeds of Common Orach are similar to
those of many Chenopodium spp. (Goosefoots), it seems likely that the
floral-faunal relationships of the former are similar to floral-faunal
relationships of the latter. In particular, granivorous songbirds (e.g.,
various sparrows) probably eat the seeds. The caterpillars of Emmelina
monodactyla (Plume Moth sp.) feed on Common Orach.
Photographic Location: The upper photograph was
taken near a vegetable garden in Urbana, Illinois, while the lower 2
photographs were taken in Champaign County, Illinois, along the edge of a
wooded area.
Comments: This plant has unusual arrowhead-shaped fruits. While other Atriplex spp. have such fruits, there are usually more lobes and other irregularities along the margins of their fruits. The foliage of Common Orach is very similar to the foliage of some Chenopodium spp. (Goosefoots). However, the latter have button-shaped fruits with 5 folded sepals. Because of the variability of its leaves, different varieties of Common Orach have been described. The typical variety (described here) has lanceolate leaves, while var. littoralis has linear leaves and var. hastata has triangular-hastate leaves. Some authorities consider these varieties to be different species (see Mohlenbrock, 2001). Common Orach should not be confused with Atriplex hortensis (Garden Orach), which is occasionally grown in gardens as either a potherb or ornamental plant. This latter species has fruits with nearly orbicular bracts that are conspicuously veined. In dry areas of the Western states, there are woody to semi-woody Atriplex spp. that are quite distinct. These are referred to as 'Saltbushes.'