Amaranthus and Chenopodium
(Pig Weed and Lambsquarters)
By: H. Wayne Shew, Ph.D.
NAB Certified Pollen Counter
Pig weed and goosefoot (also called lambsquarters) are late summer and early fall flowering plants that belong to the family Amaranthaceae. These plants often become significant weeds in some locations and have even become invasive species in some places. They also serve as a food source and cause allergic rhinitis in some individuals.
The pollen produced by the plants in these genera acts as an allergen for many people, leading to bouts of hay fever. Even though the flowers are small they are produced in large numbers, and thus the total pollen production from these plants can be abundant. Species of both Amaranthus and Chenopodium produce pollen grains that look like one another; pollen grains that cannot be readily distinguished using a light microscope. No attempt is made to distinguish between the pollen produced by plants of these two genera and thus the pollen counts are reported as Chenopod/Amaranth to the National Allergy Bureau. The pollen grains are spheroidal and pantoporate. That is, the pollen grains have 20-65 pores per grain and the pores are typically distributed globally. The pollen grains range in size from 14-50 microns in diameter. The pollen grains resemble a golf ball because of the many pores present in the exine which resemble the dimples on a golf ball.
Amaranthaceae is a family of angiosperms that contains approximately 175 genera and more than 2,500 species. Most members of this family are herbs or subshrubs and the family has a worldwide distribution. The family contains both annuals and perennials and one unique adaptation of the family is the ability of many species to grow in saline soils. A number of species are important as food crops and ornamentals.
The leaves of members of this family are simple and usually have an alternate arrangement. They are sometimes succulent and many species have a reddish color due to the presence of betalain pigments which are present in vacuoles in the plant cells. These betalain pigments are yellow and red indole pigments that replace the anthocyanins that are the typical red pigments present in plant leaves. The betalain pigments are found in the leaves, flowers, fruits, and roots of various members of this plant family and in other plants in the order Caryophyllales to which the Amaranthaceae family belongs.
The flowers are small and can be bisexual or unisexual. The flowers are frequently borne in dense spikes (a type of inflorescence) and each flower will often have several (three) bracts present below them. Fruit types vary in this family but most members produce utricles, (small bladderlike one-seeded indehiscent fruits, that resemble achenes), with occasional species producing capsules or berries.
One interesting fact about this family is that it has the largest collection of plants that have a C4 photosynthetic pathway for carbon fixation. C4 plants use a different method of carbon fixation compared to that of most plants, which are described as C3 plants. C3 plants use the Calvin cycle as the method of carbon fixation.
A number of species in this family are important food crops, and some are cultivated as garden ornamentals. One important food crop species is Beta vulgaris, beets. Varieties of beets include garden beets, sugar beets, and chard. Other species serving as food sources include lamb’s quarters (Chenopodium album), quinoa (C. quinoa), spinach (Spinacia oleracea), Inca wheat or love-lies-bleeding (Amaranthus caudatus), and red amaranth (A. cruentus).
There are numerous species of Amaranthus planted as garden ornamentals; for example, Joseph’s coat (A. tricolor), prince’s feather (A. hybridus), and love-lies-bleeding (A. caudatus). These species and varieties are used as garden ornamentals because of their colorful foliage and flowers.
Amaranthus was used as a food crop by the Aztecs and is still a native, cultivated crop in Peru. Today, Amaranthus is grown throughout the world for its production of grain-like fruits. The fruits are not true grains like wheat, rice, barley, or oats, but because they have a similar nutritional profile to the grains they are described as pseudo-cereals. Amaranthus fruits can be ground and used as a flour in cooking, as a thickener in recipes, or eaten as a snack. Amaranthus foliage is also edible, highly nutritious, and is described as resembling the taste of spinach. Amaranthus is eaten as greens and grain throughout the world: Africa, China, India, Nepal, Pakistan, and South America.
Chenopodium was also used as a food source in ancient civilizations and has made a comeback in modern culture as a gluten free food source, with quinoa often touted as a health food. In addition to eating the seeds, an oil of Chenopodium can be extracted from the seeds and used like other vegetable oils. Tender shoots and leaves of species of goosefoot can be used as a food source by boiling or steaming them.
Recipes for amaranth and goosefoot dishes
References for Chenopodium: