Flora of North America species comparison

The green links below add additional plants to the comparison table. Blue links lead to other Web sites.
enable glossary links

Amaranthaceae

amaranth family
Habit Herbs, rarely subshrubs, annual or perennial; trichomes simple (branched in Tidestromia).
Stems

without nodal spines (Amaranthus spinosus sometimes with paired nodal spines).
Leaves

alternate or opposite, exstipulate, usually petiolate;

blade margins entire (entire or serrulate in Iresine; entire, crispate, or erose in Amaranthus).
Inflorescences

cymules arranged in spikes, panicles, thyrses, heads, glomerules, clusters, or racemes; each flower subtended by 1 bract and 2 bracteoles (latter sometimes 1 or absent in Amaranthus).
Flowers

bisexual or unisexual (plants then monoecious or dioecious), hypogynous, generally small or minute;

tepals mostly (1–)4–5 or absent, distinct or connate into cups or tubes, scarious, chartaceous, membranaceous, or indurate;

stamens 2–5, filaments basally connate into cups or tubes, rarely distinct, alternating with pseudostaminodes (appendages on staminal tubes) or not, anthers 2-locular with 1 line of dehiscence or 4-locular with 2 lines of dehiscence;

ovary superior, 1-locular;

ovules 1 or, rarely, 2–many;

style 1 or absent;

stigmas 1–3(–5).
Fruits

utricles, dry, dehiscent or not.
Seeds

black, reddish brown, or brown, lenticular, subglobose or globose (rarely cylindric), usually small;

embryo peripheral, surrounding mealy perisperm.

Amaranthaceae
Distribution
Nearly worldwide; most abundant in tropics; subtropics; and warm-temperate regions; evidently absent from alpine and arctic regions
[BONAP county map]
Discussion

Genera ca. 65, species ca. 900 (12 genera, 80 species in the flora).

Centers of diversity for Amaranthaceae are southwestern North America, Central America, South America, and Africa south of the Sahara Desert. Generic limits are not well defined in some groups; fewer than 60 or more than 70 genera could be recognized.

Some species occur in severe habitats such as sandy, calcareous, gypseous, saline, or serpentine soils in deserts, semideserts, and seashores. Some species are weedy, including the major agricultural weeds in Amaranthus. Some species are cultivated as ornamentals, particularly Amaranthus caudatus (love-lies-bleeding), A. hypochondriacus (prince’s-feather), A. tricolor (Joseph’s-coat), Celosia cristata (cockscomb), and Gomphrena globosa (globe-amaranth). Native Americans domesticated white-seeded grain amaranths (A. caudatus, A. cruentus, and A. hypochondriacus) for use as cereal grains. Some species of Amaranthus and Celosia are potherbs.

Amaranthaceae are usually divided into subfamilies Amaranthoideae (anthers 4-locular with two lines of dehiscence) and Gomphrenoideae Schinz (anthers 2-locular with one line of dehiscence). Amaranthaceae and Chenopodiaceae have long been recognized as allied families that share a number of features: generally small flowers, one perianth whorl, a syncarpous gynoecium with a superior ovary and often only one ovule, basal or free-central placentation, pollen characteristics, centrospermous embryo development, betalain pigments, and P-type form (c) sieve-element plastids.

(Discussion copyrighted by Flora of North America; reprinted with permission.)
Key
1. Distal leaves alternate
→ 2
1. Distal leaves opposite
→ 5
2. Flowers unisexual (plants monoecious or dioecious); utricles 1-seeded
→ 3
2. Flowers bisexual; utricles 2+-seeded
→ 4
3. Shrubs
Iresine
3. Herbs, annual, rarely perennial
Amaranthus
4. Leaf blades mostly lanceolate, ovate, or deltate; pseudostaminodes absent
Celosia
4. Leaf blades linear; pseudostaminodes alternating with filaments on staminal tubes
Hermbstaedtia
5. Flowers unisexual (plants dioecious); inflorescences terminal, diffuse, open panicles
Iresine
5. Flowers bisexual; inflorescences terminal and/or axillary glomerules, heads, or spikes
→ 6
6. Inflorescences sessile glomerules or condensed spikes, axillary
→ 7
6. Inflorescences pedunculate heads or spikes, terminal and sometimes axillary near stem tips
→ 10
7. Inflorescences several-flowered, axillary spikes; pseudostaminodes present
Alternanthera
7. Inflorescences 1-20-flowered, axillary glomerules; pseudostaminodes present or absent
→ 8
8. Indumentum of branched or barbed trichomes, densely covering plant (rarely glabrous); pseudostaminoides present
Tidestromia
8. Indumentum of simple trichomes; pseudostaminoides absent
→ 9
9. Tepals connate proximally, tips 1-veined; filament tubes inserted distally on perianth tubes; basal rosette leaves usually absent at anthesis
Guilleminea
9. Tepals distinct, 3-veined; filament tubes ± free from tepals; basal rosette leaves present at anthesis
Gossypianthus
10. Inflorescences simple or compound spikes
→ 11
10. Inflorescences globose or cylindric heads or spikes
→ 12
11. Inflorescences mostly compound, interrupted spikes; tepals connate into indurate tubes with lateral crests or spines, lanate
Froelichia
11. Inflorescences simple spikes or few-branched panicles, flowers progressively farther apart below; tepals basally connate into indurate tubes, without ornamentation, ± glabrous
Achyranthes
12. Inflorescences not immediately subtended by leaves
Alternanthera
12. Inflorescences immediately subtended by 2 or more leaves
→ 13
13. Leaves fleshy, sessile; blade linear to narrowly obovate, glabrous except in axils
Blutaparon
13. Leaves not fleshy, petiolate or sessile; blade ovate to obovate, pilose at least abaxially
Gomphrena
Source FNA vol. 4, p. 405. Authors: Kenneth R. Robertson, Steven E. Clemants.
Parent taxa
Subordinate taxa
Achyranthes, Alternanthera, Amaranthus, Blutaparon, Celosia, Froelichia, Gomphrena, Gossypianthus, Guilleminea, Hermbstaedtia, Iresine, Tidestromia
Name authority Jussieu
Web links 
Unless otherwise noted, all data comes from the online version of the Flora of North America, who have made most of their content available via a Creative Commons license (CC BY 4.0).



Type/paste one or more Latin names into the boxes above; matching taxa will show up below the box as you type. You can use the up/down arrow keys to move through the list.

(If the plant you're looking for doesn't show up in the auto-complete list, that means it either isn't described in Flora of North America yet, or it's listed under a synonym. And please note that Flora of North America is still missing several plant families, including Apiaceae, Boraginaceae, and Polemoniaceae.)

The species comparison tool is brought to you by:
Northwest Wildflowers