Amoreuxia is an American genus of 4 species in family Bixaceae. It was previously placed in family Cochlospermaceae, now united with Bixaceae. Amoreuxia species have long, carrot-like roots that produce annual growth during the summer rainy season. They are reported to be edible for people and herbivores. Their relative, the tropical American tree Bixa ornellana, yields seeds that are ground into the spice annato.
Leaves are palmate, green to bluish-green, and may be slightly glaucous. Flowers are borne in arched cymes of several, opening one per day. They are in various apricot shades, large for a small plant, often with darker blotches at the bases of petals. Fruits are fairly large, elongated and tomentose. The species are very similar and difficult to distinguish without all plant parts available.
Seeds have a papery brown seed enclosure and a hard, shiny, black outer coat. Seed shape can help distinguish species.
To sprout, soak seeds in water for a few hours to loosen the enclosure and remove it. Lightly scarify the seed until the inner white endosperm can be seen. Soak in water just until they swell (no longer than overnight) and sow in fast-draining soil in a deep container. They are susceptible to damping off in some climates. Plants grow rapidly and bloom in their second season. In fall tops die down completely. New growth is very late to resume the following late spring or early summer.
Amoreuxia gonzalezii (Sprague & Riley) occurs from a few populations in extreme southern Arizona, USA south into Sonora, México, and just into Sinaloa, México. Plants grow to 40 cm tall in rocky limestone or granitic soils in full sun. Flowers are up to 2.5" / 6.4 cm across. It is threatened by herbivory, habitat destruction by ranching and invasive grass species degrading habitat. The species has been proposed for listing and protection under the US Endangered Species Act but so far has not been listed. It seeds are globose. To the naked eye, they greatly resemble seeds of okra (Abelmoschus esculentus, family Malvaceae.) Flowers open after dark and close about 7:30 the following morning.
The first photo shows one plant in its container, with a lens cap for scale. None of the flowers is fully open in rainy weather. The second is a close-up of the inflorescence. The third shows the plant from above. The fourth shows an open flower, which is 1.5"/3.75 cm across. Many small beetles were enjoying the flower but flew off when the camera approached. Photos are copyright 2013, Leo Martin.
Resources
United States Forest Service
https://www.fs.usda.gov/wildflowers/Rare_Plants/profiles/Critically_Imperiled/amoreuxia_gonzalezii/index.shtml
Southwest Environmental Information Network
http://swbiodiversity.org/seinet/taxa/index.php?taxon=2422
Amoreuxia malvifolia (A. Gray) is reported from the states of Chihuaua and Durango in México.
Resources
Missouri Botanical Garden Tropicos
http://legacy.tropicos.org/Name/50123643
LISTADOS FLORISTICOS DE MEXICO - IX. FLORA DE DURANGO, UNAM
http://www.ibiologia.unam.mx/BIBLIO68/fulltext/lfl9.html
Amoreuxia palmatifida (Moc. & Sessé ex DC.) is more widespread in southern Arizona, USA, growing into Sonora and Baja California Sur, México. It is very similar to A. gonzalezii but it seeds are reniform (kidney-shaped.) Leaf differences are subtle but visible when plants of the two species are grown side-by-side. It would be difficult to identify single plants without seeds. The first photo shows three plants in a 5-gallon nursery container, which is 10.5"/27 cm across and 11"/28 cm deep. The second photo is a side view. Photos are copyright 2013, Leo Martin.
Resources
United States Department of Agriculture
http://plants.usda.gov/core/profile?symbol=AMPA3
Southwest Environmental Information Network
http://swbiodiversity.org/seinet/taxa/index.php?taxon=2423
Amoreuxia wrightii (A. Gray) is native from southern Texas, USA, through México, Venezuela and Perú.
Resources
United States Department of Agriculture
http://plants.usda.gov/core/profile?symbol=AMWR2
Pictorial Flora of Purola Preserve, N. Hays County, Texas, Bob Harms, University of Texas
http://w3.biosci.utexas.edu/prc/HaysFlora/pages/AMWR2.html
Lady Bird Johnson Wildflower Center, University of Texas
http://www.wildflower.org/plants/result.php?id_plant=AMWR2