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Phaseolus acutifolius
Fabaceae FAMILY

Phaseolus acutifolius

Phaseolus acutifolius

Edibility
3/5
Medicinal
2/5

Safety & Hazards

The seed contains various antinutritional factors, such as trypsin inhibitors, flatulent oligosaccharides and phytic acid[1]. The lectin activity is exceptionally high, but is readily reduced by cooking; whereas cyanogenic glucosides have not been detected[1]. Consumption of raw tepary bean flour has been recorded to cause death in mice and rats within 3 - 4 days, but soaking and cooking the seeds eliminated toxicity completely[1].

Cultivation Details

HabitAnnual Climber
Growth—

Phaseolus acutifolius is a plant mainly of the drier subtropics, though it can also be cultivated in warmer regions of the temperate zone so long as there is a sufficiently long growing season to ripen the crops in autumn. It can also be grown in tropical areas at elevations up to 1,900 metres so long as the climate is not excessively wet[2]. It prefers a mean annual temperature within the range 20 - 30°c, but can tolerate 8 - 38°c[2] It cannot be grown in areas where night temperatures fall below 8°c[2]. It prefers a mean annual rainfall of 600 - 1,000mm, tolerating 300 - 1,700mm[2]. Excessive rainfall may create vegetative growth at the expense of seed yield[2]. The plant can withstand heat and a dry atmosphere, though only very few varieties are suited for the wet tropics[2]. Requires a sunny position[2]. Succeeds in most soils that are well-drained[2]. Succeeds in poor, shallow soils[3]. Established plants are rather drought resistant[4].Prefers a pH in the range 6 - 7, but tolerates 5 - 8[2]. The crop can be grown on residual soil moisture[2]. Often cultivated for its edible seed, there are many cultivated forms with seeds considerably larger than the wild forms[5] The seedpods of wild forms have pods that burst open explosively when ripe to expel the seeds, which are smaller than cultivated forms[6]. The seedpods of cultivated forms remain closed when the seeds first ripen, making harvesting much simpler[6]. The species is highly daylength sensitive, growmg under natural field conditions during the long days of summer and beginning to bloom in late summer when daylength has fallen to around 13 hours[5]. Flowering occurs within 27 - 40 days from germination[1]. First harvest may be taken in as little as 60 days in the tropics, though in cooler climates it can be up to 120 days from sowing[2]. The seeds of many domesticated types of tepary bean are shattered less easily than those of wild types[1]. Average yields of dry seed under dry conditions are reported to be 450 - 800 kg/ha and with irrigation 0.9-1.7 t/ha[2]. In areas of poor rainfall, tepary bean has possibilities as a catch-crop where a rapid food supply is needed[3]. This species has a symbiotic relationship with certain soil bacteria; these bacteria form nodules on the roots and fix atmospheric nitrogen. Some of this nitrogen is utilized by the growing plant but some can also be used by other plants growing nearby[7].

Propagation

The seed of cultivated forms absorbs water easily; in moist soils the testa wrinkles within 5 minutes, whilst when soaked in water the testa wrinkles in 3 minutes[1]. This leads to quick and even germination[1]. The rate of germination increases with increasing temperatures from 10 - 35°c[1]. Seedling emergence is faster in white-seeded than in dark-seeded types[1]. The seed of wild forms usually has a hard seedcoat and will benefit from scarification before sowing in order to speed up and improve germination. This can usually be done by pouring a small amount of nearly boiling water on the seeds (being careful not to cook them!) and then soaking them for 12 - 24 hours in warm water. By this time they should have imbibed moisture and swollen - if they have not, then carefully make a nick in the seedcoat (being careful not to damage the embryo) and soak for a further 12 hours before sowing. The seeds of domesticated types have no dormancy, which is a disadvantage in humid regions, where fallen seeds will germinate rapidly[1]. Cite as: Temperate Plants Database, Ken Fern. temperate.theferns.info. 2026-02-21. <temperate.theferns.info/plant/Phaseolus+acutifolius>

Pollinators

Insects, Self

References

  1. [1]Protabase - Plant Resources of Tropical Africa. — http://www.prota.org ↩︎An excellent on-line database with detailed information on over 3,200 species of useful plants of Africa.
  2. [2]Ecocrop — http://ecocrop.fao.org/ecocrop/srv/en/home ↩︎Basic information on a wide range of useful plants, plus details of environmental needs where available.
  3. [3]Plant Resources of Southeast Asia — http://proseanet.org/ ↩︎Lots of information on the uses of the plants of SE Asia.
  4. [4]Mansfeld's Database of Agricultural and Horticultural Plants — http://mansfeld.ipk-gatersleben.de/pls/htmldb_pgrc/f?p=185:3:4292127278597336 ↩︎Terse details of a huge range of useful plants.
  5. [5]Taxonomy, Distribution, and Ecology of the Genus Phaseolus (Leguminosae-Papilionoideae) in North America, Mexico and — Freytag G.F. & Debouck D.G. · Botanical Researeh Institute of Texas · 2002 · http://www.brit.org/sida · ISBN 1-889878-11-1 ↩︎An excellent, detailed study of the genus Phaseolus, it has been made available on-line as an open access document.
  6. [6]Flora of SW Arizona — University of Arizona Herbarium · https://cals.arizona.edu/herbarium/content/flora-sw-arizona ↩︎An excellent flora, published on-line in PDF format
  7. [7]Nodulation Plants in GRIN Taxonomy — United States Department of Agriculture · http://www.ars-grin.gov/~sbmljw/cgi-bin/taxnodul.pl?language=en ↩︎An online database listing plants that have either positive or negative reports on root and stem nodulation with nitrogen-fixing bacteria.
  8. [8]Grassland Species - Profiles — http://www.fao.org/ag/AGP/AGPC/doc/Gbase/Default.htm ↩︎Terse information on over 650 species of plants that grow in grassland, including trees, shrubs and perennial plants as well as grasses. Gives a brief description of the plant, its range and habitat and some of its uses.
  9. [9]Native American Ethnobotany — Moerman. D. · Timber Press. Oregon. · 1998 · ISBN 0-88192-453-9 ↩︎Very comprehensive but terse guide to the native uses of plants. Excellent bibliography, fully referenced to each plant, giving a pathway to further information. Not for the casual reader.