Phaseolus affinis Piper
Phaseolus atropurpureus DC.
Phaseolus canescens M.Martens & Galeotti
Phaseolus dysophyllus Benth.
Phaseolus schiedeanus Schltdl.
Phaseolus semierectus atropurpureus (Moc. & Sessé ex DC.) M.Gómez
Phaseolus vestitus Hook.
Macroptilium atropurpureum is an annual to perennial, deep-rooting legume. The twining stems can be 5 metres or more long and up to 5mm in diameter; they scramble over the ground and grow into other plants for support. Stems close to the ground may develop secondary roots, usually on light soils when the soil surface remains continuously moist for some weeks[
The plant is used to reclaim and stabilize soils.
S. America - northern Brazil, Peru, Ecuador, Colombia, French Guiana; C. America - Panama to Mexico; Caribbean
Moist or dry thickets, usually twining over shrubs, sometimes procumbent on banks, at elevations up to 1,200 metres in Guatemala[
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The plant grows well from the subtropics with fairly cold winters to the seasonal tropics, succeeding in semi-arid areas but not doing so well in humid areas; it can be found at elevations up to 2,900 metres. It grows best in areas where annual daytime temperatures are within the range 21 - 32°c, but can tolerate 13 - 36°c[
]. When dormant, the root system can survive temperatures down to about -8°c, but young growth can be severely damaged at -1°c[
]. It prefers a mean annual rainfall in the range 650 - 1,800mm, but tolerates 200 - 2,800mm[
Requires a sunny position for best growth, tolerating light shade[
]. Tolerant of a range of well-drained soils, other than heavy clays,and growing well in soils of moderate fertility and tolerating poor fertility[
]. Succeeds in dry soils and very tolerant of drought once established[
]. Prefers a pH in the range 6 - 7.5, tolerating 4.5 - 8.5[
Plants grow vigorously from seed - in weeded beds they can flower and produce seed in their first year, but when grown amongst other plants they usually take longer[
The plant generally lives from 1 - 10 years[
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[
The plant is used for the revegetation and stabilization of earthworks, and in road and railway cuttings and embankments[
]. It could be useful as a cover crop or as a fallow crop in shifting cultivation[
Seed - it has a somewhat hard seedcoat and may 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. Seed is generally sown in situ.
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