Classification of the genus Acacia (in the wider sense) has been subject to considerable debate. It is generally agreed that there are valid reasons for breaking it up into several distinct genera, but there has been disagreement over the way this should be done. As of 2017, it is widely (but not completely) accepted that the section that includes the majority of the Australian species should retain the name Acacia, whilst other sections of the genus should be transferred to other genera. This species is transferred to Vachellia[
Acacia canescens (Britton ex Britton & Killip) García-Barriga & Forero-
Acacia flexuosa Humb. & Bonpl. ex Willd.
Acacia humboldtii Desv.
Acacia lutea (Mill.) Britton
Acacia macracantha Humb. & Bonpl. ex Willd.
Acacia macracanthoides Bertero ex DC.
Acacia microcephala Macfad.
Acacia obtusa Humb. & Bonpl. ex Willd.
Acacia pellacantha Meyen ex Vogel
Acacia pellacantha Vogel
Acacia platyacantha Schltdl.
Acacia punctata Humb. & Bonpl. ex Willd.
Acacia subinermis Bertero ex DC.
Mimosa atomaria Poir.
Mimosa flexuosa (Humb. & Bonpl. ex Willd.) Poir.
Mimosa lutea Mill.
Mimosa macracantha (Humb. & Bonpl. ex Willd.) Poir.
Poponax cansecens Britton ex Britton & Killip
Poponax cowellii Britton & Rose
Poponax flexuosa (Humb. & Bonpl. ex Willd.) Britton & Rose
Poponax lutea (Mill.) Britton & Rose
Poponax macracantha (Humb. & Bonpl. ex Willd.) Killip
Poponax macracanthoides (Bertero ex DC.) Britton & Rose
Vachellia lutea (Mill.) Speg.
Vachellia macracantha is a tree growing up to 10 metres tall.
The plant is sometimes cultivated for its tannins and for fuel[
Vachellia macracantha specimens are usually cyanogenic (capable of producing the toxin hydrogen cyanide). Eightynine percent of specimens from Mexico and Central America were found to be cyanogenic, whilst 91% of specimens examined from South America tested positive for cyanide, usually strongly so. The compound proacacipetalin is responsible for this activity
S. America - all countries except Uruguay and Brazil; C. America - Panama, Mexico; Caribbean - Trinidad to the Bahamas; N. America - Florida
Shrubby vegetation, successional fields, edge of roads, thorn-scrub forests, dry forests, savannahs, dry deciduous forests; at elevations from sea level to 1,700 metres.
A very variable species, leading to many synonyms being given to plants that were originally thought to be distinct.
Vachellia macracantha occasionally hybridizes in the wild with Vachellia cochliacantha and with Vachellia pennatula.
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 bark of all Acacia species contains greater or lesser quantities of tannins and are astringent. Astringents are often used medicinally - taken internally, for example. they are used in the treatment of diarrhoea and dysentery, and can also be helpful in cases of internal bleeding. Applied externally, often as a wash, they are used to treat wounds and other skin problems, haemorrhoids, perspiring feet, some eye problems, as a mouth wash etc[
Many Acacia trees also yield greater or lesser quantities of a gum from the trunk and stems. This is sometimes taken internally in the treatment of diarrhoea and haemorrhoids[
Vachellia macracantha is used as an auxiliary plant in timber plantations of tropical South America[
Tannins are obtained from the bark[
The wood is used for fuel[
The seed of most, if not all, members of this genus has a hard seedcoat and may benefit from scarification before sowing to speed up 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.
Acacia seeds that have matured fully on the bush and have been properly dried have a hard seed coat and can be stored in closed containers without deterioration for 5 - 10 years or more in dry conditions at ambient temperatures. It is best to remove the aril, which attracts weevils and can lead to moulds forming. The arils are easilyremoved by placing the seeds in water and rubbing them between the hands, then drying the seeds and winnowing them[
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