Mesquite

Prosopis juliflora (Sw.) DC.

Synonyms - Mimosa juliflora, Neltuma juliflora.

Family: Fabaceae (was Mimosaceae)

Names:

Prosopis is from the Greek pros meaning towards and Opis the goddess of agriculture and abundance and refers to the invasive nature of the plant.
Juliflora is from the Latin iulus meaning catkin and flora meaning flower and refers to the cylindrical or catkin-like flower head.
Mesquite is from the Mexican name for the plant.

Summary:

A variable legume ranging from a many stemmed low shrub through to a single trunk perennial tree to 15 metres high. It has long sharp straight spines, divided leaves and long curved pods coming from long cylindrical clusters of yellow cream flowers.

Description:

Cotyledons:

Two.

Leaves:

One or two pairs of opposite "branches" with 12-18 pairs of opposite leaflets, Usually deciduous but tend to be evergreen in WA.
Stipules - Paired, yellowish spines or none.
Blade - Of leaflet, dark to bright green, oblong, 5-12 mm long, 1.5-2.5 mm wide and rounded at the tip. Upper surface almost hairless to hairless . Lower surface with a few hairs on the midribs and edges to densely hairy.

Stems:

Straggly, crooked, arched branches. 1000-5000 mm tall. Straight, paired, stipular spines up to 100 mm long. Branchlets with scattered or downy hairs becoming hairless with age. Central wood of stem is reddish brown with yellow sapwood on the outside. Brown to black trunks. Woody.
Three forms -
a) Short many stemmed shrub, 1000-3000 mm high on dry sites.
b) Large single stemmed tree, 6000-15000 mm high with a trunk up to 1000 mm thick near permanent water.
c) Branches from the base forming dense thickets, 5000-8000 mm high on intermittently wet areas and flood plains. Bark thick with shallow fissures.

Flower head:

Groups of 2-5, spike like, cylindrical racemes. Each raceme 60-100 mm long and on a stalk. Arise from the axils near the ends of the branches.

Flowers:

Greenish yellow, small, fragrant. On short stalks.
Ovary -
Calyx - Bell shaped. 5 toothed.
Petals - Joined at the base or free
Stamens - 10, stick out of the flower.
Anthers - Tipped with a gland that falls off.

Fruit:

Straw coloured, fleshy pod, filled with sweet pulp, 120-200 mm long x 10 mm wide and constricted between the seeds when mature. 10-20 seeds that stay in the pod. The pods are flat when immature.

Seeds:

Brown to red brown, shiny, hard, flattened, oval to egg shaped, 2.5-7 mm long, 2-5 mm wide. Central ring on each side. Each seed in a box like flattened shell.

Roots:

Branched taproot, 15,000-20,000 mm deep. Mass of laterals near the surface.

Key Characters:

1 Leaflets 5-15 times as long as broad, 20 mm long, widely spaced along a single pair of leaf segments. Prosopis glandulosa var. glandulosa
1 Leaflets 2-5 times as long as broad, up to 15 mm long, not widely spaced along the leaf segments
2 Leaf segments 1, rarely 2, pair(s), leaflets 12-18 pairs, 5-12 mm long, flowering spike shorter than leaves
3 Stems and branches becoming glabrous with age, pods 150 mm long, 10 mm wide P. juliflora
3 Stems and branches generally pubescent, pods 120-150 mm long, 7-10 mm wide P. flexuosa
2 Leaf segments 2-3 (occasionally 5, rarely 1) pair(s), leaflets 10-30 pairs, 4-15 mm long, flowering spike longer than leaves
4 Leaf segments 2-3, rarely 1 pair(s), leaflets 12-30 pairs, 4-13 mm long, downy and leathery P. velutina
4 Leaf segments 2 pairs, leaflets 12-15 (18) pairs, 7-12 mm long, glabrous except long hairs along the margin, or shortly hairy on the upper surface P. juliflora x P. velutina
4 Leaf segments 2-5, rarely 1 pair(s), leaflets 10-15 pairs, 4-9 mm long, moderately pubescent P. pallida
Adapted from Parsons (1992) adapted from Pedley (1977).

Biology:

Life cycle:

Perennial. Seeds germinate in summer after rain in hot conditions. Top growth is slow as roots develop. A dormant bud zone extends for 150-200 mm below ground level. These buds shoot to form multi-stemmed plants if top growth or roots are disturbed. In WA growth slows in winter. In other states the plant loses its leaves in winter and growth resumes in spring. Plants flower when they are 2-3 years old and 1000-1500 mm tall. It flowers in summer and seed matures 35-40 days after flowering.

Physiology:

Optimum temperature for growth is 29-32oC.
Seedlings are tolerant of damage if cotyledons are left intact.
Very drought tolerant.

Reproduction:

Reproduces by seeds and suckers.

Flowering times:

Summer in western NSW.

Seed Biology and Germination:

Produces large quantities of pods and seed.
Burning encourages seed to germinate.
Passage through the gut enhances germination.
Optimal temperature for germination is 29oC.

Vegetative Propagules:

Suckers from crown and roots and rooting from branches covered with soil.

Hybrids:

There appears to be considerable intergrading between various Prosopis species in Australia.

Allelopathy:

Pods and leaves release toxins that reduce the growth of other plants.
Buffel grass release toxins which reduces the growth of Mesquite.

Population Dynamics and Dispersal:

The main spread was by deliberate introductions, movement in flood water and passing in dung. Local spread is by suckering and branches taking root where they are covered by soil.

Origin and History:

Central and North America and the north end of South America.
Introduced as an ornamental garden plant, shade and shelter plants and for stabilising mine sites in the early 1930's.

Distribution:

NSW, NT, QLD, SA, VIC, WA.

Courtesy Australia's Virtual Herbarium.

Habitats:

Drainage areas, settlements and mine dumps.

Climate:

Semi-arid, sub-tropics and tropics.

Soil:

Heavy soils, sands, sandy loams and red earths.

Plant Associations:

Open Mulga. Bimble Box woodlands.

Significance:

120,000 ha infested in WA.

Beneficial:

Ornamental.
Honey plant.
Used to stabilise mine dumps.
Timber used for posts, handicrafts and fuel.
Pods are a nutritious feed, seed needs to be crushed for better digestion.

Detrimental:

Aggressively invades pastoral land, excluding other species and forming dense thickets, which interfere with mustering and restrict access to water.
Dense stands eliminate grass cover, which results in greater erosion.
Thorns injure hooves and puncture tyres.
Weed of gardens, mine dumps, range lands, drainage lines, roadsides, old settlements and disturbed areas.

Toxicity:

Pods and seed may be toxic when fed with other feeds.
Stock may be poisoned if they consume the pods over extended periods.
Long stringy edges of pods form hard string balls in the stomach of cattle.

Legislation:

Noxious weed of NSW, NT, QLD, SA, VIC and WA.

Management and Control:

Graze the area but prevent stock from spreading seeds in dung to clean areas. Hold stock for 14 days in seed free areas to allow them to pass seed before moving them to clean areas.
Single plants should be removed with roots to 250 mm deep to prevent suckering. Mechanical removal is likely to be most effective in spring when root reserves are low. Chaining, root raking and then ripping the remaining stumps provides reasonable control. Clopyralid, glyphosate, picloram and triclopyr provide good control when applied between December and October, one to two weeks after 25 mm or more rain or as soon as flowering commences. Hexazinone and tebuthiuron also provide good control.
Buffel grass allelopathy helps control seedlings.
Maintenance of perennial grasses will reduce reinfestation.

Thresholds:

Eradication strategies:

Prevent seed set.
Control established plants mechanically or with herbicides.
Plant Buffel Grass and other perennial grasses.
Chaining twice, dozing remainders, root raking and herbicide treatment of regrowth and seedlings has provided good control in WA.
Clopyralid applied in autumn with a carpet roller has given good control in the USA.

Herbicide resistance:

Biological Control:

A beetle, bug and looper are being investigated for biological control.

Related plants:

See Key characters above to distinguish Prosopis species.
Algaroba (Prosopis pallida or Prosopis limensis) occurs in WA.
Honey Mesquite (Prosopis glandulosa var. glandulosa or Prosopis juliflora var. glandulosa) has hairless leaves and pods and much narrower leaflets whose length is 5-15 times their width. The pods are less constricted between the seeds.
Quilpie Mesquite (Prosopis flexuosa)
Velvet Mesquite (Prosopis velutina or Prosopis juliflora var. velutina) has downy leaves and pods and is a garden escape.
Prosopis juliflora x Prosopis velutina.

Plants of similar appearance:

African Boxthorn (Lycium ferocissimum)
Black Locust (Pseudoacacia spp.) has paired stipular spines.
Common Sensitive plant (Mimosa pudica) occurs in the NT.
Giant Sensitive tree (Mimosa pigra) occurs in NT, QLD and NSW.
Mimosa bush (Vachellia farnesiana was Acacia farnesiana) has unbranched, paired stipular thorns.
Parkinsonia (Parkinsonia aculeata) has up to 100 pairs of leaflets that usually fall off leaving the main axis and it has a very sharp spine where the leaf joins the branch.

References:

Auld, B.A. and Medd R.W. (1992). Weeds. An illustrated botanical guide to the weeds of Australia. (Inkata Press, Melbourne). P172. Diagram. Photo.

Cunningham, G.M., Mulham, W.E., Milthorpe, P.L. and Leigh, J.H. (1992). Plants of Western New South Wales. (Inkata Press, Melbourne). P376.

Hussey, B.M.J., Keighery, G.J., Cousens, R.D., Dodd, J. and Lloyd, S.G. (1997). Western Weeds. A guide to the weeds of Western Australia. (Plant Protection Society of Western Australia, Perth, Western Australia). P181-182. Photo.

Lamp, C. and Collet, F. (1990). A Field Guide to Weeds in Australia. (Inkata Press, Melbourne).

Lazarides, M. and Hince, B. (1993). CSIRO handbook of economic plants of Australia. (CSIRO, Melbourne). #1023.2.

Meadly, G.R.W. (1965). Weeds of Western Australia. (Department of Agriculture - Western Australia). P91-94.

Parsons, W.T. and Cuthbertson, E.G. (1992). Noxious weeds of Australia. (Inkata Press, Melbourne). P449-454. Photos.

Pedley L. (1977) Austrobaileya 1:25-42.

Acknowledgments:

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