Willow leaf acacia
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Willow leaf acacia ( Acacia saligna ) - habitus |
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| ( Labill. ) HLWendl. |
The Acacia saligna ( Acacia saligna ) is a plant from the genus of Acacia ( Acacia ). It is native to southwestern Australia , but has spread widely as a neophyte in South Africa and causes great damage there. Lately attempts have been made to use the species as an energy crop .
description
The willow leaf acacia is a bushy shrub or tree that reaches heights of between two and six meters. The branches are often drooping, curved, hairless and, in young plants, covered with a whitish dust. The rind is gray and contains around 30.3% tannins .
In the alternate, sometimes somewhat fleshy leaves , the petiole is broadened and takes on the function of the leaf blade, so-called phyllodes . The phyllodes are drooping and variable in shape and size. The shape is linear to lanceolate, curved or straight and between seven and 25 centimeters long and four to 20 millimeters wide. The leaves grow larger towards the ground. They are entire, glabrous and green to gray-green, "frosted", with a protruding middle nerve. At the base of each phyllodium there is a one to two millimeter wide gland that secretes sugary nectar .
The axillary, stalked inflorescences are five to twenty-member grapes , which in their youth of overlapping bracts are enveloped. Each flower head, up to about 10 millimeters in size, bears 25 to 55 golden yellow, mostly hermaphrodite or rarely male flowers . The individual, seated flowers are five-fold with a double flower envelope with long stamens and the individual flower heads sit on stems up to 20 mm long. The bald ovary is on top with a long, thready stylus .
After flowering, linear, flattened pods form that are eight to twelve centimeters long and four to six millimeters wide. They are constricted between the individual, up to ten seeds. The flattened seeds are dark brown to black and shiny. They are elongated, elliptical to ovate and five to six millimeters long. The seeds have a small, yellowish aril as an appendage.
distribution
Willow leaf acacias do not place high demands on their location, but seem to avoid high altitudes. A deep, sandy soil in moist areas, such as on rivers or streams, lake shores or in swamp areas, but also at the base of granite deposits or in dunes on the coast is preferred. The soil can be acidic or alkaline. The species has a moderate salt tolerance .
The natural range is in southwest Australia , there it extends from the Murchison River in the north southeast to the area of Esperance on the south coast. However, it is absent in the far south in the region around Albany .
Neophytic occurrences
The willow leaf acacia was brought in by people in South Africa in 1840 . Plantings were intended to stabilize the sand dunes in the Cape Flats around Cape Town . Today the species is considered the most dangerous invasive plant in the Western Cape .
Gackeltrappen consume the seeds of the willow-leaf acacia and thus contribute significantly to their spread.
In the meantime, a rust fungus species Uromycladium tepperianum and weevils of the genus Melanterius have also been introduced in order to master the steadily growing population of the willow-leaf acacia.
Systematics
The French botanist Jacques Julien Houtou de Labillardière described the plant in 1806 under the name Mimosa saligna . The German botanist Heinrich Ludolph Wendland referred to this Basionym, but classified the species under the name Acacia saligna in the genus of acacia ; its first description was published in 1820.
Further synonyms for the species are Acacia cyanophylla Lindl. and Racosperma salignum (Labill.) Pedley .
ecology
The willow leaf acacia lives symbiotically with nodule bacteria (Rhizobiaceae) and can thus bind nitrogen from the air. It can conquer new habitats very quickly, as the young plants grow extremely quickly.
The seeds are spread by ants who carry them into their nests and eat the seed stalk (aril). There the seeds can survive for a very long time until the soil is disturbed and the seeds germinate. This way the species can survive forest fires well.
The phyllodes of the plants are, for example, eaten by the caterpillars of the line swarm ( Hyles livornica ).
Use
The fast-growing species is often planted to stabilize the soil or to create windbreak hedges. It is also popular to cultivate in gardens because of the yellow flowers.
The wood of the willow leaf acacia is traditionally used as firewood and to produce charcoal. Since 2000 attempts have been made to use the fast-growing plant to produce biodiesel ; for this purpose, cultures were planted in the Mediterranean area and harvesting machines were developed. The rapid growth - between 1.5 and 10 cubic meters of biomass arise per year and hectare - predestines the species for this purpose. However, the wood is light and very damp, which makes processing difficult.
The phyllodes of the willow-leaf acacia are very popular with sheep.
Individual evidence
- ↑ Acacia saligna GBIF.org (1st March 2019) GBIF Occurrence Download doi : 10.15468 / dl.vqssco
- ^ M. Correia, S. Castro, V. Ferrero et al .: Reproductive biology and success of invasive Australian acacias in Portugal. In: Botanical Journal of the Linnean Society. Volume 174, Issue 4, 2014, pp. 574-588, doi : 10.1111 / boj.12155 .
- ↑ RS Knight, IAW Macdonald: Acacias and korhaans: An artificially assembled seed dispersal system. In: South African Journal of Botany / Suid-Afrikaanse Tydskrif vir Plantkunde. 57 (4), 1991, 220-225.
- ↑ Comm. Acac. aphyll. 26. 1820; see entry at GRIN Taxonomy for Plants .
literature
- Robert Powell: Leaf and Branch: Trees and Tall Shrubs of Perth . Department of Conservation and Land Management , Perth 1990, ISBN 0-7309-3916-2 .
- AR Wood: Beating the Australian: The Acacia Gall Rust Fungus is Winning the Battle against Port Jackson . In: Veld & Flora . tape 93 , no. 2 , 2007, p. 104-105 .
Web links
- Acacia saligna at Useful Tropical Plants.
- Acacia saligna from Weeds of Australia, accessed March 7, 2019.
- Entry in the Flora of Pakistan (English)
- Entry in the Handbook of Energy Crops (English)