Accession Count: 1
Common Name:
blackthorn
Family Name:
Fabaceae
Botanical Name:
Senegalia mellifera
Sub Species:
Variety:
Forma:
Cultivar:
Characteristics:
Blackthorn is a woody perennial, usually single trunked tree with spherical crown growing up to 8 m (26 ft) (1, 3, 5). It can, however, grow as a multi-trunked specimen with a more “inverted cone” (obconical) shaped canopy (1). Bark is light to dark grey at maturity, initially smooth but developing longitudinal fissures and a more purplish-black color with age (1). Branches develop close to the ground, young branches are olive brown with clear lenticels and 2-6mm (<1 inch) claw-like, paired, black colored, and downward curving thorns below each node, while older branches become brown to grey and only occasionally maintain the curved spines (1). Young leaves, which are bright green becoming dull, grey-green with time, are bipinnately compound with a hairy or glabrous, 0.2-0.4 cm (<1/10 inch) rachis and 1.2 cm (1/2 inch) petiole (1). Unlike most Senegallia species, this one has up to 3 pairs of pinnae with relatively large 15 x 12mm, blue-green leaflets showing marginal hairs (1). are present. (Subsp. mellifera usually has 2 pinna pairs and hairless leaflets, whereas subsp. detinens has 3 pinna pairs and leaflets with a fringe of marginal hairs (5). A gland is usually present on the upper surface of the petiole and at the base of the upper pinnae pairs. After the initial 3-year juvenile period, flowers will appear twice a year prior to the rainy seasons (3). Flower buds appear on 1 year old wood, may have a slight purple or pink tinge, while the bisexual flowers are small, globe-shaped, fragrant, cream or pale pink colored from the exserted filaments, and packed tightly on very short, indeterminate spikes (1, 3). (Flowers on subsp. mellifera are more closely packed along branchlets and have more elongated spikes whereas subsp. detinens have flowers in globe-shaped short spikes (5). Fruit pods are red-brown when young and mature white to tan, tapered slightly both ends, 9 cm wide and 2.5 cm wide (3.5 inches long and 1 inch wide) and contain 2-3 seeds (1)
Compound:
sen mel
Geographic Origin:
Africa
Ecozone Origin:
Biome Origin:
Natural History:
Blackthorn trees grow in a wide range of countries from Northeast Africa (Egypt to Tanzania) and east to Arabia as well as in Southern Africa (Namibia and Botswana) (3). A plant of the semi-arid grasslands of tropical and subtropical Africa, it is found at elevations from sea level to 1,500 meters (0 – 5000 feet elev) (3, 4) They survive in the semi-desert and are common in dry woodland and semi-desert areas where they can spread by coppice growth and from seeds to form impenetrable tangled, spiny 100 m dia. thickets that threaten diversity and must be managed by fire control (1, 3, 4). The specific epithet "mellifera" is of Latin origin, meaning "honey-bearing" and refers to the fragrant flowers of the species (2,3,5). The previously accepted subspecies name "detiens" comes from the Latin word detino, meaning "to hold back", and refers to the unwelcoming nature of the vicious thorns (3).
Cultivation Notes:
Blackthorn is noted as being tolerant to temperatures as low as 2C (35F) (once mature) and at the other extreme to temperatures higher than 40C (104F) (2). It is widely adapted to a variety of soil types from sandy, clayey and loamy (3,4). It is even known to grow on brackish soils in Botswana (3). The species is extremely drought-resistant once established, growing generally in areas with 400-800 mm (15-30 inches) of annual rainfall but also growing in areas with 100 mm (~1 inch) of annual rainfall (3,4). Blackthorn can be vegetatively propagated or sown. Seed is ready for collection before the rainy season (5). Orthodox seed can be stored for several years in hermetic storage at 10°c with 4.5-9% humidity (3). When ready to grow from seed, pre-soak overnight in hot water that is allowed to cool (3,5). The seedlings grow quite slowly and are not likely to be more 200 mm (8inches) high by the end of the first season (5). Thereafter, growth will be about 0.5m (1.5 feet) per year (1). 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 (3). In its natural setting, it is noted as having a relatively short lifespan of 10 years (4).
The blackthorn tree is not highly cultivated in the United States but has great potential due to its drought resistance and attractive cream flowers.
Ethnobotany:
This tree is valuable for both shade and fodder. The leaves and stems have a high percentage of protein. The leaves and pods are a very nutritious fodder consumed by livestock and wild animals and nectar attracts bats, bush babies, and bees. The flower nectar produces a high quality honey, hence the name mellifera. The wood makes a very hard slightly elastic timber, that does not split easily, and is very durable, and well suited for construction and fencing as it is both termite and borer-proof (1, 3, 4). The heartwood is a very dark brown, almost black when oiled or polished, with clear delineation with the more yellow-white sapwood (3, 4). Since the wood is usually only available in fairly small sizes (branches are usually small in diameter), it is often used for small construction projects, or for making small items like tool handles (1, 3). Wood is often used for fuel and in the manufacture of charcoal manufacture (1, 3). Twigs are chewed and used to clean teeth (1, 3). Bast fibers from the wood are used for wicker (3).
Gum collected from injured stems is edible, commonly used in chewing gum and confectioneries as an alternative to the gum more commonly obtained from A. senegallia (1, 3). When added to clay, the gum forms a hard substance that can be used as a flooring material (3). Resin from the trunk is also used an emulsifier, stabilizer and a means of preserving flavor and retarding the crystallization of sugar (3).
The leaves contains a small amount of N-dimethyltryptamine (DMT), a hallucinogenic drug causing an effect that may persist for days or weeks after ingestion (1). The bark and roots are used in ethnomedicine to make a decoction used in treating stomach problems, sterility, pneumonia, malaria and syphilis (3, 4). The bark also contains astringent tannins, which are administered orally to treat diarrhea and dysentery, and internal bleeding (3, 4). External application of the plant tannins is used as a treatment of wounds and other skin problems, haemorrhoids, foot and mouth odor, as well as some eye problems (3).
Height:
20 - 50 feet
Width:
16 - 20 feet
Growth Rate:
Slow Growing
Grow Season:
Spring
Flower Season:
Spring
Color:
Cream
Function:
Accent
Spread:
Spreading
Allergen:
Invasive:
Benign
Toxicity:
Benign
Hardy:
Hardy
Water Use:
Low water Use
Citations:
See also:- Ross, J.H. (1979) A Conspectus of the African Acacia Species. Botanical Research Institute.
- Timberlake, Jonathan. (1980). Handbook of Botswana acacias. Ministry of Agriculture.
- Timberlake, Fagg, Barnes. (1999). Field Guide to the Acacias of Zimbabwe. CBC Publishing
- https://treesa.org/senegalia-mellifera-2/
- http://pza.sanbi.org/senegalia-mellifera-subsp-detinens
- https://arboretum.arizona.edu/research/desert-legume-tree-rescue
- https://www.cabi.org/isc/datasheet/2328
