African mahogany (Khaya senegalensis)

Assessment ID: 1002
Jurisdiction: North Territory
Methodology: Northern Territory Weed Risk Management System - terrestrial
Management area: Darwin and Katherine Regions

Notes: 

Status: PUBLISHED
Last updated: 2/9/2026 4:07:35 pm AEST

Questions answered: 39 / 47

Weed Risk: 116.16 (Medium)
   Invasiveness (raw/adjusted): 7.00 / 5.831
   Impacts (raw/adjusted): 9.00 / 4.734
   Potential distribution (raw/adjusted): 8.00 / 4.208

Feasibility of Control: 167.77 (High)
   Control costs (raw/adjusted): 6.00 / 5.454
   Current distribution (raw/adjusted): 5.00 / 5.000
   Persistence (raw/adjusted): 8.00 / 6.152

Result: Targeted control, improve general weed management

Invasiveness

A1. What is the ability of the plant to establish amongst intact native environments?
Answer: Very High

Comments: 
There are large numbers of naturalised juvenile plants in the Mitchell Plateau area (Kimberley). They are only in areas that are protected by fire (A. Mitchell, AQIS, pers. comm. 2007).

African mahogany has the potential to colonise the edges of rainforest remnants in tropical climates (Csurhes & Edwards 1998).

K. senegalensis is generally a light demanding species although it will tolerate up to 50% shade when immature (CAB International 2000).

K. senegalensis is considered a sleeper weed (WWF Australia 2006).

Randall (2002) lists the status of this species in parts of the world as a ‘weed, sleeper weed, naturalised, environmental weed, [and] cultivation escapee’ (Bristow & Skelton 2004, Randall 2002).

A2. What is the reproductive ability of the plant?

(a) Time to seeding
Answer: >3 yrs/never

Comments: 
Survey results show that all trees over 10 years old were flowering and setting seeds, and probably annually, and that no flowering was observed on trees less than 10 years old. This is much younger than the report that trees begin to set seed after 20-25 years (Bristow & Skelton 2004, CAB International 2000).

(b) Annual production of viable seed /m2 or /plant
Answer: High

Comments: 
42 per m2 in adult trees (CAB International 2000).

(c) Vegetative reproduction
Answer: None

Comments: 
No evidence of natural vegetative reproduction around Darwin (NT Weed Risk Management Committee 2007).

Reproduces by vegetative fragmentation (Pacific Island Ecosystems at Risk 2005).

Regeneration is favoured in clearings, the species develops stool sprouts and root suckers (CAB International 2000).

Seed of this species is rarely available so an alternative means of planting stock-production by stem cuttings using juvenile shoots of hedged seedlings has been developed (Limpiyaprapant et al. 1996).

A3. Do propagules of the plant have properties that allow them to be dispersed long-distance by natural means?

(a) Flying animals (birds, bats)
Answer: No

Comments: 

(b) Other wild animals
Answer: No

Comments: 

(c) Water
Answer: Yes

Comments: 
This survey emphasises a risk associated with planting K. senegalensis in close proximity to wetter areas. If seed is transported away from the planting site by overland flow into a riparian area or irrigation drainage lines, it could develop unnoticed. Monitoring and management is essential…where seed might be washed into watercourses and become invasive in riparian strips, the natural habitat of this species (Bristow & Skelton 2004).

(d) Wind
Answer: Yes

Comments: 
The seeds are brown and flattened, about 2 x 2.5 cm with winged margins (Joker & Gamene 2003).

The seeds are dispersed by wind and may be carried away as far as 100 m (Joker & Gamene 2003).

A4. How likely is long-distance dispersal by human-assisted means?

(a) Deliberate spread by people
Answer: Common

Comments: 
Khaya senegalensis is currently being grown in plantations in the Northern Territory (Robertson (2006).

This species is widely grown as a street tree (Pacific Island Ecosystems at Risk 2005).

In Australia, it has been planted as a street tree around Darwin since the late 1950’s (Arnold 2004, Robertson 2006).

According to the ‘Aussie Plant Finder 2004’, it is available for sale in NT and Qld (WWF Australia 2006).

(b) Accidentally by people and vehicles
Answer: Unlikely

Comments: 

(c) Contaminated produce
Answer: Unlikely

Comments: 
Propagules are unlikely to disperse as a produce contaminant (Pacific Island Ecosystems at Risk 2005).

(d) Domestic/farm animals
Answer: Unlikely

Comments: 

Impacts

B1. What is the plant's competitive potential?
Answer: Medium

Comments: 
Natural regeneration from the seed is poor but does occur from suckers (IUCN 1998).

It is one of most drought-tolerant Khaya species but prefers moist sites and this seems to be more important for growth than nutrient availability (Joker & Gamene 2003).

It is a medium-sized to large tree (up to 30m) with a wide crown. This has the effect of shading out competition (Arnold 2004).

Mostly the responses to the survey stated that regeneration was not vigorous, or that germinant vigour was 'poor less than 15cm tall, less than 1 yr old'. With comments like : “In almost every example I have seen, 98% annual mortality from drought, parent/weed competition or plantation management occurs every year.” There were a couple of answers from NT respondents that vigour of the regeneration “depends on timing of dispersal”, and that it can be “very persistent”, and another that said regeneration was “vigorous on edge of the stand, and surviving perhaps 1-6 years (Bristow & Skelton (2004).

Regeneration is seen under older, larger trees, and this regeneration is generally restricted to close proximity of the parent tree. Regeneration mostly perishes within 12 months (Bristow & Skelton 2004).

It can be fast growing in a range of conditions in northern Australia (Nikles et al. 2004).

During the first year of growth, the seedling develops a strong, deep taproot, which makes it the most drought hardy of all the Khaya species. It is also very resistant to flooding (Robertson 2006).

B2. What is the plant’s potential to modify the existing fire behaviour and alter the fire regime?
Answer: Some potential

Comments: 
Saplings are very sensitive to fire but adult trees are relatively resistant (Joker & Gamene 2003).

Does not create a fire hazard in natural ecosystems (Pacific Island Ecosystems at Risk 2005).

Khaya senegalensis will not tolerate fire, and fire appears the main cause of death in most Queensland plantings (Bristow & Skelton 2004, CAB International 2000, Pacific Island Ecosystems at Risk 2005).

B3. What is the plant’s potential to restrict the physical movement of people, animals, vehicles, machinery and/or water?
Answer: Low

Comments: 
Does not form dense thickets: “natural regeneration from seed is poor” (Pacific Island Ecosystems at Risk 2005).

B4. What is the plant’s potential to negatively affect the health of animals and/or people?
Answer: Low

Comments: 
In some African countries, K. senegalensis is used for fodder for cattle and camels, though it is not very palatable (Pacific Island Ecosystems at Risk 2005).

Human inhabitants in K. senegalensis’s natural range also value the tree for its medicinal values (Arnold 2004).

Darwin City Council is expected to spend $175,000 over the next 15 months, cutting down and pruning dozens of dangerous trees. There is a risk of a branch coming down and hitting a child (NT News 2007).

B5. Does the plant potentially have negative effects on natural and cultural values?

(a) Reducing habitat quality for native animals?
Answer: Medium

Comments: 
No known effect on habitat quality (J. Woinarski, NT Biodiversity Unit, pers. comm. 2007).

(b) Threatened species or communities
Answer: None identified

Comments: 
No known effect on habitat quality (J. Woinarski, NT Biodiversity Unit, pers. comm. 2007).

(c) Sites of natural or cultural significance
Answer: None identified

Comments: 
No known effect on habitat quality (J. Woinarski, NT Biodiversity Unit, pers. comm. 2007).

B6. Is the plant presumed to have negative effects on environmental health?

(a) Soil chemistry/stability
Answer: Do not know

Comments: 
There are some concerns that as a large tree it could potentially affect nutrient levels (NT Weed Risk Management Committee 2007).

(b) Water quality
Answer: No

Comments: 

(c) Hydrology
Answer: Yes

Comments: 
Khaya senegalensis would likely have hydrological impacts given its size, deep tap-root and drought resistant qualities (NT Weed Risk Management Committee 2007, Robertson 2006).

Potential distribution

C1b. What is the Climatch suitability score (which indicates the proportion of the NT environment that is suitable for the plant)?
Answer: 3

Comments: 
The CLIMATCH model used by the NT Weed Management Branch predicts that 33% of the Northern Territory is climatically suitable for Khaya senegalensis (NT Weed Management Branch 2007).

Climatic requirements: Mean annual rainfall 700-1750 mm. Dry season duration: 2- 8 months (CAB International 2000).

A mahogany species, widespread in high-rainfall savannah woodland (IUCN 1998).

It occurs in riverine forests and scattered in high-rainfall savannah woodland. It grows at 0-1800m altitude in areas with 700-1750 mm rain/year and a dry season of 4-7 months (Joker & Gamene 2003).

In more moist areas, it is found in uplands, but is restricted to riparian habitats that extend into the savannah in the dryer portions of the range. Its distribution extends from Senegal to the Congo in West Africa, and across the continent to Sudan and Uganda (Arnold 2004).

In its natural habitat K.senegalensis is often found individually, dispersed in natural vegetation and secondary forest. It grows mainly in the riverine forests and deciduous savannah woodland, where it is a smaller tree reaching heights of 15m to 24m with a diameter of up to about 1m. The natural range of African Mahogany is in Africa between 8° and 15°N in a discontinuous band extending from the Atlantic Ocean eastwards towards the Indian ocean…Its habitats vary in altitude from 0-1800m asl with rainfalls varying from about 400mm to more than 1700mm per year and with dry seasons lasting from 4 to 8 months (Arnold et al. 2004).

C2. How many broad habitat types in the NT will the plant potentially naturalise in (up to 5)?
Answer: Three

Comments: 
There is photographic evidence of African mahogany invading savanna woodland in the NT (J. Page, Greening Australia, pers. comm. 2007).

The broad vegetation types in the Northern Territory that Khaya senegalensis will potentially naturalise in are:
   - Tropical riparian
   - Tropical open forests, savanna woodlands
   - Rainforests (at least the edges)

Of these, the favoured habitat type is tropical riparian (NT Weed Risk Management Committee (2007, Rossiter-Rachor et al. 2013).

C3. What is the potential of the plant to occur throughout its favoured habitat in the NT (as identified in question 2)?
Answer: Some

Comments: 
Has the potential to occur through some of its favoured habitat (NT Weed Risk Management Committee 2007).

Control costs

A1. How detectable is the weed?

(a) Distinguishing features
Answer: Always distinct

Comments: 
Always distinct (P. Jeffery & M. Fuller, pers. comm. 2007).

A tree with shining foliage, up to 100ft. high, with wide dense crown and thick stem; sepals pale green; petals and staminal tube cream, the latter suffused pink below; stigma yellow. Flowers normally 4-merous; ovary tapering into a slender style; fruit normally 4-valved, 4-6cm in diameter (Hutchinson & Dalziel 1958, Pacific Island Ecosystems at Risk 2005).

Cultivated timber tree to 30m with odd-pinnate leaves to 25cm long, the leaflets oblong-elliptic to 10cm long, loose sprays of white flowers and 4-valved woody capsules with winged seeds (Robertson 1989).

(b) Active growth period
Answer: >8 months

Comments: 
The active growth period is >8 months in both the Darwin and Katherine Weed Management regions (P. Jeffery & M. Fuller, pers. comm. 2007).

(c) Height at maturity
Answer: >2 m

Comments: 
A deciduous tree, 15-20m tall, reaching up to 35m on fertile soils…the timber is rated as one of the best African mahogany woods (Joker & Gamene 2003).

In its natural habitat it is a medium-sized to large tree (up to 30m) with a wide crown. In cultivation as an exotic it can grow up to more than 35 m high (Arnold 2004).

A2. What is the general accessibility of infestations at the optimum treatment time?
Answer: Medium

Comments: 
Most African mahogany are readily accessible. They are often found in riparian areas. The only problem is that you need to get large machinery in to chop them out (P. Jeffery & M. Fuller, pers. comm. 2007).

A3. How expensive is control of the weed in the first year of targeted control, for an infestation that has reached maximum weed density?

(a) Chemical costs
Answer: High

Comments: 
African mahogany chemical control costs would be in the high category (P. Jeffery & M. Fuller, pers. comm. 2007).

You need to treat the tree using the basal bark method using access and diesel (P. Jeffery & M. Fuller, pers. comm. 2007).

(b) Labour cost
Answer: High

Comments: 
African mahogany labour control costs would be in the high category (P. Jeffery & M. Fuller, pers. comm. 2007).

(c) Equipment cost
Answer: Low

Comments: 
African mahogany would be controlled using a knap sack sprayer. [Note: This equipment would place African mahogany control in the low equipment costs category] (P. Jeffery & M. Fuller, pers. comm. 2007).

Most infestations are not that big, and only the big tress would have high equipment costs (P. Jeffery & M. Fuller, pers. comm. 2007).

A4. What is the general community perception of this weed within the region?
Answer: Medium

Comments: 
The general community motivation to control African mahogany is medium. People are aware that African mahogany has an impact, especially after the last few cyclones that we have had (P. Jeffery & M. Fuller, pers. comm. 2007).

Current distribution

B1. What is the current pattern of the species’ distribution across the weed management region?
Answer: Scattered

Comments: 
African mahogany’s distribution in the Darwin and Katherine region is scattered (P. Jeffery & M. Fuller, pers. comm. 2007).

Examples of places where it has naturalised are: - Adelaide River - Upstream in the Katherine River (with Neem trees) - RAFF base Tindall - Batchelor behind the hotel - Giraween road. There places are not all disturbed areas. It can definitely invade intact environments (P. Jeffery & M. Fuller, pers. comm. 2007).

Persistence

C1. How long will it take to reach the maintenance period?
Answer: Medium

Comments: 
It is likely to take greater than 2-5 years to reach the maintenance period. Any woody weed will need at least this (P. Jeffery & M. Fuller, pers. comm. 2007).

C2. What is the minimum time period for reproduction of sexual or vegetative propagules?
Answer: >2 years

Comments: 
The minimum time for reproduction is greater than two years (P. Jeffery & M. Fuller, pers. comm. 2007).

Trees begin to produce seed after 20-25 years (CAB International. 2000).

Survey results show that all trees over 10 years old were flowering and setting seeds, and probably annually, and that no flowering was observed on trees less than 10 years old. This is much younger than the suggested 20-25 years by CAB international (2000) (Bristow & Skelton 2004).

C3. What is the maximum longevity of sexual or vegetative propagules?
Answer: 2-5 years

Comments: 
We don’t know what the maximum longevity of African mahogany propagules would be (P. Jeffery & M. Fuller, pers. comm. 2007).

In a recent study in Burkina Faso seeds were stored at -18, 3-5 and 25°C. The results showed that the seeds retain full viability regardless of storage temperature for at least two years. The seeds are sometimes heavily attacked by larvae and packing with CO2 can be necessary (Joker & Gamene 2003).

C4. What is the threat of reinfestation from outside the management region?

(a) Long-distance (>100m) dispersal by natural means
Answer: Occasional

Comments: 
This survey emphasises a risk associated with planting K.senegalensis in close proximity to wetter areas. If seed is transported away from the planting site by overland flow into a riparian area or irrigation drainage lines, it could develop unnoticed. Monitoring and management is essential…where seed might be washed into watercourses and become invasive in riparian strips, the natural habitat of this species (Bristow & Skelton 2004).

The seeds are brown and flattened, about 2 x 2.5 cm with winged margins (Joker & Gamene 2003).

The seeds are dispersed by wind and may be carried away as far as 100 m (Joker & Gamene 2003).

(b) Long-distance (>100m) dispersal by human means
Answer: Frequent

Comments: 
This species is widely grown as a street tree (Pacific Island Ecosystems at Risk 2005).

In Australia, it has been planted as a street tree around Darwin since the late 1950’s (Robertson 2002, Arnold 2004).

African Mahogany (Khaya senegalensis) produces one of the world’s primary cabinet timbers and is a close relation to Australia’s Red Cedar (Toona ciliata). Khaya senegalensis has been planted on many semi-dry sites across Northern Australia, as individuals or in small plots of mixed species as well as in single species plantings (Pacific Island Ecosystems at Risk 2005).

According to the ‘Aussie Plant Finder 2004’ it is available for sale in NT and Qld (WWF Australia 2006).

Propagules are unlikely to disperse as a produce contaminant (Pacific Island Ecosystems at Risk 2005).

References

Arnold R (2004). 'Khaya senegalensis - current use from its natural range and its potential in Sri Lanka and elsewhere in Asia'. In: Prospects for high-value hardwood timber plantations in the 'dry' tropics of northern Australia (eds D.I. Bevege, M. Bristow, D. G. Nikles and D. J. Skelton). Proc. of a Workshop held 19-21 October, 2004, Mareeba, Queensland. Published as a CD-ROM by Private Forestry North Queensland Association Inc., Kairi, Qld. Arnold R, Reilly D, Dickinson G & Jovanovic T (2004). 'Determining the climatic suitability of Khaya senegalensis for plantations in Australia'. In: Prospects for high-value hardwood timber plantations in the dry tropics of northern australia (eds D. I. Bevege, M. Bristow, D. G. Nikles and D. J. Skelton). Proc. of a Workshop held 19-21 October, 2004, Mareeba, Queensland. Published as a CD-ROM by Private Forestry North Queensland Association Inc., Kairi, Qld. Bristow M & Skelton D (2004). 'Preliminary weed risk assessment for Khaya senegalensis in plantations in northern Australia'. In: Prospects for high-value hardwood timber plantations in the 'dry' tropics of northern Australia (eds D. I. Bevege, M. Bristow, D. G. Nikles and D. J. Skelton). Proc. of a Workshop held 19-21 October, 2004, Mareeba, Queensland. Published as a CD-ROM by Private Forestry North Queensland Association Inc., Kairi, Qld. Centre for Agricultural Bioscience International (2000). Forestry Compendium Global module. Wallingford, UK. Csurhes, SM & Edwards, R (1998). Potential environmental weeds in Australia: candidate species for preventative control, Queensland Department of Natural Resources, Brisbane. IUCN (1998). The IUCN Red List of Threatened Species: Khaya senegalensis, viewed 14/03/2007, <http://www.iucnredlist.org/search/details.php/32171/summ>. Additional reference available on request from weedinfo@nt.gov.au.