Jacaranda mimosifolia
(jacaranda)

J. mimosifolia is a striking ornamental tree characteristic of many cities in tropical and sub-tropical countries, well-known for its clusters of striking bell-shaped, blue-violet flowers. Native to South America, like many ornamental trees, it was very widely introduced over the centuries. This species has naturalized in a number of countries and has been reported as invasive in a number of locations; Queensland, Australia, Hawaii, Chile’s Juan Fernandez Islands and in Kenya, Tanzania, South Africa and Zambia. J. mimosifolia is a fast growing tree that re-sprouts easily if damaged. It is deep-rooted and competitive and few plants or crops can grow beneath it once it has established. It can form thickets of seedlings beneath planted trees from which the species may expand and exclude other vegetation thereby decreasing biodiversity in an area. 

J. mimosifolia is considered to be native to a well-defined area in central and eastern South America, including Uruguay, parts of Argentina (Entre Rios, Jujuy, Salta, Tucuman), Paraguay (Alto Paraguay, Cordillera) and as far as Bolivia (USDA-ARS, 2014). According to the IUCN (2016) and their red list of threatened species, J. mimosifolia is recorded as vulnerable in its native range. It is threatened here as the forests in which it typically occurs are being converted for agriculture (IUCN, 2016).

J. mimosifolia has however been very widely introduced pantropically as an ornamental for its showy blue-violet flowers and is likely to be present in most tropical regions, i.e. many more countries than those indicated in the Distribution table. It has become naturalized in a number of countries, including elsewhere in South America, but is reported as invasive only in South Africa, Australia, Hawaii and Chile’s Juan Fernandez islands.

In Australia, J. mimosifolia is widespread in south-eastern Queensland, with isolated occurrences in most other states (Council of Heads of Australasian Herbaria, 2014) though it is not yet a serious problem. J. mimosifolia has proved to be a significant and successful invader in northern and eastern South Africa and a current estimate is that is has “invaded about 1.8 million ha, but mainly at very low densities" (David Le Maitre, CSIR, South Africa, personal communication, 2014). It is present throughout east Africa (Dharani, 2005) and is naturalized there in parts, e.g. in Ngorongoro, Tanzania (Henderson, 2002).

The majority of records of J. mimosifolia being introduced into a new area come as the plant is intentionally introduced for its ornamental purposes. As such a risk assessment in the Pacific scored J. mimosifolia 1, indicating that it posed only a very low risk of future invasion (PIER, 2014). Nevertheless J. mimosifolia has been listed as a Category 3 invader in South Africa (Henderson, 2001), meaning that no further planting or trade in propagative material is allowed, except with special permission and existing plants must be prevented from spreading.

J. mimosifolia has been observed as becoming naturalized mainly in drier or mesic areas (PIER, 2014), in savanna and other grasslands, riparian woodland and other riverside habitats, also in forests and in sheltered situations such as in wooded ravines.

Genetics

The chromosome number of J. mimosifolia is recorded as 2n=36 by Piazzano (1998).

Reproductive Biology

J. mimosifolia is self-incompatible and depends on a range of insects for pollination, including bees of medium or large size (Alves et al., 2010). The pattern of anthesis and stigma receptivity of J. mimosifolia was reported in India (Battacharjee and Sareen, 1991). Pods dry on the tree and split after about a year, releasing the seeds. Fresh seed has a germination capacity of 50-92% and generally no seed pre-treatment is required. The optimum temperature for germination is 25°C and there is a slightly higher rate of germination in light than in dark (Socolowski andTakaki, 2004). Seeds remain viable for at least 12 months in dry storage (Useful Tropical plants, 2016). It is also possible for J. mimosifolia to become established from cuttings.

Physiology and Phenology

For intentional planting, seedlings need considerable care during the first two years, requiring weeding, regular watering and staking until well established. They can be fast growing on good sites achieving 3 m per year during the first two years and 1 m per year in subsequent years. Established trees respond well to light coppicing. If used as an ornamental, an open environment or large spacing is required for this light-demanding species with its wide canopy. Trees flower from September to November in South Africa.

Environmental Requirements

J. mimosifolia is native to areas having a temperate mesothermal climate with a marked dry season. In tropical regions it grows best in highland areas up to 2400 m with an annual rainfall of 900-1300 mm, but will also tolerate rainfall up to 2000 mm. It does not tolerate frost. This species grows well on well-drained sandy loam soils, although it will survive on poorer shallow soils. The species does not tolerate waterlogged or clay soils. 

A number of diseases have been reported on J. mimosifolia, including the honey fungus Armillaria heimii (Paterson and Mwangi, 1996) and Mundulla yellows (Mundulla Yellows dieback).

Pests of J. mimosifolia include Planococcus kenyae (coffee mealybug), Nipaecoccus viridis (spherical mealybug) and Orthezia insignis [Insignorthezia insignis] (greenhouse orthezia) the latter reported to have killed a quarter of all J. mimosifolia seedlings in a nursery in India (Siddappaji et al., 1986). Additionally, Cuscuta cassytoides caused high mortality in a nursery in Tanzania (Hocking, 1966) and the Jacaranda leaf-miner, Phytoliriomyza jacarandae, was reported as a recent arrival in South Africa in 1997 (Neser, 1997). The African mistletoe Erianthemum ulugurense [Erianthemum schelei] has also been reported on J. mimosifolia in Kenya (Omunyin and Wabule, 1996).

Animal feed, fodder, forage

• Invertebrate food

Environmental

• Amenity
• Landscape improvement
• Ornamental
• Windbreak

Fuels

• Fuelwood

General

• Ornamental

Human food and beverage

• Honey/honey flora

Materials

• Carved material
• Pesticide
• Wood/timber

Medicinal, pharmaceutical

• Source of medicine/pharmaceutical
• Traditional/folklore

Roundwood

• Building poles
• Posts

Sawn or hewn building timbers

• Carpentry/joinery (exterior/interior)
• For light construction

Woodware

• Industrial and domestic woodware
• Tool handles
• Wood carvings

Based on foliage, young plants of J. mimosifolia could be confused with a variety of other species. However, the characteristic flowers mean that mature trees cannot be mistaken and even after flowering, the round, flat pods make the tree stand out. The similarity of foliage and form and use as a common ornamental street tree means that J. mimosifolia and Delonix regia can sometimes be confused when there are no flowers or fruit. However, both are highly distinct, with mauve-blue-violet flows and round pods in J. mimosifolia compared to red-yellow flowers are long pods (often 50 cm or more) in D. regia.

Due to the variable regulations around (de)registration of pesticides, your national list of registered pesticides or relevant authority should be consulted to determine which products are legally allowed for use in your country when considering chemical control. Pesticides should always be used in a lawful manner, consistent with the product's label.

Mechanical Control

It is possible for young seedlings of J. mimosifolia and small plants to be hand pulled (PIER, 2014).

Chemical Control

For larger J. mimosifolia trees, they should be cut and herbicide should be applied to the stumps (PIER, 2014). Henderson (2001) reports that J. mimosifolia is very difficult to control once it is established and that large tree must be ring-barked or cut down below ground level and any regrowth treated with herbicide. Effective herbicides include imazapyr or glyphosate.

Little is known about the ecology of J. mimosifolia, especially regarding its reproduction and seed dispersal and more work is required to assess the impacts of invasion and means for effective control of the species.

09/06/2014 Original text by:

Nick Pasiecznik, Agroforestry Enterprises, France