Indigofera spicata
(creeping indigo)

Pictures

Picture	Title	Caption	Copyright
Title Habit Caption Indigofera spicata (creeping indigo); habit and flowers in Laysan albatross breeding colony. Nimitz Ave., Sand Island, Midway Atoll, Hawaii, USA. June, 2008. Copyright ©Forest Starr & Kim Starr - CC BY 4.0	Habit	Indigofera spicata (creeping indigo); habit and flowers in Laysan albatross breeding colony. Nimitz Ave., Sand Island, Midway Atoll, Hawaii, USA. June, 2008.	©Forest Starr & Kim Starr - CC BY 4.0
Title Habit Caption Indigofera spicata (creeping indigo); habit, showing leaves, flowers and seedpods, in old macadamia nut orchards. Waiehu, Maui, Hawaii, USA. February, 2007. Copyright ©Forest Starr & Kim Starr - CC BY 4.0	Habit	Indigofera spicata (creeping indigo); habit, showing leaves, flowers and seedpods, in old macadamia nut orchards. Waiehu, Maui, Hawaii, USA. February, 2007.	©Forest Starr & Kim Starr - CC BY 4.0
Title Flower spike and leaves Caption Indigofera spicata (creeping indigo); flower spike and leaves. Honokanaia, Kahoolawe, Hawaii, USA. December, 2008. Copyright ©Forest Starr & Kim Starr - CC BY 4.0	Flower spike and leaves	Indigofera spicata (creeping indigo); flower spike and leaves. Honokanaia, Kahoolawe, Hawaii, USA. December, 2008.	©Forest Starr & Kim Starr - CC BY 4.0
Title Leaves and seedpods Caption Indigofera spicata (creeping indigo); leaves and seedpods. Honokanaia, Kahoolawe, Hawaii, USA. December, 2008. Copyright ©Forest Starr & Kim Starr - CC BY 4.0	Leaves and seedpods	Indigofera spicata (creeping indigo); leaves and seedpods. Honokanaia, Kahoolawe, Hawaii, USA. December, 2008.	©Forest Starr & Kim Starr - CC BY 4.0

Identity

Preferred Scientific Name

• Indigofera spicata Forssk.

Preferred Common Name

• creeping indigo

Other Scientific Names

• Indigofera endecaphylla sensu auct., orth. var., non Jacq.
• Indigofera hendecaphylla sensu auct., non Jacq.

International Common Names

• English: indigo; spicate indigo; trailing indigo
• Spanish: añil rastrero
• French: indigotier rampant
• Chinese: sui xu mu lan

Local Common Names

• Brazil: amendoim-bravo
• Germany: Kriechender Indigostrauch
• Indonesia: basingan
• Indonesia/Sulawesi: baleh angin
• Indonesia/Sumatra: sibar
• Madagascar: aika; egitra; engitra; sindahoripotsy
• Thailand: khram-khrua (northern)
• USA/Hawaii: `iniko; `inikoa; indigo; kolu

Summary of Invasiveness

I. spicata is native to Africa, Madagascar and throughout South and Southeast Asia, and was introduced to the Americas in tropical areas as a cover crop (Duke, 1981; Sunarno, 1997). I. spicata may potentially threaten native flora, as it will send out trailing stems reaching up to 3 m long, producing numerous adventitious roots at the nodes and smothering other weeds (Morton, 1989; Sunarno, 1997). 

I. spicata received a score of 6 in a risk assessment prepared for Australia, indicating its potential invasiveness but recommending further research (PIER, 2014). It is listed in the Global Compendium of Weeds as an ‘agricultural weed’, ‘naturalised’ and ‘environmental weed’ (Randall, 2012). I. spicata is invasive to many parts of Asia and the Pacific, including French Polynesia (Marquesas Islands, Society Islands., Austral Islands), the Cook Islands (Mangaia), Micronesia (Pohnpei and Nauru), New Caledonia, Hawaii, Singapore, Japan, and Taiwan (Wagner et al, 1999; Chong et al, 2009; PIER, 2014; Flora of Taiwan Editorial Committee, 2014; Goka, 2014). Other tropical places where it is a known weed include Australia, Puerto Rico and adjacent islands, the United States (southern Florida), French West Indies (Guadeloupe), and Mexico (Villasenor and Espinosa-Garcia, 2004; Randall, 2012).

Taxonomic Tree

• Domain: Eukaryota
•     Kingdom: Plantae
•         Phylum: Spermatophyta
•             Subphylum: Angiospermae
•                 Class: Dicotyledonae
•                     Order: Fabales
•                         Family: Fabaceae
•                             Subfamily: Faboideae
•                                 Genus: Indigofera
•                                     Species: Indigofera spicata

Notes on Taxonomy and Nomenclature

Indigofera is the largest genus of the tribe Indigofereae, in the Fabaceae (Leguminosae) family, containing over 700 species found in the tropics and subtropics (Puy et al, 2002). Linnaeus (1753) described the genus based on the three species of I. tinctoria, I. hirsuta and I. glabra, with the name Indigofera referring to the indigo dye produced by members of the genus. 

Indigofera hendecaphylla Jacq. and I. spicata Forssk. were long considered to be synonymous. In 1993, Puy et al published a paper showing I. spicata Forssk. and I. hendecaphylla Jacq. to be two separate species, which is widely accepted today (Puy et al, 1993; Farida Hanum and Maesen, 1997; Wagner et al, 1999; Wilson and Rowe, 2008; Missouri Botanical Garden, 2014; The Plant List, 2014). According to Puy et al., I. hendecaphylla is more widespread throughout the Old World tropics and subtropics to the Pacific Islands, whereas I. spicata refers to the more restricted species, confined to Africa, Yemen, Madagascar and the Mascarenes, extending into drier areas where I. hendecaphylla does not occur (Puy et al, 1993). Previous literature attributing toxicity and stock poisoning to I. spicata may only refer to I. hendecaphylla (Verdcourt and Trump, 1969; Puy et al, 1993; Wilson and Rowe, 2008, ILDIS, 2014). However, because of the considerable variation in both species and within species varieties, genetic and transplanting data are recommended before recognizing infra-specific taxa (JSTOR, 2013). Caution is advised when interpreting previous specimens and literature, particularly on toxicity and stock poisoning, as this may refer to either I. spicata or I. hendecaphylla, or both.

For the purposes of this datasheet, I. spicata and I. hendecaphylla are considered one species.

Description

The following is taken from Puy et al, 2002: A perennial prostrate creeping herb; stems radiating from a central woodstock, often somewhat flattened, thinly strigose; biramous hairs medifixed, white, stiff, appressed; stipules triangular, finely tapering, 4-6 mm long, the base partially sheathing the stem, with broad, scarious and glabrous margins; stipels absent or minute and laciniate. Leaves with (3-)5-7 alternate leaflets; rachis flattened; leaflets obovate, cuneate in the basal half, the terminal leaflet not much larger than the laterals, 4-15 x 3-6 mm, sparsely strigose to glabrous above and strigose beneath. Racemes pedunculate, ascending, dense, 15-100 mm long; bracts c.2 mm long, caduceus. Flowers 3-4 mm long, the wings longer than the keel, pink, the standard with a white basal eye and paler behind. Calyx c. 3 mm long, about as long as the staminal sheath, strigose; teeth subulate, twice as long as the tube. Standard glabrous except for the strigose apex; keel apex acute. Staminal sheath c. 3 mm long (about as long as the calyx). Ovary strigose. Pods often numerous and dense, deflexed, linear-oblong, straight, (12-)15-20 mm long, not constricted between the seeds when mature, sparsely strigose, pale straw brown, eventually splitting into two spiraling valves, with 7-9 seeds. Seeds c. 1 x 1 mm, cuboid, smooth.

Plant Type

Distribution

Several disagreements in distribution for I. spicata were found between sources. In Java, the species is reported as native according to ILDIS (2014), but Morton (1989) reports that it was introduced to Java in 1923, with Sampson (1928) reporting novel cultivation efforts in Java in 1925 and 1926. On the French Polynesian island of Tahiti, the species is reported as native by USDA-ARS (2013), but it is an introduced invasive species according to PIER (2014). It is listed as native in the Philippines by some sources (USDA-ARS, 2013; ILDIS, 2014), but this is apparently a mistake, as it was reported by Merrill (1919) as introduced to the country by 1918, with Morton (1989) reporting its introduction from Java to the Philippines as a cover crop in 1927. It is also mistakenly listed as native and endemic to Brazil (Forzza et al, 2012). Some of these discrepancies may be due to the varied name use of I. spicata when describing I. hendecaphylla,I. spicata, or both.

Distribution Table

The distribution in this summary table is based on all the information available. When several references are cited, they may give conflicting information on the status. Further details may be available for individual references in the Distribution Table Details section which can be selected by going to Generate Report.

History of Introduction and Spread

I. spicata is native to Africa, Madagascar, Southern and Southeast Asia, and has naturalized across tropical regions. It was introduced into Java in 1923 as a nitrogen-fixing cover crop for coffee, tea, rubber, oil palm, and sisal plantations (Morton, 1989). According to Morton (1989) cultivation of the plant spread from Java to the Philippines in 1927, but the species was actually first recorded (as I. hendecaphylla) in the country in 1918 (Merrill, 1919). It was introduced to Hawaii prior to 1949; while the species was not included in Hoakasa and Thistle’s 1954 Noxious plants of the Hawaiian Ranges, by 1965 it was known as a good ground cover although not for fodder, and has now naturalized (Morton, 1989; Wagner et al, 1999). 

I. spicata was introduced from southern India to Ceylon and was first grown at Peradeniya in 1921 (Sampson, 1928). The species was then introduced from Ceylon to Gainesville, Florida, United States in 1925 as a cover crop and forage plant, and from there was brought to the Neotropics (Morton, 1989). It was introduced into Jamaica in 1933 to smother weeds in orchards, and taken to Mayaguez, Puerto Rico, in 1937 for planting as green manure, a soil binder, and forage for cattle, but soon became considered a weed after it was found to have toxic effects on cattle and other grazing animals (Morton, 1989). In 1979, it was collected on the other side of Puerto Rico (Carite) showing a rapid colonization of the island. Nowadays, it is very common and naturalized in Puerto Rico (US National Herbarium). It was present in Guadeloupe by 1935 (US National Herbarium). The first record of the species in Dominica (as Indigofera hartwegii) is from 1989 (Nicholson, 1991), however, a reexamination of this collection showed it to refer to I. hendecaphylla. Despite its invasiveness and reported toxicity, I. spicata continues to be commonly used as a cover crop around the world today.

Risk of Introduction

The risk of introduction for I. spicata is moderate but not insignificant, as the species’ adaptability to various soil types and usefulness in erosion control, crop cover and green manures has led to its widespread cultivation and use across tropical regions around the world (Morton, 1989; USDA-ARS, 2013). The species spreads by seeds, which are numerous, viable, and easily dispersed by human, animal and bird movement, as well as by cuttings, which have been known to spread by commercial soil transfer and machinery such as lawn mowing and landscaping equipment (Morton, 1989). 

I. spicata was included in a 2008 checklist of the world’s poisonous plants and has been researched for its hepatoxic components that have caused abortion in cattle and are reportedly toxic to ponies, sheep, rabbits and other grazers (Hegarty and Pound, 1968; Verdcourt and Trump, 1969; Duke, 1981; Wagstaff, 2008; Ossedryver et al, 2013). In some neglected pastures, it can constitute far more than 50% of the forage, posing risk to grazing animals (Morton, 1989). 

I. spicata has moderate weed potential in New South Wales, Australia (Hosking et al., 2011). It was given a score of 6 for Australia (Further Research Needed) in a risk assessment of its potential invasiveness (PIER, 2014).

Habitat

I. spicata is generally found in disturbed grasslands, cultivated areas and waste places at altitudes between 0 and 2700 m, and can tolerate acidic and phosphorus-deficient soil (Duke, 1981). In Puerto Rico and the Virgin Islands, it is found in trails, roadsides, gardens and lawns (Mas and Lugo-Torres, 2013). In Nicaragua the species is occasional on dry slopes, grasslands and shrublands at altitudes of 130-1100 m (Missouri Botanical Garden, 2014). In Colombia, it is found at altitudes of 2000-2500 m, while in Bolivia at lower altitudes of 500-1000 m (Missouri Botanical Garden, 2014). It is found in Atlantic rainforests of Brazil (Forzza et al., 2012). In China, the species is found in open ground and moist, sunny trailsides at 800-1100 m altitudes (Flora of China Editorial Committee, 2014). In Hawaii, it was introduced as a pasture legume and is now naturalized in low elevation, dry, disturbed areas (Wagner et al., 1999).  In Madagascar, it is present in open, disturbed areas such as along roads, tracks and around villages, evergreen, humid forests at low (0-800 m) and lower montane (1800-2000 m) altitudes, as well as in deciduous and seasonally dry, western forests and coastal areas from 0-800 m (Puy et al., 2002).

Habitat List

Biology and Ecology

Genetics

The chromosome count for I. spicata is 2n=16, 32 (Duke, 1981; Missouri Botanical Garden, 2014). 

Reproductive Biology

The following is taken from Sunarno, 1997: The species can be propagated by seed and by stem cuttings. Seed is very hard and germinates poorly without scarification. Mechanical scarification and treatment with sulphuric acid for 40-60 minutes can increase the germination rate to about 80%. To obtain a good distribution of the seed it is mixed with sand or filtered dry soil at a ratio of seed to sand of 1:4 before sowing. If planted in rows 60 cm apart the seed rate is about 3.3 kg/ha. Cuttings are used when seed is difficult to obtain. For large-scale plantings, they should be raised in nurseries. Cuttings of about 20 cm long are planted at a spacing of 60 cm x 60 cm with 5 cuttings per hole. Once established, [I. spicata] is self-sowing. 

Growth and Development

Seedlings of I. spicata develop a strong taproot, which serves to loosen the soil. If cuttings are used for planting, the plant remains very low and cover rarely exceeds 12 cm in height. A fair cover can be established in 4-6 months and a continuous, even cover in a year from planting. The plants send out trailing stems which, under favourable conditions, may attain a length of 2-3 m and may produce roots from the nodes. Plants grow taller as they mature, and after two years are normally 30-40 cm tall. Vigorous regrowth occurs at the start of the rainy season (Morton, 1989; Sunarno, 1997). 

Associations

Like several other members of the Indigofera genus, I. spicata has been cultivated as green manure due to its capability of nitrogen-fixing symbiosis with rhizobia and bradyrhizobia (Sprent et al, 1987; Sunarno, 1997). 

Environmental Requirements

I. spicata may compete with and dominate the native flora, as it is well adapted to a wide range of soil types. The species thrives best on clay soils, but can tolerate various soil types including limestone, sandy, nutrient-poor and phosphorus-deficient soils as well as moderately acidic (pH 5.0-7.7) soils, and can grow at altitudes up to 2700 m (Duke, 1981; Puy et al, 2002; for altitudes in various countries, see Habitat section). It can reportedly tolerate an annual rainfall of 600-1500 mm, but may be found in wetter locations receiving up to 4000 mm annual rainfall and can grow following the onset of rain (FAO, 1977; Duke, 1981; Sunarno, 1997). In cultivation it is fairly resistant to drought, salt, and heavy rain (Morton, 1989). When grown under heavy shade, for example in rubber plantations, growth is poor (Sunarno, 1997). Regarding climate tolerances, the species ranges from Warm Temperate Moist through Tropical Moist Forest Life Zone (Duke, 1981). [Rainfall, temperature and pH levels in tables are from Duke, 1981].

Climate

Air Temperature

Rainfall

Soil Tolerances

Soil reaction

• acid
• alkaline
• neutral

Soil texture

• heavy
• light
• medium

Special soil tolerances

• other

Notes on Natural Enemies

While in 1981 I. spicata was reported to be “remarkably free of pests and disease” (Duke, 1981), newer research has shown two natural enemies from the plant and animal kingdom. Spodoptera littoralis (cotton leafworm), a parasitic insect, targets I. spicata as one of its host plants (CABI, 2013). I. spicata is also a host plant for the parasitic plant Striga gesnerioides (cowpea witchweed) which occurs in western Africa. 

In Sri Lanka, the only important pest of I. spicata is the caterpillar Dichomeris ianthes, which can sometimes totally defoliate the cover crop, although I. spicata usually recovers very quickly (Sunarno, 1997). In Peninsular Malaysia, the plant is a host of the larvae of a small moth, probably Lamprosema diemenalis, but again, the damage is not permanent (Sunarno, 1997).

Means of Movement and Dispersal

I. spicata is easily dispersed via vectors, accidental introduction, and intentional introduction. Some cultivars of I. spicata are grown for forage, despite being known as poisonous to grazing animals (Duke, 1981; Morton, 1989; Puy et al., 1993). The species seeds profusely and is easily propagated by both cuttings and by seed, and can provide a good cover for crops within 4-6 months. Seed rate is 1-2 kg/ha, with each kilo of seed containing up to 500,000 seeds. It can be killed with herbicide for minimum or zero tillage production of arable crops. (FAO, 1977). 

Morton (1989) reported I. spicata becoming a very common weed in lawns and parkways in Florida, spreading its runners over sidewalks in Greater Miami and its suburbs, due to the transportation of soil and sod for lawns from further north which carried the seeds and/or portions of roots or runners. It was also deduced that “mowing machines must carry the seeds from yard to yard…. Ornamental plant nurseries and home and commercial developments receive truckloads of soil from outlying pits north of Miami” (Morton, 1989). Further spread was observed by pets and horse movement, with an example of horseback riders crossing between community parks (Morton, 1989). I. spictata may also spread by water and in mud attached to animals and vehicles (Brisbane City Council, 2013).

Pathway Causes

Pathway Vectors

Impact Summary

Economic Impact

I. spicata has been widely spread in tropical regions around the world as a valuable cover crop and green manure, proving to be economically beneficial to farmers and their plantations (Duke, 1981; Morton, 1989). However, it may compete with the actual crop for resources as it tends to creep and has a deep taproot system (Nyamjom and Konyango, 2008).

I. spicata has also been evaluated for its hepatoxic components leading to the poisoning of cattle, livestock and wild animals that graze on it, which have led to its disuse in most places as intentional fodder (Hegarty and Pound, 1968; Verdcourt and Trump, 1969; Duke, 1981; Puy et al, 1993; Sunarno, 1997; Ossedryver et al, 2013). The species was also previously cultivated as a source of indigo dye, but this use has been largely discontinued since the emergence of synthetic dyes (Duke, 1981).

Environmental Impact

I. spicata has been valued as an effective cover crop, green manure and for erosion control, leading to its introduction from the Old World tropics to the Neotropics. It effectively controls soil erosion, even under heavy rainfall on slopes, hills and undulating land, and once the cover crop has been established, few weeds can grow (Sunarno, 1997). 

Given its invasiveness in several countries, and adaptability to a range of soils including nutrient-deficient types, I. spicata demonstrates risk potential to compete for and dominate space and resources over local and native biodiversity. The species was given a Risk Assessment score of 6 (Further Research Needed) for Australia, citing its particular characteristics of seed viability and a climbing or smothering growth habit (PIER, 2014). It was included in a 2008 checklist of international poisonous plants (Wagstaff, 2008), and has been largely disused as intentional fodder due to its abortive effects on cattle and toxicity to rabbits, sheep and other grazing animals (Duke, 1981). 

I. spicata is listed as an ‘agricultural weed’, ‘environmental weed’, ‘naturalised’ and ‘weed’ in the Global Compendium of Weeds (Randall, 2012) and is invasive to many parts of Asia and the Pacific, including French Polynesia (Marquesas, Society and Austral Islands), the Cook Islands (Mangaia), Micronesia (Pohnpei and Nauru), New Caledonia, Hawaii, Singapore, Japan, and Taiwan (Wagner et al, 1999; Chong et al, 2009; PIER, 2014; Flora of Taiwan Editorial Committee, 2014; Goka, 2014). Other tropical places where it is a known weed include Australia (New South Wales, Queensland, Northern Territory), Puerto Rico and adjacent islands, the United States (southern Florida), French West Indies (Guadeloupe), and Mexico (Villasenor and Espinosa-Garcia, 2004; Wilson and Rowe, 2008; Hosking et al, 2011; Randall, 2012; Brisbane City Council, 2013).

Risk and Impact Factors

• Proved invasive outside its native range
• Has a broad native range
• Abundant in its native range
• Highly adaptable to different environments
• Tolerates, or benefits from, cultivation, browsing pressure, mutilation, fire etc
• Pioneering in disturbed areas
• Highly mobile locally
• Benefits from human association (i.e. it is a human commensal)
• Fast growing
• Has high reproductive potential
• Has propagules that can remain viable for more than one year
• Reproduces asexually

• Ecosystem change/ habitat alteration
• Modification of nutrient regime
• Monoculture formation
• Negatively impacts animal health
• Reduced native biodiversity
• Threat to/ loss of endangered species
• Threat to/ loss of native species

• Competition - monopolizing resources
• Competition - smothering
• Herbivory/grazing/browsing
• Interaction with other invasive species
• Poisoning
• Rapid growth
• Rooting

• Highly likely to be transported internationally deliberately

Uses

I. spicata provides good soil cover for crops, smothering weeds as well as providing soil improvement (nitrogen fixing) and control against soil erosion. In Sri Lanka the species was the most popular green manure and cover crop on tea estates, while in Indonesia and Peninsular Malaysia it is used as a cover crop in rubber, sisal, oil palm and tea plantations, and in Africa in coffee plantations (Sunarno, 1997). Some varieties provide valuable and palatable fodder, particularly in Africa; however, leaves and seeds of other varieties are highly hepatotoxic and have been largely discontinued for intentional fodder (Duke, 1981; Sunarno, 1997). 

Like several other members of the genus, I. spicata was long cultivated as a source of indigo dye; however, with the rise of synthetic dye this use has been discontinued in most parts of the world (Duke, 1981; Sunarno, 1997).

Uses List

Animal feed, fodder, forage

• Fodder/animal feed

Environmental

• Erosion control or dune stabilization
• Soil improvement

Materials

• Dyestuffs
• Green manure

Similarities to Other Species/Conditions

I. spicata Forssk. and I. hendecaphylla Jacq. were long considered to be synonymous. In 1993 Puy et al. reported I. spicata and I. hendecaphylla to be two separate species. According to Puy et al., I. hendecaphylla is more widespread throughout the Old World tropics and subtropics to the Pacific Islands, whereas I. spicata refers to the more restricted species, confined to Africa, Yemen, Madagascar and the Mascarenes, extending into drier areas where I. hendecaphylla does not occur (Puy et al, 1993). The main morphological differences are:

• The staminal sheath of I. hendecaphylla is 4-5 mm long and distinctly exceeding the calyx, whereas the staminal sheath of I. spicata is 3-3.5 mm long, not or hardly exceeding the calyx in I. spicata.
• The leaves of I. hendecaphylla have 9-11 narrowly oblong-elliptic leaflets each, rarely any fewer, and glabrous or sparsely strigose on the upper surface. The leaflets of I. spicata are 5-8 in number, obovate and cuneate in the basal half, with the upper surface strigose and rarely subglabrous. 

However, considerable variation occurs in both species and within species varieties, and exceptions to these differences often occur (Puy et al., 1993; JSTOR, 2013). Previous literature in which both species are referred to as I. spicata has caused confusion regarding species distribution, invasiveness, and toxicity.I. spicata has been separated from I. hendecaphylla based on the work of Puy et al. and from the examination of collections deposited at the US National Herbarium. Both species are found in the West Indies; according to the collections so far analysed by the Herbarium, I. hendecaphylla is only found in some islands of the Lesser Antilles, while I. spicata is present in Jamaica, Puerto Rico, St. Thomas, and some of the Lesser Antilles. 

According to the Brisbane City Council (2013), in Australia I.spicata is considered similar to I. linnaei and I. linifolia, but both of these other species have much smaller pods (less than 7 mm long). I. spicata is also very similar to I. circinella. The main differences are:

• I. spicata has mostly creeping (prostrate) stems, and its stems and leaves are covered in close-lying hairs (appressed pubescent). Its cylindrical fruit are straight and borne in a backwards facing position (reflexed).
• I.circinella has mostly creeping (prostrate) stems, and its stems and leaves are hairless (glabrous) or covered in close-lying hairs (appressed pubescent). Its cylindrical fruit are strongly curved or coiled. Hairy indigo (Indigofera hirsuta) has spreading or upright (erect) stems, and its stems and leaves are covered in spreading hairs (hirsute). Its cylindrical fruit are straight and borne in a backwards facing position (reflexed) (Brisbane City Council, 2013). 

I. spicata has also been sometimes confused with Indigofera miniata Ortega (Missouri Botanical Garden, 2014).

Prevention and Control

I. spicata responds to herbicide treatment, which has been found to shrink the taproot so that it can be extracted more easily (Morton, 1989). An evaluation of the species for live mulch reported that it appeared to be suitable as a cover crop to be killed with herbicide for minimum or zero tillage production of arable crops (FAO 1977). In eastern Africa, repeated application of 2,4-D and MCPA are considered effective control measures (Nyamjom and Konyango, 2008). Similarly in Brisbane, Australia, herbicide application via foliar spray is recommended for weed control (Brisbane City Council, 2013).

Gaps in Knowledge/Research Needs

Further research is needed regarding the toxicity of I. spicata, particularly on the variation of the toxic compound indospicine within different varieties. Clarification between I. spicata and I. hendecaphylla is needed for the body of literature existing prior to the separation of I. spicata into the two species by Puy et al. (1993), as this is essential for understanding the distribution and invasiveness of the plant within different regions of the world. Likewise more research is needed on potential impacts of the species’ introduction, as well as detection, prevention and control measures to ensure it does not reach invasive status in the many places it has already naturalized.

References

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Brisbane City Council, 2013. Weed Identification Tool- Creeping Indigo. Queensland, Australia: Brisbane City Council. http://weeds.brisbane.qld.gov.au/weeds/creeping-indigo

Broome R; Sabir K; Carrington S, 2007. Plants of the Eastern Caribbean. Online database. Barbados: University of the West Indies. http://ecflora.cavehill.uwi.edu/index.html

CABI, 2013. Invasive Species Compendium. http://www.cabi.org/isc

Chong KY; Tan HTW; Corlett RT, 2009. A checklist of the total vascular plant flora of Singapore: native, naturalised and cultivated species. A checklist of the total vascular plant flora of Singapore. http://rmbr.nus.edu.sg/raffles_museum_pub/flora_of_singapore_tc.pdf

Duke JA, 1981. Handbook of legumes of world economic importance. New York, USA: Plenum Press, 345 pp.

Faridah Hannum I; Maesen LJGvan der, 1997. Plant Resources of South-East Asia No 11. Auxiliary Plants.

Flora Mesoamericana, 2014. Flora Mesoamericana. St. Louis, Missouri, USA: Missouri Botanical Garden. http://www.tropicos.org/Project/FM

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Flora of Taiwan Editorial Committee, 2014. Taiwan Plant Names. St. Louis, Missouri and Cambridge, Massachusetts, USA: Missouri Botanical Garden and Harvard University Herbaria. http://www.efloras.org/flora_page.aspx?flora_id=101

Forzza RC; Leitman PM; Costa AF; Carvalho Jr AA, et al. , 2012. List of species of the Flora of Brazil (Lista de espécies Flora do Brasil). Rio de Janeiro, Brazil: Rio de Janeiro Botanic Garden. http://floradobrasil.jbrj.gov.br/2012/

Funk V; Hollowell T; Berry P; Kelloff C; Alexander SN, 2007. Checklist of the plants of the Guiana Shield (Venezuela: Amazonas, Bolivar, Delta Amacuro; Guyana, Surinam, French Guiana). Contributions from the United States National Herbarium, 584 pp.

Goka K, 2014. List of Invasive Alien Species of Japan, Invasive Species of Japan website. Onogawa, Tsukuba, Ibaraki, Japan: National Institute for Environmental Studies. http://www.nies.go.jp/biodiversity/invasive/resources/listen_toc.html

HEGARTY MP; POUND AW, 1968. Indospicine, a new hepatotoxic amino-acid from Indigofera spicata. Nature, 217:354-355.

Hosking JR; Conn BJ; Lepschi BJ; Barker CH, 2011. Plant species first recognised as naturalised or naturalising for New South Wales in 2004 and 2005. Cunninghamia: A Journal of Plant Ecology for Eastern Australia, 12(1):85-114.

ILDIS, 2014. International Legume Database and Information Service. Reading, UK: School of Plant Sciences, University of Reading. http://www.ildis.org/

JSTOR, 2013. JSTOR Global Plants. Ann Arbor, MI and New York, NY, USA: JSTOR. http://plants.jstor.org/

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Links to Websites

Contributors

10/3/2014 Original text by:

Marianne Jennifer Datiles, Department of Botany-Smithsonian NMNH, Washington DC, USA

Pedro Acevedo-Rodríguez, Department of Botany-Smithsonian NMNH, Washington DC, USA

Distribution Maps