Common Name:

General Information

Chromolaena odorata often starts its life as a perennial plant with more or less woody stems that die down at the end of the growing season. It eventually becomes more shrub-like, producing long, rambling stems that can be 7 metres or more long; forming tangled thickets of growth up to 3 metres high in the open and 7 metres or more in the forest[, , ].
The tree is harvested from the wild as a local source of medicines. Often grown as an ornamental, it also has potential as a pioneer species in reforestation projects.

Known Hazards

When applied as a green manure in rice paddies, compounds in the plant may kill fish[].

Botanical References

Range

S. America - Argentina, Paraguay, Brazil, Bolivia, Peru, Ecuador, Colombia, Venezula, Guyanas; C. America - Panama to Mexico; Caribbean to SE N.Americ

Habitat

An opportunistic plant that invades clearings and river flats in the rainforest. It appears early in the successional stage, rapidly establishing dense thickets and then gradually disappearing as the rainforest canopy closes in[].

Properties

Weed Potential	Yes
Edibility Rating
Medicinal Rating
Other Uses Rating
Habit	Shrub
Height	3.00 m
Growth Rate	Fast
Cultivation Status	Ornamental, Wild

Cultivation Details

A plant of the warm and humid tropics and subtropics, where it is found at elevations up to 1,000 metres. It grows best in areas where annual daytime temperatures are within the range 20 - 35°c, but can tolerate 16 - 38°c[]. It can be killed by temperatures of -1°c or lower[]. It prefers a mean annual rainfall in the range 2,000 - 4,000mm, but tolerates 1,500 - 5,000mm[].
Requires a sunny position[]. Succeeds in many soil types, but prefers well-drained soils[]. Prefers a pH in the range 5 - 6.5, tolerating 4 - 7.5[].
Commonly grown as an ornamental, in recent decades the plant has become a serious pest in the humid tropics of South East Asia, Africa and the Pacific Islands. It has small, wind-dispersed seeds that can also cling to hair, clothing and shoes. It spreads rapidly in lands used for forestry, pasture and plantation crops such as rubber, coffee, coconut, cocoa and cashew[]. The leaves and petioles have glandular dots emitting a strong pungent smell when crushed - phenols and alkaloids in the plant, in particular in the leaves, have an allelopathic effect, inhibiting the germination of its own seeds and seedling development of other plants[, ]. The plant forms dense stands in disturbed land, preventing the establishment of other species, both due to competition and allelopathic effects[].

Edible Uses

The leaves have occasionally been used as an aromatic addition to soups[].

Medicinal

The leaves are said to be antibiotic, antimalarial and febrifuge[]. An infusion of the leaves is taken to cleanse the blood[].
The young leaves are crushed, and the resulting liquid can be used to treat skin wounds[].The leaves are used to treat eye pains[].

The stem is used in an emollient mix to use while extracting splinters[]. The stems and branches are crushed and combined with the wood-pulp of Cecropia obtusa and a seed of Theobroma cacao, this is then kneaded in Carapa oil, and locally applied in a plaster[].

The seed contains alkaloids[].
The leaves contain cerylic alcohol, sisterol, isosakuranetine and odoratine[].
An essential oil in the plant contains sesquiterpenic acid, eupatol and anisic acid[]. It has been shown to have an anti-bacterial activity on Staphylococcus aureus and Escherichia coli[].
The whole plant contains triterpenic alcohols[].

Agroforestry Uses:

The plant flourishes in disturbed habitats, particularly in areas of slash and burn agriculture[]. The shoots bend over due to their increasing weight - consequently apical dominance is broken and new shoots develop. The bent shoots die and form a thick, sagging mat in the vegetation which absorbs the light of plants in the understorey and hinders their vertical development by mechanical pressure. It is thus considered to be a noxious weed in pasture, where it suppresses the growth of grasses. However, this also makes it an excellent pioneer species in the succession from open space to forest. Its lifetime depends on the presence of woody species in the vegetation - it cannot regenerate in shady places and so tree growth eventually shades it out[]. It can be used as a pioneer species when re-establishing woodland, but it should only be used within its native range for this purpose because of its propensity to invade non-native habitats[].
The plant has become a serious pest in the humid tropics of South East Asia, Africa and Pacific Islands, where it spreads rapidly in lands used for forestry, pasture and plantation crops such as rubber, coffee, coconut, cocoa and cashew. Its positive aspects are that the plants create a lot of humus and raise pH levels on very acid soils[].
Although, under certain conditions, the plant can be one of the most noxious weeds in agriculture, it is used in Cambodia as a green manure in the production of lowland rice, cassava and black pepper, whilst in Nigeria its use as mulch in yam, cassava and coffee is subject of research[].
The plant is recommended for the control of Imperata cylindrica[].
In both Asia and Africa a natural fallow of the plant is gradually becoming more common in semi-permanent food crop production, and many small farmers in countries such as Indonesia and Laos consider it a most useful fallow crop[].
The plant is known to harbour parasites and pathogens injurious to crops, including grasshoppers (Zonocerus variegatus); weevils (Aphis spp.); nematodes (Scutellonema bradys); and microorganisms (Cercospora spp. causing leaf spot disease, Fusarium oxysporum and Pseudomonas solanacearum). However, they rarely do serious harm[].

Other Uses

The leaves are reported to be useful in controlling the weevil Cylas formicarius and the butterfly Phtorimae operculella in sweet potato, the nematode Heterodera marioni in black pepper, as well as nematodes in sugar cane and tomato[]. Mulching black pepper with this plant reduced the nematode infestation (Heterodera marioni) and secondary infection of Pythium spp. All the pepper vines in the untreated plots died within 3 years, but nearly all survived in the mulched plots[].

Propagation

Seed - it requires light to germinate and is best sown very near the surface, but it may still emerge when buried up to 3cm deep[]. Emergence takes 4 - 12 days[]. During the first 3 months of growth the seedlings stay rather small and mainly form leaves. Later, the length and biomass of the stem increase rapidly. Before growing downwards, the primary root forms a small, horizontal part, from which many secondary roots develop. During further growth it swells progressively and serves as a storage organ from which new shoots may sprout[]
Viability of fresh seed ranges from 33 - 66%. A small proportion of the seed will germinate when freshly harvested, but most remains dormant - after 2 years up to 40% of the seed will still germinate[].
Cuttings - the nodes of branches readily root when in contact with moist soil[].
Root cuttings

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