Austroeupatorium inulaefolium (Kunth) R.M.King & H.Rob.

Code

AVQIN

Growth form

shrub

Biological cycle

perennial

Habitat

terrestrial

Austroeupatorium inulaefolium belongs to Dicotyledons, Asteraceae, Eupatorieae
There are 13 species of the genus Austroeupatorium; they are distributed mainly in South America and up to the north of Panama and Trinidad.
This species is very close taxonomically to Chromolaena odorata (species not present but potentially invasive for Reunion Island and already present in Mauritius, and Ageratina riparia (invasive species in undergrowth in Reunion).

Austroeupatorium inulaefolium is a perennial species. It multiplies by seeds. These are produced in very large numbers and spread by the wind (anemochory). Moreover, the seeds have a great longevity in the soil (about thirty years).

Austroeupatorium inulaefolium is distinguished from other species of the same genus by opposite leaves at the base of the plant often becoming alternate higher up, terminal inflorescences (capitula) of about 3 mm wide, bracts organized in involucre of 3 or 4 rows around each capitula, tubular florets (5mm long) of white-creme color arranged on a glabrous receptacle surrounded by bristles as long as the florets.

Austroeupatorium inulaefolium seems to prefer relatively shaded and humid environmental conditions. It would therefore have a smaller area of invasion than Chromolaena odorata and comparable to that of Ageratina riparia: disturbed undergrowth and edges of mesophilic and hygrophilic forests. In addition to natural environments, this species is also known as a weed of annual and perennial crops and could threaten all crops, including agroforestry.
A. inulaefolium is a plant of subtropical to tropical climate.

Global harmfulness

In its area of introduction, in South East Asia, this plant is used in the management of cultivated land as a cover crop, to improve soil fertility and prevent the development of weeds (such as Imperata cylindrica). Introduced at the beginning of the 20th century, it is now naturalized for decades in these regions. This shrubby plant has become a pioneer and regenerates spontaneously when a field is left fallow after harvest. The result is a dense monospecific plant cover that can reach more than 4 m in height. As local spread is important and uncontrollable, undergrowth and disturbed forest areas are invaded to the detriment of the original spontaneous vegetation.
Austroeupatorium inulaefolium is a very invasive plant in the Philippines, Indonesia, Sumatra, Sri Lanka and in a very large part of South East Asia. On the island of St. Helena, this plant is a growing problem and invades many disturbed, cultivated and pasture areas. In its Asian area of introduction, A. inulaefolium forms dense bushes in many perennial shrub and tree plantations (rubber, tea, palm...) but also in highland rice fields. In Saint Helene, all types of crops are affected, including pastures.

Risk of introduction in Reunion island

Voluntary introduction : Cover plant sector. This plant is indeed used in South-East Asia as a fallow, to avoid that other herbaceous and shrubby species develop there.

Unintentional introduction: The seeds, only 4 mm long, can be spread unintentionally by passengers or in the fur of animals, etc.

Viable forms of plant transport: seeds, rooted plant

The natural and cultivated environments favorable to the invasive development of Austroeupatorium inulaefolium are very widely represented in Reunion Island. Except for the West coast of Reunion Island which is subject to a too dry climate and the high altitude areas around the volcano or the Piton des Neiges, the other natural and cultivated environments are threatened. This corresponds to a large part of the island.

Potential impact on Reunion Island: The environmental impact of A. inulaefolium would probably be quite comparable to the current impact of Ageratina. riparia; by forming monospecific mats in the undergrowth of secondarized forests, the regeneration of the original vegetation is strongly disturbed. The impact of A. inulaefolium may be even more important because, being much larger than A. riparia, this plant eventually forms real shrubs (woody trunk) with very dense foliage. A. inulaefolium would be a serious problem in the majority of the crops in Reunion. This plant would cause an important nuisance in agroforestry zones.

Herbarium pictures ReCOLNAT : https://explore.recolnat.org/search/botanique/simplequery=Austroeupatorium%2520inulifolium