The Genus Cortaderia
Cortaderia Selloana is probably the best-known species in the Atlantic Arc. According to the Spanish Catalog of Invasive Exotic Species, the first reference to the presence of this species escaped from cultivation in Spain is from 1969, corresponding to a sheet from Enrique Loriente's herbarium, currently deposited in the Royal Botanical Garden of Madrid, with herbalized material in Liencres (Cantabria).
In its native area, South America, it is found in areas with a temperate and oceanic climate, with mild winters, such as the Argentine pampas and the south-east of Uruguay. There it is part of herbaceous communities called "pajonales", although it is also part of riverine communities. On the Chilean coast with a Mediterranean climate it grows in dune depressions and in bush communities with the presence of brackish water.
How did it arrive?
It is an ornamental species
It is a plant deliberately introduced in Europe and Spain as an ornamental due to its showy inflorescences (“dusters”). It has also been used, for example, as a visual barrier or windbreak along roads and in industrial or commercial landscapes, as well as to control erosion, which has caused its escape and naturalization in various parts of the world.
Its sale is prohibited
In Europe it was introduced for the first time as an ornamental species between 1775 and 1862, in the United Kingdom. In 1874 it began to be produced commercially in the United States and Europe, and since then its use in gardening has become popular throughout the world. In fact, despite the prohibition that its inclusion in the Spanish Catalog of Invasive Exotic Species entails, it is still possible to find it in certain stores...
Disperses over long distances
Plants established in parks and gardens or naturalized next to communication routes are sources of natural dispersal through seed production. These are very light, produced by thousands or thousands, and are primarily transported by the wind (distances of up to 25 km have been recorded), although they can also be transported by water, by animals, by vehicles, machinery, clothing and footwear, etc.
Why does it become invasive?
Species of the Cortaderia genus have a great capacity to invasive and transform the environment, affecting both protected spaces and habitats of community interest in coastal areas and river systems, as well as areas altered by humans. Specifically, the species C.selloana has become a very important problem in the Atlantic Arc. The main reason for its success lies in its low habitat requirements, vigorous growth and prolific production of wind-dispersed seeds. Seeds can germinate in a wide variety of environmental conditions, although the germination rate is higher in the shade, in sandy soils and with high water availability, but they can germinate in full sun, in soils with low sand content and little water. .
High resistance and adaptability
Adult plants resist frost, high summer temperatures, direct sunlight, moderate drought and exposure to winds from the sea. Under water stress conditions, they maximize water intake by increasing root biomass and reducing aerial biomass.
Sexual and vegetative reproduction
It has very vigorous growth and prolific seed production, mainly anemochorous dispersion. It can reproduce vegetatively by root fragments with the capacity for regrowth.
In the Spanish Catalog of Invasive Exotic Species all Cortaderia species are contemplated and, in compliance with the aforementioned regulations, a “Strategy for management, control and possible applicable eradication of the Pampa duster (Cortaderia selloana) and other species of Cortaderia”. In Europe, C.selloana has also been listed as invasive in Portugal, Italy and France and is considered one of the “100 worst invasive species” in the DAISIE database. However, only C. jubata is included in the List of Exotic Species of Concern for the European Union.
Species description
It is a perennial grass plant that forms robust clumps up to 3 or 4 meters high, made up of long, narrow, ribbon-like leaves, flat and glaucous, with a 'V' cross section and bluish-green in color, with curly ends. In addition, they are leathery, with serrated edges, rough to the touch and covered by silica crystals, which makes them sharp and unpalatable to herbivores.
Both pollination and seed dispersal occur by wind. Each flower can produce thousands of seeds per reproductive cycle. The seeds produced by female plants are covered with long hairs that make them ideal for aerial dispersal over long distances by wind; In addition, these hairs allow the seeds to adhere to rough surfaces, also facilitating their transport by other means. Individuals with hermaphrodite flowers do not have the capacity to produce hairy seeds, which reduces their ability to disperse through the wind (anemocory).
Its flowers are arranged in spikelets of around 20 millimeters in length. Each spikelet has between four and six flowers. The feathery-looking floral plumes (panicles) are silvery or slightly pink in color and are more than 30 centimeters long. There are female plants and hermaphrodite plants. Hermaphrodites functionally act as pollen donors, and their seed production is much lower. In addition to propagation by seeds, the feather duster has the capacity to reproduce asexually by fragmenting the strain from root fragments with the capacity to take root.
The annual cycle of Cortaderia selloana has six phenological phases. In summer is when it blooms, being more recognizable. It produces seeds in autumn, when it is potentially most dangerous for the environment.
During its first phase of establishment, the feather duster has little ability to compete with other species of flora. However, once maturity is reached, the plant has a high growth rate and space occupation, which is key in the colonization and invasion process. The arrangement of adult specimens forming clumps makes it difficult (even preventing) the settlement of native species, both herbaceous and woody.
