Science - May 14, 2011

Weeding out its own sort

The ragwort, a stubborn weed, digs its own grave within several years. The plant attracts bacteria and moulds which make the soil unsuitable for its future generations.

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The ragwort can bloom extensively on disused agriculture land and newly sown road shoulders. This pioneer plant is poisonous for livestock, in particular, horses. Although caretakers keep removing the plant, it continues to return. However, if left alone, the interactions between plant and soil will ensure that it disappears, says PhD graduate Tess van de Voorde.
Van de Voorde did research into this weed for four years at Wageningen University and the Dutch Institute for Ecology (NIOO-KNAW). Together with NIOO-researcher Martijn Bezemer, she researched into successions of the ragwort on former agriculture land in the Veluwe which has been disused for between two and 25 years. In addition, she also carried out greenhouse experiments to find out how weed and soil organisms affect each other.
The ragwort grows surprisingly less easily on soils where similar plants had been present, says Van de Voorde. 'This is 70 percent more difficult than growing on sterile soil.' Other grassland types such as the white clover, yarrow, vanilla grass and hairy tare also obstruct the growth of ragwort. As such, she says it is better not to pull out the Ligularias. However, it is wise to mow the plants to prevent seed production.
Tess van de Voorde defended her thesis on May 13 under Wim van der Putten, professor in Functional Biodiversity of the Laboratory of Nematology.

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