Plantwatch: Relative of common weed can grow up to 30ft tall on Kilimanjaro

The common groundsel, a prevalent weed typically found in disturbed areas such as roadsides and waste grounds, usually grows to a modest height of about 40 centimeters (16 inches). However, its relatives found in the mountainous regions of East Africa exhibit remarkable adaptations that allow them to thrive in harsh environments. One notable species, Dendrosenecio kilimanjari, is endemic to Mount Kilimanjaro in Tanzania and can reach heights of up to 9 meters (30 feet). This extraordinary plant features a woody trunk that branches out in a unique candelabra-like shape, with large inflorescences adorning each branch, giving it an otherworldly appearance that contrasts sharply with its smaller relatives found at lower elevations.

These giant groundsels, including Dendrosenecio kilimanjari and other related species, have evolved specialized adaptations to survive in the extreme conditions of the upland habitats. The temperatures in these areas can plummet to as low as -20 degrees Celsius (-4 degrees Fahrenheit), accompanied by strong winds. To combat the cold, the plants are insulated by layers of dead leaves, which act as protective jackets. They also produce an antifreeze agent that helps to prevent ice formation within their tissues. Additionally, during the night, the leaves of these plants exhibit a behavior known as 'sleeping,' where they fold up to conserve heat. Given the scarcity of rainfall in their environment, these giant groundsels have developed the ability to store water within the pith of their stems, which is essential for their survival. Consequently, their adaptations not only allow them to endure extreme conditions but also result in a slow growth rate, reflecting the challenges they face in their austere habitat.