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The average number of centimetres the Saguaro cactus, the largest in the US, grows in 10 years. In its typical shape, the slow-growing cactus is seen as an icon of the American Southwest and is found only in the Sonoran Desert — southern Arizona, southeastern California, and Sonora, Mexico. Left to their own devices, they can reach heights of 15m. The Saguaro National Park in Arizona was established in 1933 specifically for their protection — but poaching has become a problem in recent years, mainly because of the high prices “rustlers” can get for the plants. Friends of Saguaro National Park says a 1.8m specimen can fetch about $60 (R700) per foot (30cm). Conservationists have now fitted microchips to roughly 1 000 particularly vulnerable specimens — that is adolescent plants in easily-accessed areas inside the park.

Officials say the chips can be used to identify stolen saguaros, but can’t track them. Therefore, the hope is that the devices will deter thieves.