The world’s oldest potted plant is the Eastern Cape giant cycad (Encephalartos altensteinii) in London’s Kew gardens. The plant, which now weighs over a ton and is nearly 13 ft tall, arrived to Kew in 1775. – WTF Fun Facts
Source: https://www.kew.org/read-and-watch/oldest-pot-plant-in-world-eastern-cape-giant-cycad