Sorry. It's not Cannabis sativa.
The oldest pot plant is actually the Eastern Cape giant cycad, also known as Encephalartos altensteinii.
Like all cycads, this is a prehistoric plant.
Encephalartos is derived from the Greek en (within), kephali (head) and artos (bread) because the pith of the plant can be used to make a bread-like food. The species name altensteinii is a tribute to Baron von Stein zum Altenstein (1770-1840), a Prussian statesman at the court of King Fredrick William III.
The following photos of male and female cones are from Dave's Garden.
The. E. altensteinii is dioecious meaning it produces male and female cones on separate plants. In order to propagate it by seeds one must have a male and female plant. Both plants should cone at the same time to increase the chance of pollination. It takes about 7 to 10 years before the first cone appears.
The leaflets are stiff and green and have marginal spines. It feels like plastic if you touch it.
The IUCN has listed it as a vulnerable species since 1998 and it is listed on Appendix I of the CITES Appendices.
The most famous specimen of this plant can be found in the Royal Botanic Gardens, Kew. The specimen at Kew was collected in the Eastern Cape region of South Africa in 1773 by plant hunter Francis Masson. It has produced a cone only once at Kew.
Of course you guessed it right. The Kew E. altensteinii is the oldest pot plant in the world.
Isn't it just amazing? Over 200 years old and appreciated by so many generations of Kew visitors.
I too have my own E. altensteinii but my specimen is much, much younger than the one at Kew. Just two years old, with proper care it will definitely outlive my generation. I wonder how many generations will get to appreciate my plant?
The oldest pot plant definitely gives a different kind of high.