There are more than 63,000 different cultivated varieties on the RHS Dahlia Register. Dahlias originate in mountainous regions of Mexico and Central America. Known to the Aztecs as Acocotli and Cocoxochitl, the plant was renamed in the late 1700s by the Director of the Royal Botanic Garden of Madrid in honour of the Swedish botanist, Andreas Dahl. Dahlias grown from seed can display massive and unpredictable variety and following introduction to Europe, new forms were quickly developed. Dahlias became a popular flower in competitive flower shows. Dahlia trials were good way of establishing which new varieties held most promise. Wisley continues to be an important centre for trials and plants are collected for the Wisley herbarium as a permanent record.