Z Zinnias - colourful bedding plants which bloom in late spring in England. They are native to Mexico, and need dry warm conditions, so need to keep them indoors in plantpots in winter. "Easy to grow" according to BBC Gardening website. Not sure if I have ever seen any in gardens, but they look good in the photos. Some varieties look like mini-dahlias at first glance, but there are many other varied flower shapes.