Pick of the zingiest zinnias and how to grow them as cut flowers

'The popularity of zinnias grows with each successive season." So said the great Roy Hay, founder of Britain in Bloom and instigator of the National Gardens Scheme, back in 1937. What happened?

Well, there seems to have been a divergence of opinion - Gertrude Jekyll wrote that the zinnia was "another fine annual that has been much spoilt by its would-be improvers". But the "would-be improvers" carried on "improving" zinnias until in 1966 the RHS trial at Wisley had 75 varieties. There were 91 in the 2002 trial and this year 144 are growing in an impressive display at the RHS Garden at Wisley, marking the year of the zinnia.

Zinnias provide more different vibrant colours, on tall plants and short, than any other annual but enthusiasm for vivid colours has waxed and waned over the years. "Everyone loves a zinnia," proclaims the latest catalogue from Thompson& Morgan - well, not really, because it was often thought that they were tricky to grow. And that has been true, especially since the Sixties, as it was then that peat-based seed compost was introduced.