Gardeners' World comes from the RHS Malvern Spring Festival. Adam Frost and Arit Anderson reveal the highlights of the show gardens and this year's must-have flowers and plants on display in the Floral Marquee.We meet a pond plant specialist in Lincolnshire who is exhibiting at the festival for the first time, and in the run-up to the show, we visit a family nursery with a passion for the jewel-like auricula.Carol Klein celebrates the range of blossom on show at this time of year at Batsford Arboretum in the Cotswolds, and in Worcestershire Nick Bailey revels in one of the stars of the early summer garden – the peony.