42 foot giant redwood among tallest ever trees on RHS show ground Garden highlights diversity and biosecurity as paramount to our future     The Resilience Garden at RHS Chelsea Flower Show has unveiled a sensational variety of plants and trees including a giant redwood, monkey puzzle, prickly pear cactus, red yucca, and ginkgo.   The centre piece is a six metre tall grain silo, re-purposed as the designer’s studio with an oak floor and lined with a willow…