It's week six of The Great British Bake Off and just seven bakers remain. This week, for the very first time on Bake Off, it's Botanical Week.There are three challenges inspired by nature. The bakers can reach for anything that grows to give their bakes maximum botanical taste.The bakers start with a signature challenge with a twist, that demands sharp citrus flavours and perfect peaks. Hidden under the gingham cloth is a leafy technical challenge set by Mr Hollywood. And finally, the botanical showstopper is the biggest challenge of the series so far - not one, not two, but three tiers of elaborately decorated cake.Paul and Mary are looking for beautifully flavoured sponges and to be wowed by stunning floral designs. Three challenges, three chances to win star baker, three chances to avoid leaving the tent.