The aisle at Westminster Abbey is being transformed into an "avenue of trees" up to 25ft tall for the royal wedding.
Six field maples and two hornbeams will flank the route to the altar as part of Kate Middleton's floral plans.
Almost 30,000 flowers, most taken from Windsor Great Park's Valley Gardens in Surrey, will adorn the abbey on Friday, including azaleas and blossoms.
Wedding florists say the choice of white, green and cream foliage reflects the bride's English country style.
Large containers of green cuttings have already started arriving at the abbey in central London from the royal estates of Sandringham and Windsor.
Artistic director of flowers, Shane Connolly, said: "The theme is that everything is from the estates, that everything is English, that everything is seasonal, and all along Catherine has asked that it's just all neutral colour-wise.
"The aim is the abbey looks unpretentious and simple and natural and that it reflects the fact that Catherine is a country girl at heart and that the couple are the best of British."
He said the language of flowers, according to a Victorian coding system, can convey secret messages.
"The trees are field maples, which is a very English native tree and the field maples symbolise reserve and humility," Mr Connolly said.
"The hornbeams represent a resilience in the language of flowers so we hope that the couple's life is full of resilience and full of strong love."
It is traditional for a royal bride's bouquet to contain a sprig of myrtle from the bush grown from the original myrtle in Queen Victoria's wedding bouquet.
Royal brides also send their bouquet back to the abbey to be put on the Grave of the Unknown Warrior - a poignant memorial to the dead of World War I.