The famous garden's blooms were placed in every class they entered gaining ten first places, seven seconds, and five thirds in rhododendron classes; three firsts, two seconds, one third and the Williams Challenge Trophy for the best bloom in the show in the camellia classes.
Trewithen's Head Gardener, Gary Long, said: "We're absolutely delighted and a little surprised because the competition was fierce."
Gary explained that last summer's wet June followed by the cold winter provided perfect conditions for rhododendrons to set their flower buds. This season's display at Trewithen has been the best ever, but the same has been true across the country producing some extraordinary specimens at the show.
To prepare the entries, the Trewithen team spent two days carefully selecting and picking specimens before setting off from the garden, based near Probus just outside Truro, at 3am on Saturday. They arrived at Rosemoor at 6am and arranged their blooms in time for the judging to start at 10am. All the show's judges were experts in their field with international reputations.
Gary said: "Rhododendrons really are flavour of the month at the moment, we've had such a fabulous season that at Trewithen we've made 2011 the Year of the Rhododendron. Rhododendrons are on the front cover of this year's RHS Chelsea flower show catalogue and they are Plant of the Week and the focus of this week's edition of Horticulture Week."
Trewithen Garden is open daily from 10am to 4.30pm. Full details of the garden's attractions, opening times and entry prices are available on www.trewithengardens.co.uk.