The house and estate is the historic seat of the Boscawen family, Viscounts Falmouth. The original medieval house was ransacked in the 17th century during the English Civil War. The new house has the date 1652 carved in stone above the side gate. It was enlarged in the early 19th century to the designs of William Wilkins, the architect of the National Gallery in London.
Tregothnan is famous for its large private botanical garden and arboretum. Tregothnan is not open to the public, but guided visits to the garden may be arranged.
A tea plantation has recently been started on the grounds. Tregothnan was home to the first outdoor Camellias in the UK, around 1800. The first commercial tea was developed from Camellia sinensis, the "Chinese tea plant", in 2001. The first 'English tea' was then sold in November 2005 to Fortnum & Mason of Piccadilly. The Tregothnan Estate plans on marketing a brand-named tea housefranchise called Festival of Tea, to be opened as far afield as China.
Also a quantity of custom-made bee hives are situated in amongst Leptospermum "Manuka Bushes" producing Manuka honey with measurable methylglyoxal content. In 1872 the land holdings of Viscount Falmouth, of Mereworth Castle, Maidstone, Kent, were listed in the top ten land holdings in Cornwall, with an estate of 25,910 acres (10,490 ha), 3.41% of the total area of Cornwall.
^Tregothnan first grew Leptospermum in the botanical collection in the 1880s and may have helped introduce the genus to the UK in its Wardian Case, thought to be the only surviving example of a Wardian Case in the World. The extensive garden is usually open for a weekend in the spring and has become a major fundraising event for charities. "NZ beekeeper offers to test $13 tsp UK 'manuka honey'". The New Zealand Herald. NZPA. 22 May 2009. Retrieved 24 November 2011.