Currently Parham House head gardener at Parham, Brown will take over the reigns of West Dean Gardens in May.
Brown, who has been at Parham since 2010 and before that spent 10 years at RHS Wisley, is the first new head gardener at West Dean for 28 years.
Buckland and Wain were jointly named Custodian of the Year in the inaugural Horticulture Week Custodian Awards and are universally respected and admired.
As well as the garden, they are leaving behind the legacy of a trainee horticulturalist fund to help people at the beginning of their career gain the experience that will help them be tomorrow’s head gardeners.
Brown brought "rigour, excitement, fun and beauty" to Parham, according to owner Lady Emma Barnard, who said last week that "we are hugely indebted to him for his outstanding work over the years".
Director of estates, West Dean College of Arts and Conservation and West Dean Gardens Ian Graham said: "West Dean Gardens in West Sussex is one of the greatest restored gardens opened to the public in the UK. We are very pleased that Tom will be joining us in this prestigious role, which has become vacant for the first time in 28 years, and will lead the garden into an exciting future.
"Tom is already familiar with the gardens and has lectured for the college’s gardening short courses for a few years, including three courses coming up over the next few months."
Said Brown: "I have long admired the gardens and I'm enthusiastic about being part of its next chapter. I'm keen to develop and continue the unique artistic and horticultural collaboration - harmonising the gardens with the college and the wider West Dean Landscape."
West Dean Gardens is part of the Edward James Foundation, a charitable trust, also comprising West Dean College of Arts and Conservation, West Dean Estate and the West Dean Tapestry Studio.
There are 10 days left to enter this year's Custodian Awards, which recognise and reward the custodians of our parks, gardens, grounds and trees. Visit www.custodianawards.com for full details.