Carol Pickthall, from St Andrews, was given the award jointly by the National Trust for Scotland's School of Heritage Gardening and the Royal Botanic Garden Edinburgh (RBGE).
The Diploma in Botanic & Heritage Gardening offers both theory and practical skills to ensure graduates can perform effectively at a garden supervisory level.
School coordinator Colin Wren said: "Employers like the [National] Trust look to employ gardeners with a sound horticultural training – both practical and academic.
"While colleges offer excellent classroom training in the important scientific and artistic aspects of horticulture which underpin good practice, it has become increasingly difficult in recent years to find students who have gained sufficient hands-on experience and understanding of the skilled practical aspects of heritage gardening.
"Many of these traditional and modern skills can only be taught in any depth on a full-time practical course. The School of Heritage Gardening offers practical gardening skills to equip the future custodians of our heritage gardens."
Pickthall was a Trust volunteer at Falkland Palace before going to SRUC Elmwood College where she studied for a HNC. She completed the first year of Practical Heritage Gardening at Threave with distinction. She went on to Year Two of the HND in Horticulture with Plantsmanship course at RBGE, where she also achieved a distinction.
She completed her second practical year in heritage gardening at Crathes Castle garden, where she updated the champion tree records. After her travels, Pickthall plans to work in horticultural therapy or to study further for a degree.
The four-year heritage gardening diploma:
Year 1: HNC in Horticulture with RGBE or other college
Year 2: Scottish Heritage Gardening Certificate in Practical Heritage Gardening at SHG Threave
Year 3: Year 2 of the RBGE HND in Horticulture with Plantsmanship at RGBE or Scottish Agriculture College SRUC
Year 4: SHG Diploma in Heritage Gardening, 2nd practical year in heritage gardening with garden management linked assignment, at NTS garden or another approved heritage garden.