Glenwhan Gardens and Arboretum is the inspiration and creation of plantswoman Tessa Knott-Sinclair.
The garden began to take shape after Tessa and her first husband Bill Knott bought Glenwhan unseen in 1971 from Sir Charles Cooper before moving there from farming in Herefordshire in 1974 (Knott 2016). Glenwhan, in Gaelic means 'green valley'. Knott (2016) recounted how, at the time of their purchase, the 103 acres of bog, bracken and gorse were described as 'fit for afforestation'.
The land was initially let for pasture while the Knotts set about creating a family home by renovating a ruined former Grieve's house for Dunragit Estate that had last been lived in during the Second World War by James Kelly, the estate's last resident shepherd, along with wartime evacuees. This building appears on Ordnance Survey 1st Edition 6-inch maps (1843–1882) adjacent to a rectangular enclosure in an area of land called 'Dunragit Moor'. The same maps also depict the reservoir to the north of the gardens which supplied Dunragit Estate.
Tessa Knott-Sinclair had no formal horticultural training, but she had created a garden in Herefordshire and brought her plants with her. Initial forays into the garden involved 'taming' gorse-filled moorland, and growing vegetables on the fertile ground of an old lambing pen. Bill Knott liked trees, particularly hollies (ilex).
The idea of creating a garden at Glenwhan began to take shape in 1979, following visits to Tresco, Isles of Scilly, and to Logan Botanic Gardens, Stranraer (GDL00267). The gardens created by Lady Anne Palmer at Rosemoor, Devon, were also a significant inspiration. Tessa Knott-Sinclair worked largely from a blank canvas and the concept for the garden gradually evolved, growing outwards from the house.
Acting on advice from Chris Minchin of Game Conservancy, the Knotts planted a shelterbelt enclosing around 12 acres of land, consisting of hawthorn, sorbus, oak, hazel, sycamore, birch and pine. They retained native gorse plants retained as 'nannies' to shelter the young plants and latterly installed fencing to prevent damage by deer.
The idea of looking down on water arose from discussions with Chris Minchin (Game Conservancy) while sitting on 'Thinking Rock' - a natural rocky outcrop that overlooks the site with Luce Bay in the distance. As the Knotts began to work the ground, it became clear that a boggy area was being fed with water from a former reservoir above. This offered an abundant water source to realise their vision. They used a mechanical digger to excavate tonnes of soil, creating a watercourse that tumbles off the hillside before flowing into two small lochans.
The Lily Pond is the smaller of the two lochans. It was created a few years before Glenwhan Pond, the larger and deeper of the two ponds. At the centre of the Lily Pond is Kelly's Isle, named after James Kelly.
Planting of the garden began in the early 1980s with 100 hybrid rhododendrons and Knaphill azaleas. Dennis Woodland of Hilliers Nursery and Arboretum in Hampshire advised the Knotts to split the land into smaller named areas, to make walkways, to enrich the soil with farmyard manure and compost, and not to plant too close to the water which would block off the views.
As the shelterbelt grew and a microclimate developed, pathways were cut and species rhododendrons added, as well as many southern hemisphere plants and trees that the Knotts had seen growing in their native habitats while on worldwide tours with the International Dendrology Society. Mostly latterly, Tessa Knott-Sinclair has also introduced sculptures at focal points within the garden.
Glenwhan Gardens first opened to the public in the late 1980s for charity and averages 5,000–6,000 visitors per year (2022), with a tearoom, self-catering lodge and shepherd's hut added to further support work on the garden.
The garden has continued to evolve. By 2006, the Knotts had fenced off a further 17 acres to create a wilderness garden, with meandering walks amidst native moorland, wildflowers, ferns, mosses, and wildlife. In 2010, Tessa and Bill Knott's son Richard Knott, re-designed a vegetable plot at the centre of the garden into a productive formal potager. As the trees in the garden reached maturity, the 'Arboretum' was added to the name and, by 2013, the gardens were promoting a new 'tree trail'.
Glenwhan Gardens and Arboretum continues to exhibit a high degree of integrity and are in good condition. Following Bill Knott's death in 2018, Tessa Knott-Sinclair remains the driving force and inspiration for ongoing development. Expert support comes from her second husband, Ian Knott-Sinclair, formerly of the Royal Botanic Gardens Edinburgh, who collates plant and tree lists and labels the collections. Plans are underway (2023) to create a Chilean garden in the moorland garden by eradicating bracken before planting an area at the north-eastern corner of the Moorland Walk as a Chilean Arboretum, with plants such as Drimys.