Debbie Carroll and Mark Rendell of Step Change landscape design practice have carried out extensive research with 17 care homes, talking to people with dementia and their carers to determine the factors that encourage the residents to venture outside.
The project, entitled "Why don't we go into the garden?", aimed to explain why care home gardens - even highly landscaped ones - were not being more actively used by the residents, particularly those with dementia (around a third of the 800,000 people in the UK with dementia live in a care home).
In March, Step Change will publish a diagnostic tool and a handbook drawn from the research, to help both care homes and designers to find the interventions that will encourage residents into the garden.
According to Carroll, "amazing landscapes and fancy design" with modern planting can put residents off the garden. "People are very keen to have all the bells and whistles for dementia and care homes, to have contemporary planting. But actually we found for that generation it was the familiar planting that got more engagement," she explained.
"We've seen so many care gardens that meet the current guidance - one had close to £100,000 of charity money spent on the garden - but within a year the doors were locked." Yet some care homes have inexpensive gardens that are heavily used. Many of them feature plants such as lavender, rosemary, roses, sweet peas and tomatoes, which may trigger memories of home or childhood.
Unfamiliar contemporary plants can even cause residents to avoid the garden, Carroll suggested. "Grasses are very popular now, but at one point they were deemed a weed in a garden. There was one chap wouldn't walk down a path with a fluffy grass in a pot. They had to move it because he didn't like that plant. The only thing we could narrow it down to was that it was unfamiliar to him."
Ideally the space will feel like a domestic back garden, both in features and layout, said Carroll. No simple list exists of plants that are best for dementia patients - one may love lavender while another is a fan of succulents. The best design requires ongoing engagement with residents to find out their likes and dislikes. Step Change calls this "relationship-centred design".
In fact, this approach could better suit a maintenance contractor, said Carroll. "The most successful have been the contractor or garden designer who gets to know the residents, so that opens it up to any good contractor who chooses to use their wider communication skills. It's not one hit - you go in and build it up over time with the client."
Many people with dementia may only be in the home for 18 months. This high turnover means the garden design may need to adapt as new residents arrive. Some care homes in the study let residents bring plants from their homes in the hopes they will keep tending the plants in new surroundings.
"You may have found what works for Fred, but then he goes and Flossie comes in and can't abide that plant. Obviously there will be some structural plants needed but some will have to be slightly more temporary and ephemeral."
Finally, the garden's design needs to match the care home's ability to use it, Carroll pointed out. "Our findings identified that potentially we're designing beyond their organisational culture," she told Horticulture Week. "Health and safety fears, for example, can prevent the garden from being fully used. Garden designers can help support them to overcome those fears."