Pollen is not in itself harmful but in some people it can stimulate an immune reaction, during which powerful chemicals are released by the body that result in the characteristic symptoms of allergy, from sneezing and an itchy, runny nose (rhinitis) to experiencing tight chest, wheezing and coughing (asthma). The number of people with allergies is increasing, but the reasons are not fully understood. What is known is that the potential of different pollens from different plants to cause an allergic response varies widely.
The display for RHS Chelsea highlights how informed plant selection can create a highly ornamental but low allergen garden. Upper storey high allergen culprits like Silver Birch are replaced with low-allergen Japanese Maples; in the mid-storey, ornamental shrubs like Choisya and Citrus are selected over Lavender and Fremontodendron, and the beautiful spheres of low-allergen Allium are preferred over those of itch-inducing Globe Thistles (Echinops ritro). For ground cover, New Zealand Flax and Periwinkle take the place of ornamental grasses, which are known to have highly allergenic pollen.
Dr Tim Wreghitt, who is heading up the Royal College of Pathologists’ team said, ‘Everyone knows someone with an allergy. Based on a rooftop garden in central London, our exhibit aims to help gardeners and developers of garden spaces to pick the right plants to minimise allergies.’
Simon Wallis has been leading the Botanic Garden team responsible for growing on the display plants, provided by Scotsdales. He says, ‘The cold, wet weather has proved a real challenge, with some plants such as the Globe Thistles, the Asiatic lilies and Frementodendron 'California Glory' being reluctant to flower in time for the show. To redress the lack of sunshine, we have moved many of the plants under cover and artificial lights to try and coax them into flower. It's been a really good project to be involved with, and challenge to grow such a wide range of plants that all need to be in top shape for this weekend.'
The team ran a successful mock-up yesterday, and are feeling confident the plants will survive decamping to the RHS Chelsea Flower Show for the display build in the Environment Zone of the Grand Pavilion. Simon added, 'We have our fingers crossed for a gold medal, of course, but there is also rumour of a royal visit.'