Around one in four people in the UK suffer from hayfever – and for those who also have asthma, pollen can exacerbate their symptoms. As such, the impact of pollen should be a key consideration for healthcare sites looking to expand their tree planting and landscaping. It is often said that the key to successful tree planting is the right tree, in the right place – if your species choice has a negative impact on your staff and patients, it’s probably the wrong tree in the wrong place!
Luckily, there are guidelines available for how to select the best species to avoid contributing to the summer suffering of people with hayfever, including this four-page guide from The Garden columnist Sally Nex.
The key issue is to create a balance: pollen-producing species are good for biodiversity and provide food for important pollinating insects such as bees, and eradicating pollen altogether isn’t necessarily the best choice for the wider environment. Many nectar-rich plants attractive to pollinators also have low allergy ratings, so it isn’t a case of ‘either/or’ when designing beautiful green spaces that can be enjoyed by humans and pollinating insects alike.
Pollen-producing species may be better suited further away from enclosed environments such as courtyards, as planting them in open air can help disperse the pollen. Pollen counts are also highest directly next to the tree in question; places that are within sight but slightly further away from paths and seating areas could be a good location for these species. Less allergenic species can then be planted closer to where people will be interacting with the trees directly.
Hazel, alder, birch and grasses are particular culprits when it comes to triggering allergies in hayfever and asthma sufferers. The OPALS scale can help you choose lower pollen-emitting plants – anything between a 0 and 5 on the scale should be suitable. Female plants are also less likely to produce pollen, so can be considered for planting nearer to paths, seating and courtyards. Trees with an OPALS rating below 5 include rowans, apples and crab apples, pears, hawthorn, plum, and spruce. Female yew and poplar are examples of low OPALS trees where the male specimen may trigger allergies.
If you are thinking of planting trees or developing the green spaces at your healthcare site this year, why not get in touch with the NHS Forest to see how we can help. From planting advice and assistance with projects, to the provision of trees themselves, we would love to hear from you.