Dr Mark Spencer looks at the best plants for biodiversity
On occasion, I hear garden design professionals express the view that British wild plants are not garden-worthy. It is true that compared to Continental Europe, we have relatively few wild plant species, and that some are unlikely to be considered adornments; only we botanists are likely to love the extremely rare starved wood sedge (Carex depauperata).
Sadly, most of our once rich and beautiful lowland habitats are now destroyed or very heavily damaged. It is therefore not easy for designers to seek inspiration in our own plant communities; most are now drab near-monocultures. Thankfully, inspiration can be sought in those precious surviving patches of landscape managed by organisations such as the National Trust or the Wildlife Trusts. Some of my own personal favourites are Magdalen College Meadow, Oxford, bursting with snake’s-head fritillaries (Fritillaria meleagris); The Lizard Peninsula in Cornwall, which has some of the greatest diversity of wild plants in Great Britain and some of the most beautiful plant communities; while in spring, the gorgeous ash-dominated woods of Dovedale in the Derbyshire Dales will readily inspire.
For larger projects, especially those in, or near, environmentally sensitive areas (such as National Parks), a Phase One Habitat Survey is advisable, and may be obligatory under some circumstances. These should be undertaken by an experienced botanist or ecologist. Whilst this may feel like an onerous task, most botanists and ecologists are often very willing to provide additional guidance regarding the suitability of the proposed works and planting scheme.
This guidance can often lead to improvements that enhance future maintenance schedules as well as provide benefits for wildlife. It is important to remember that knowledge of what is already growing in a location may provide valuable insight into what will succeed in the future.
Closer to home
Garden owners often hanker for the novel. Over the centuries, this has driven us to search further afield – first the Mediterranean, then North America and South Africa, and finally temperate South America, Asia and Australasia. This passion continues unabated, yet in our excitement, we have come to overlook those European plants that our ancestors cultivated and valued. These ‘near natives’ are often more in-tune with our insect communities than plants from outside Europe.
Members of the daisy family are often considered valuable food sources for a wide range of insects. However, this may not always be the case. The sunflowers (Helianthus) of North America have close-knit relationships with specific pollinating bees, which may visit these plants and only a few other species; these are relations that don’t endure here. Planting European ‘near-natives’ may reduce this incompatibility, as most of our pollinators originated from Europe after the last Ice Age.
In Britain and Ireland, there are two native species of knapweed (Centaurea nigra and C. scabiosa) as well as several long-established non-natives; the cornflower (C. cyanus) being the most well-known. In Europe and adjacent regions, the knapweeds are a large and diverse group of plants that come in many colours and growth forms that suit a variety of garden schemes; notable ‘near-native’ species include C. dealbata, C. gymnocarpa and C. macrocephala.
I am often asked “What should I plant?” and “What would you plant?” Deciding this can often be informed by local knowledge. The Botanical Society of Britain and Ireland (BSBI) has a national network of ‘vice-county recorders’ who are experts in the wild plants within their areas. VC Recorders are approachable, but please remember the network is primarily voluntary.
Being a plantsman, I would generally like to grow most things, including starved wood sedge, but the following are some of my favourites. Hemp-agrimony (Eupatorium cannabinum) is a handsome, late-season plant and an excellent food plant for pollinators. Alongside hemp-agrimony, greater knapweed (Centaurea scabiosa) is a fine later-season plant that also has beautiful seedheads in winter. Gardeners often don’t realise that the popular round-headed leek (Allium sphaerocephalon) is a British native, albeit a very rare one. Like Centaurea, the genus Allium has many excellent ‘near-natives’.
Another deeply glamorous ‘near-native’ is willow gentian (Gentiana asclepiadea) and given the right conditions this will gradually spread through the garden. We should never eschew the common. The common and beautiful yellow flag (Iris pseudacorus) is often planted by ponds. It can become overly vigorous but planting it in moist soil can subdue that tendency. The native bluebell (Hyacinthoides nonscripta) is one of the most beautiful plants on the planet. Other ‘humble’ natives such as honeysuckle (Lonicera periclymenum) are also important garden plants with several named cultivars.
Fashion is a fickle thing and, sadly, most gardeners now wince when the words ‘heather’ or ‘heath’ are mentioned, but several European species such as the Cornish heath (Erica vagans) are versatile, drought-resistant plants that are much beloved by pollinators. This plant is one of the glories of The Lizard and looks stunning there in the company of black bog rush (Schoenus nigricans), and it would associate nicely in the garden with my last choice, tufted hairgrass (Deschampsia cespitosa).
I would plant this in preference to the now overused New Zealand wind grass (Anemanthele lessoniana) or Mexican feather grass (Nassella tenuissima), both of which I fear may become invasive.