Thursday, 27 February 2014
Designing a Bee Friendly Garden
In an echo of the chicken versus egg debate, opinion is divided among scientists on which came first, bees or flowering plants. They are agreed, however, on the fact that by about one hundred million years ago, bees were dodging dinosaurs to pollinate flowering plants. Since then, bees and flowers have co-evolved. Flowers developed arresting colours, alluring fragrances and shapes that would easily accommodate bees. Bees evolved special body parts and body hair, becoming an unwitting third party in plants’ reproduction as they transported pollen stuck to their bodies from flower to flower. In rare cases the flower/pollinator evolution has been so specialised that only one insect can pollinate a plant. These tend to be plants whose evolution was not affected by glaciation, for example the large red flowers of the southern African Meneris tulbaghia is pollinated by a single butterfly species.
For millions of years the flower/bee relationship evolved without any outside interference but then we decided we could ‘improve’ flowers. We wanted larger petals, different colours and longer flowering periods. As plant nurseries became increasingly commercial, the competition to produce bigger, brighter and showier blooms became intense. In the process we began to disrupt the flower/bee relationship. We bred plants to encourage mutations of the flower shape that eliminated the pollen producing stamens. Often these mutations, such as double flowers, made the nectaries inaccessible. Nectar and pollen were off the menu for bees at these flowers.
The hunt for nectar and pollen became even more difficult as we began to fill our gardens with exotic plants introduced to the UK by intrepid Victorian plant hunters. Plants from all corners of the planet began to be grown in British gardens. Rhododendrons from the Himalayas, fuchsias from South America and gladioli from South Africa, among others, all became popular with British gardeners. Pollinated by the birds, insects or mammals of their native land, the flowers of these plants were often inaccessible to bees, or indeed any British native pollinators. Not all exotic plants are no-entry zones for bees, however, as we will see later.
Despite the best efforts of plant breeders and importers, there are still hundreds, if not thousands, of garden worthy plants that can provide a feast for bees and other pollinators. By following some simple principles, planting can be designed that is pleasing to the human eye and provides generous nectar and pollen sources for bees.
Good planting design starts with what is called ‘structural’ planting. This is the planting that will give the garden shape, height and definition, even in the depths of winter. Formal gardens often use evergreen shrubs and hedges such as box or yew, perhaps clipped to a geometric shape, to create this definition. In a bee friendly garden this structural planting is ideally British native trees or shrubs. Many of these are spring flowering and will create pollen and nectar sources early in the season, when bees can struggle to find food. Double flowered varieties should be avoided. A hedge of native shrubs starts flowering early in the season as the white froth of blackthorn appears. The beautiful white blackthorn blossom can appear as early as late February, often in a very cold period following a false spring. These cold snaps are known as ‘blackthorn winters’.
A native hedge will then continue flowering almost continuously until June when the native roses wind through the branches. It is not only a fabulous smorgasbord for pollinators but also an excellent habitat for other wildlife. The illustration shows a native hedge used as a garden boundary, it makes a good screen as well as providing lots of pollinator friendly plants.
While a native hedge will create a linear feature in the garden that can enclose space, create boundaries or screen unsightly features, a single specimen tree can be a focal point and introduce height into the garden. Again, a British native is a good choice to cater for pollinators. Trees such as the mountain rowan (Sorbus aucuparia), crab apple (Malus sylvestris) and wild cherry (Prunus avium) are great all-rounders. Rowans and crab apples have the added bonus of persistent fruit that will festoon the tree through winter as well as spring blossom, providing food for birds. Take advantage of the plant breeders’ work to choose a variety that contributes maximum interest to the garden; just steer clear of double flowers! A good crab apple is Malus x robusta ‘Red Sentinel’. Some non-native trees such as the Snowdrop Tree (Halesia carolina) are also good for bees.
Having ensured the garden has strong structural planting. The next step is to fill in the spaces that have been defined by the structure. This planting can be accomplished fairly easily with a selection of shrubs or a more complex planting of flowering herbaceous perennials in beds can be planned.
If shrubs are used, they should be chosen to provide a long succession of flowers throughout the season. Again, British natives are a good choice but, depending on flower shape, some exotic shrubs can also provide for pollinators. When planning infill planting it is worth creating a planting calendar to check you have covered as many months as possible.
Check mature heights and spreads when choosing shrubs. A common mistake is to plant shrubs too closely together so they do not have the space to grow into healthy plants. This does mean that planting can look a bit lean in the early years but this can be overcome by planting annuals such as poppies, cornflowers or clarkia. Alternatively, relatively fast-growing, sacrificial shrubs such as lavender can be inter-planted between the long-term planting and then removed as needed. Groundcover planting such as periwinkle or ivy can also soften the area around newly planted shrubs. Ivy is an excellent choice as the flowers continue to provide bee food late into the season.
Planting swathes of perennials to ‘froth’ through the structural planting can create a bit more drama and spectacle than shrubs. It does take more planning and maintenance, however, so it is not an approach to be taken lightly. That said, if you avoid the more high maintenance perennials such as delphiniums you can keep the work to a reasonable level.
Bees like to blitz a small area of flowers when collecting food. Large groups of the same perennial species planted together provide handy nectar bars that will soon attract large groups of bees as the news of a good food source spreads around the hive. Odd numbered groups of plants, 7, 9 and 11 are pleasing to the human eye. Plant in thin drifts of the same species that thread their way through the border. Ideally, place the later flowering perennials towards the front of the border. This means that as plants go over fresher blooms appear, concealing the dying flowers.
Bees do not see flowers as we do. They have compound eyes which means that objects appear pixillated; they do not see shapes as we see them. Bees seem to favour spherical flowers and this may be because their vision finds a sphere easy to distinguish. Their colour vision is also different from humans. We have three colour receptors that allow us to see blue, green and red. Bees also have three colour receptors but they see UV, blue and green. Many bee pollinated flowers have UV ‘landing-strip’ markings to guide bees to the nectaries. Besides their UV vision, bees can also detect the polarisation of light. Air molecules in the atmosphere scatter photons to create a pattern of polarised light arranged around the sun. This helps bees to navigate by the position of the sun even when the sky is cloudy. So plants with blue/purple flowers are visible, and attractive, to bees. Observation has revealed that bees also prefer yellow flowers and this may be because yellow is a pale colour that contrasts well with the green background of leaves. Many yellow flowers also have UV markings, invisible to us, but clear signposts to bees.
A well designed garden has open, flat areas as well as areas of planting. The open areas act as a respite to the profusion of planting. Ponds work well as open areas and will bring light and reflection into the garden. A well designed pond can be a great habitat for wildlife. The Pond Conservation Trust web-site, www.pondconservation.org.uk has lots of good advice on building ponds.
Lawns also create open space in the garden and British gardens are famous for their lush, rain-watered lawns. A traditional striped-green lawn is a mono-culture, however, and not a great source of bio-diversity. Bees prefer a flowering lawn, and many people agree with them. A flowering lawn does not have to be cut as regularly; indeed frequent cutting will stop the flowering. Lionel Smith of Reading University hit the headlines in 2013 when he planted a grass-free flowering lawn in a London public park. His blog makes interesting reading, blogs.reading.ac.uk/grass-free-lawns/rethinking-the-traditional-grass-lawn. Emorsgate Seeds, wildseed.co.uk, sell a Flowering Lawn Mixture that includes wildflowers that respond well to regular mowing. Of course, the ultimate flowering lawn is a meadow. If you have the space, and it probably does not need to be as large as you think, a meadow is a great food source for bees. Another opportunity for introducing more flowers into the garden is to install a green roof on your garden shed. They are an attractive alternative to traditional shed roofs and can be more effective insulators.
Plants that are good food sources are only half the story when it comes to a bee friendly garden. We have an imperfect understanding of how pesticides, and other garden chemicals, affect food crops and gardens in general. Do not use them if you want to avoid the risk of contaminating the garden ecosystem, either in the short or long-term.
So far we have discussed how to achieve a garden that is a haven for bees. It is worth remembering that bees evolved in a wild ecosystem of complex connections that link the smallest soil organism to the top predators. We are still learning how these connections work. While we can fine-tune the garden to suit bees, we should not lose sight of the bigger picture. A garden that supports wildlife and the local ecology in all its diversity benefits everyone, including the bees. The RHS and Wildlife Trusts web-site www.wildaboutgardens.org.uk has good advice about wildlife gardening in general. A garden that is beautiful for humans and a great habitat for wildlife are not incompatible. All it needs is a bit of planning.