How can we help stop the decline of bees?
- Credit: Nigel Sutton
Ruth Pavey looks at how wildlife friendly gardening could benefit pollinating insects.
The Royal Horticultural Society’s research project, “Plants for Bugs” gives a useful steer to gardeners who want to help stop the decline of pollinating insects such as bees.
It covers more than just pollination, but that is the subject of the first results to be released which appeared in RHS publications The Garden and The Plantsman.
For sometime there has been enthusiasm for wildlife friendly gardening, with a loose understanding that the way forward is through native plants, single rather than double flowers, longish grass, rotting logs, nettles and a touch of disorder.
To many gardeners, this is not a pleasing formula, not least the part about native plants.
Compared with other parts of the world, our native flora is pitifully limited, which may be why we have been such avid collectors from abroad. But in some conservationist quarters, where puritanism is not unknown, the superior value of native plants has been upheld.
According to the RHS, around 70 percent of the plants in an average garden are non-native. With more industrial farming, gardens are recognized as a vital resource for pollinators. So if it is true that our pollinators only like the flowers that they, as it were, grew up with, and 70 percent of what we are planting is not to their taste, there is a clear mismatch. But is it true?
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The field study for “Plants for Bugs” was spread over four consecutive years, starting in 2010. There were two sets of eighteen 3m x 3m beds, one in the RHS garden at Wisley, one in a nearby research field. The aim was “to test whether the geographical origin (nativeness) of garden plants affects the abundance and diversity of invertebrates they support”. Using a range of plants including bulbs, perennials, shrubs, grasses, with no double-flowered cultivars and no pesticides, the beds were planted in threes, with
1) UK natives
2) Northern Hemisphere ex UK (near-natives)
3) Southern Hemisphere (exotics).
Researchers observed the aerial subjects, those crucial to pollination, at six week intervals. They recorded “good” numbers of long and short-tongued bumblebees, honeybees, solitary bees, hoverflies, but “low” numbers of butterflies. The value of doing the research over four years is suggested by the variation from year to year, with 2600 sightings recorded in 2011, but only 1400 in 2013.
The results showed, unsurprisingly, that where there were flowers, there were pollinators. Overall, these were more numerous on the native and near-native beds than on the exotic. But there was seasonal variation in that the exotic beds came into their own in late summer, with flowers like dahlia. But the essential message is, native plants on their own do not seem to attract as many pollinators as do a mixture of native, near-native and exotic. So think about providing a succession of helpful plants rather than worrying about where they came from.
The RHS has online lists of plants useful for pollinators (rhs.org/perfectforpollinators). Here are just a few … common ivy, winter honeysuckle, pulmonaria, mahonia, rosemary, crocus (good because they flower when flowers are scarce) followed in spring and summer by allium, borage, thyme, nasturtium, buddleia, nicotiana, lavender, marigold, marjoram, fennel, ox-eye daisy, knapweed. Then later, verbena bonariensis, ice plant, dahlia, chrysanthemum. Trees are very good too, especially fruit trees, and pollinators are good for fruit trees. Which is, after all, why we are bothered about their decline in the first place.