The first bumblebee queens of spring are such a welcome sight. And though some insects, like aphids and vine weevil, give their fellows a bad name, an RHS report published last summer showed the vast majority of invertebrates are either “goodies” or don’t affect us at all.
In a four-year study, researchers examined the role of plants in the garden ecosystem and have now published a second paper, Plants For Bugs, on their findings.
Using 36 trial beds in RHS gardens, the scientists looked at how resident wildlife used every part of plants, assessed whether the origin of our different plants mattered, and the importance of planting density.
Researchers recorded the many thousands of invertebrates in the trial plots and divided them into four groups: herbivores, like aphids; carnivores, like hoverfly larvae; omnivores, such as ants; and the detritivores, or recyclers of dead vegetation, like worms. Of the 23,000 specimens identified, 18 per cent were herbivores, 18% carnivores and 3%
omnivores. The other 61% were detritivores.
A healthy, functioning ecosystem needs all these types of creatures, so gardeners need to provide the right food and shelter for them. A good supply of nectar, from spring to autumn, is obviously vital for pollinators. This means we need flowering plants from pulmonaria and crocuses in early spring right through to autumn asters.
Despite opinions to the contrary, native flower species did best, as bees and moths found our near native species from northern Europe 10% less attractive. Exotics from the southern hemisphere extend the flowering season. And though they were 20% less appealing, they kept supplying pollinators with a steady source of invaluable nectar.
Leaves make equally useful food for other invertebrates, like greenfly. In turn, these herbivores provide an essential meal for carnivorous beetles and ladybirds.
So we should tolerate aphids if we’re to enjoy seeing lacewing and damselfly. But don’t panic, these herbivores will not proliferate unchecked: I rarely see an aphid on my roses because my army of flying predators keeps them firmly under control.
Suitable shelter and living space also matters and this entails laying on different habitats for them all. Close planting not only encourages more pollinators to a bed, but it also offers a safe haven for thousands of beetles, spiders and centipedes, not
to mention bigger players such as hedgehogs and toads.
All heights of grass play a part. Neat lawns are ideal for many small flies and roving spiders, while a long, more tangly spot not only offers shelter but it’s an ideal spot for orb web spiders to weave their webs.
Mulches are good stamping grounds for rove beetles, and make ideal habitats for detritivores, those vital recyclers that break down dead vegetation and return nutrients to the soil. Fungi work on woody material before allowing bacteria and lots of different soil organisms to complete the task. Different species of worms munch through softer vegetation and cart it underground, improving soil structure and distributing nutrients.
This recycling happens throughout the garden, whenever a leaf or plant dies and isn’t instantly tidied away by the diligent gardener. Some dead vegetation should definitely be removed if it’s going to offer sanctuary for some unwelcome herbivores, like cabbage-infesting grey fly. But fallen leaves in a border are probably worth leaving on bare soil.
The compost heap is undoubtedly the garden’s main recycling factory. Provided it’s not diseased, dead plant material should all be fare for the compost heap where millions of small creatures, such as springtails, fungi and soil organisms convert it into fertile soil, ready to enrich the ground.
This whole living community can only thrive if it’s not damaged or killed by pesticides and herbicides.
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