This plants for bugs blog is partly a review of the RHS trial, but also a look at what is a native species plant.
And whether you can have a garden that suits bugs and humans, which sometimes seems to get forgotten in all the talk of wildlife gardens…
What is a Garden Bug?
In the sense of this trial, it includes all garden invertebrates. That is, creatures without a spine (backbone). However, as about 96% of all known animals are invertebrates, that’s not as helpful as you may first think.
But it is, in so far as it excludes garden wildlife which are vertebrates. These would be the mammals such as foxes, hedgehogs, rabbits, deer, badgers. The amphibians – toads, frogs, newts – and the fish in our garden ponds. And of course all the garden birds: sparrows, blackbirds, robins and so on.
So bees, earthworms, dragonflies and spiders are all invertebrates. (See ‘Invertebrates’ in our gardening glossary for more information). The study found over 300 species of bugs during the four years of the trial, including 16 species of butterfly, 47 species of ground beetle and 50 species of spider.
Plants for Bugs – the RHS Trial
This research trial was carried out at RHS Wisley garden in Surrey 2009 – 2013. It was set up to establish whether the commonly held belief ‘native plant species are best for wildlife’ can be validated by scientific research.
The aim was to mimic a garden setting. Research (notably led by Sheffield University) has shown that city gardens are critical in the creating and maintain biodiversity.
Thirty-six 3m square beds were created to represent garden borders. The beds were divided into categories relating to the origins of the plants: –
These were then each planted with 14 differing plant species including herbaceous perennials, bulbs, shrubs, climbers and grasses, ferns.
Cultivation was by hand weeding and watering; no pesticides were used. The invertebrates were recorded using various methods. Including what is effectively a giant vacuum cleaner that sucked up over 22,500 bugs over the 4 years!
Report papers have been published with the findings since then. The first looked at pollinating insects which feed on flowering plants (plants for pollinators). The recent report (August 2017) reviews the results relating to bugs that eat plants and other invertebrates.
Plants for Bugs – the Categories of Plants used
As we grow such a diverse range of plant species in our gardens these days, does it matter if they’re a UK native species? And what is a UK or British native species plant anyway?
UK native species and British native species are not exactly the same, geographically speaking. British generally is taken to mean the mainland of the British Isles, whereas UK encompasses Ireland and all the islands. The strict definition for native is of a plant species which originated here or made its way here naturally, ie without human intervention, before the UK was separated from the mainland, about 10,000 years ago.
A naturalised species is a non-native plant which has become established in the wild in sufficient numbers to be a self-supporting colony.
There can be some confusion over whether a plant is native or naturalised when it has been in a region for a long time. Especially if records of its actual introduction are non-existent. Scientific methods such as DNA clarification can be used to back track a plant’s origin. For more of these plant related definitions have a look at Plews Gardening Glossary.
Native or Non-Native – Which are the Best Plants for Bugs?
As you’d expect, native plant species overall are best for native bugs. However, planting mainly, but not purely, native species works too. Near natives, ie other plants from the Northern hemisphere, are similar enough to be almost as effective. And of course the likelihood is that you would have some of these in a British garden anyway.
And as for those other non-native plants from the Southern hemisphere, they have their uses too. They extend the flowering season into the autumn beyond that which natives would flower. Thus providing a direct food source for the pollinating insects and the plant eating, herbivorous, invertebrates.
Briefly, native plants supported about 10% more invertebrates than near-natives and 20% more than exotics. The full list of plants used in the trials by the RHS can be found here. Some of those included may surprise you and be new to you.
Some points to bear in mind before you run out and plant nothing but British native species in your garden: –
- Not all natives are good plants for bugs; some are just not that edible.
- It’s also worth thinking about the habitat in your garden; woodland plants will not thrive in a hot sunny border.
- Plus, there’s native and then there’s native. By which I mean some plants are native to a very localised area.
- And then there’s the whole issue about soil. Garden soil tends to be cultivated and nutrient rich. Many native species are used to an undisturbed, nutrient poor soil.
Plants for Bugs – What about the Humans?
Now there’s a question!
One of the complaints I hear about many native species plants is that they aren’t colourful enough, or they’re only spring flowering. Extending the range of ornamental, flowering plants is still good for the bugs and if it means we get more pleasure from our gardens it’s a win-win situation.
A dense planting scheme will generally provide a better display for you and support a greater number of invertebrates. However, if you’re gardening for wildlife, remember the vertebrates too! Some of them like dense cover, but some of the garden birds, blackbirds and sparrows for example, like a more open space.
As a designer and garden consultant I would be asking what you wish to achieve from your garden. That enables the right mix of habitats and plants to suit the use you want to make of your garden. For example, a play area for children, BBQ area for entertaining friends and the boring-but-necessary washing line. And still provide a biodiverse area for local wildlife.
The RHS study looked at ornamental plants in a garden setting, not at fruit and vegetables. As humans we are dependent on invertebrates for our food: about a third of our crops are pollinated by insects. But without the flowers to attract the bugs into our gardens and allotments, they wouldn’t be around to pollinate the food crops.
And if you’re a fairly regular reader of the Plews Potting Shed blogs, you may have realised how passionate I am about ornamental edible gardens. So let’s mix our flowers and foliage, edibles and ornamentals so we have plants for bugs and gardens for humans.
Related Gardening Blogs you may enjoy
Wild about Gardens – Design Ideas for Humans and Wildlife
Creating Small Wildlife Habitats in Your Garden
Bees Needs, National Pollinator Week and Your Garden
British Garden Birds in Winter
Green Living Water and Watering