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Native vs non-native plants – what’s really best for wildlife?

Bumble bee - credit Patrick Steen

We’re often told that native British plants are better for wildlife than cultivated plants introduced from other countries, but have you ever wondered whether anyone told the insects?

I work on plant trials at Capel Manor Gardens and last year I was recording information on a trial of native wildflowers. I noticed that some of the cultivated foreign plants we were growing in other trials were attracting at least as many insects as the natives, and often more.

I started to wonder about the advice that’s often given about the types of plants we need in our gardens if we want to provide food for insects. It’s usually suggested that native wildflowers are better than cultivated plants, especially if they’ve been introduced from other countries. Yet, from what I could see, that just didn’t seem to be the case – the plants I’d noticed being mobbed by bees were Heuchera and Penstemon, both intensively-bred North American natives.

When I looked into this further, I soon realised that there’s currently quite a lot of research being done on this very subject and even the experts concede there’s a lot we still don’t know.

Best plants for wildlife – the expert view

Plant biologist Dr Ken Thompson explains in this month’s Which? Gardening magazine that even the term ‘native’ is misleading, since after the last ice age Britain was colonised by many plants from other European countries. We also have many plant species (and insect and animal species for that matter) that are related to plants from other northern hemisphere countries to which we were physically linked to in the more distant past.

The RHS has also carried out a three year trial called ‘Plants for Pollinators’ and found that pollinating insects don’t discriminate between native and non-native plants. And its’ findings back up previous research by the University of Sussex.

Insects’ favourite flowers

Of course, there are certain types of cultivated plants that don’t suit pollinating insects, such as plants with very full double flowers where many nectaries are replaced by petals. That means it’s not a good idea to pack your garden with frilly doubles at the expense of simpler flowers, such as lavender, which we all know attracts bees.

But did you know that even among lavenders, insects have their favourite types? Lavender x intermedia has proved to be more popular than either English or French lavenders, which are much more commonly grown. In our trial garden the plant that really caught my eye was Penstemon ‘Riding Hood Lavender’, which was visited by far more bumble bees than any other plants. So far it seems no-one fully understands why insects have these preferences.

The research continues. This year we’re hoping to help the Wildlife Gardening Forum, a group of wildlife experts from various organisations, with some citizen science that’s being carried out by nearly 2,000 Which? Gardening members. They’re growing three different sunflowers, a couple of varieties that produce pollen and one bred not to produce it (for the cut flower industry). We hope to see whether or not this makes a difference to insect visitor numbers.

It’s just one small step towards providing more answers to some of these vital and complex questions. In the meantime, I’d like to know whether you’ve noticed any plants in your garden, native or not, that regularly buzz with bees or attract butterflies? Do you have a native wildflower meadow, or an area in your garden that you’ve planted up deliberately to attract pollinating insects? Is it doing its job?

Comments
Member

The top priority must be to consider whether non-native plants could grow out of control. That can be difficult to predict. I know of one plant that is scarce in one country but scarce in another.

Anyone familiar with Japanese knotweed and other invasives will be aware of the problem. That reminds me that I need to try to persuade a group of volunteers to come along for a ‘Balsam Bash’. Thankfully, Himalayan Balsam pulls up easily.

Member

I agree that the term “native” can be misleading. I often wonder how it’s fair to term something an “invasive” species when really it could just as easily be described as a “thriving” species that is successfully colonising a new area. When a species is no longer found in an area is there really a need to be so sentimental about it? If insects do not discriminate between “native” and “non-native” species why should we?

Member

To describe invasive species as thriving is a bit of an understatement. One example is Japanese knotweed. It’s great for bees and other insects, but it spreads so prolifically that you may not get a mortgage if you are planning to buy a property with Japanese knotweed in the garden.

The problem was discussed in a recent Conversation:
https://conversation.which.co.uk/energy-home/japanese-knotweeds-killing-your-mortgage-chances/

Member

Introduced species can cause problems but aren’t all invasive by any means. There are plenty of lovely plants that are as good for wildlife as natives and that thrive in the UK. Diversity in our gardens should make them richer places for us and the wildlife.

Member

I agree, Janice. We just need to be careful about what we introduce.

Gardens could become more important as habitats for bees and other insects thanks to the amount of pesticides used in agriculture.

I was unaware of the fact that double flowers are of little use to pollinating insects.

Member
Davina Wynne-Jones says:
24 May 2013

I find opium poppies are the favourites for bees at dawn, and comfrey is their choice at dusk. Butterflies like echinacea. I grow all medicinal plants and have loads of insects.

Member

I wish we could do more to persuade people that paving their gardens does not necessarily make them more easy to deal with – it costs and creates new challenges and expenses.

Let’s have more promotion of ideas for gardens with plants grown in smaller areas of soil (rather than pots which with lack of attendance will most likely die and then not be replaced) and plants which need a little less maintenance. Let’s hear more about irrigation systems. It’s not just the bees which are suffering now or will in the future – it’s the other wildlife – and the problems of flooding that are being created by concrete gardens.

Member

I planted up a new ‘butterfly & insect’ border last year. Butterflies and hover flies and bees seemed to feast on the Verbena Bonariensis throughout the season. Yes they liked the Buddleia and Lavenders, but the Verbena were definitely the favourites by far.

Member
Jeremy Millen says:
14 December 2014

In my experience, there are native and non-native plants whose flowers are attractive to pollinating insects and that have seeds of nutritional benefits for birds. For example, bees love the native Hedge Woundwort, Viper’s Bugloss and Hemp Agrimony in my garden but also the non-natives, like Lemon Balm, Michaelmas Daisies and Echinacea.

However, an additional issue to consider is the value of plants to the birds that depend on the larval stages of insects who lay eggs on the plants, (e.g. caterpillars) for food. From what I have observed, native plants are generally more beneficial in this regard. I understand that the breeding success of birds that nest in gardens is usually poorer than those birds that nest elsewhere, because gardens usually lack the quantity of insect larvae needed for the parent birds to raise healthy chicks, due to an insufficient.quantity and variety of native trees, shrubs and plants.