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Native Or Non-native Plants?

We need to improve vetting of plant imports, and it's great that we have a new Plant Biosecurity Strategy.

Ben Goldsmith commented on it:

Planting non-native, exotic plants in the back garden is really naff (who wants a garden that looks like a municipal roundabout?). Imported plants also... do nothing for wildlife! 

Ben was a non-executive board member at DEFRA and is a leading proponent of rewilding; I think it's fair to say he's one of the most influential voices in the current debates about nature in the UK. It makes this comment doubly surprising. 

Where Is A Plant From?

First off, not all non-native plants sold here are grown abroard. And many "native" plants are imported. Ben has conflated two separate issues. We should - absolutely - all try to buy UK grown plants, and not just because of the risk of disease. This has been a crusade of mine for years. With luck this will lead to the revival of UK growing nurseries - it's almost impossible currently, for example, to buy UK grown bulbs.

Definitions

Secondly, I'm not sure I understand which plants Ben had in mind. What is a "non-native" plant? "Native" and "non-native" are slippery definitions unless you're a botanist. Perhaps he was thinking about the kind of annual bedding you used to see all over the place - less so now. There are all sorts of non-natives, of course, many of them very wildlife friendly, as opposed to Ben's roundabout.

Is Prunus cerasifera "non-native"? It's probably a Roman introduction, so technically an archaeophyte. Or how about Horse chestnuts and Snowdrops, much more recently introduced neophytes? Fruit trees are all "non-native" - they are grafted cultivars - yet orchards are amazing biodiversity hotspots. 

More recent arrivals can be more or less exotic. We have a fantastic native Echium here, for example, Echium vulgare (Viper's bugloss, photo above), which is the most amazing nectar source for a wide range of pollinators. There are other Echiums scattered around the Mediterranean; the closely related Echium pininana has made it to Cornwall, where it's a familiar garden escapee. 

The Case For Native

We've underplayed the importance of native plant species for our wildlife for too long, it's true. Wildlife NGOs and commercial interests alike have been guilty of this. It was one of the reasons I set up Habitat Aid in 2008.

Generally speaking, the longer a plant has been here, the more animal species are dependent on it. These are mostly invertebrates, whose larval stages eat food plants like oak and willow. An estimated 2300 species depend on oak trees. Because these plants support large invertebrate populations they're also associated with lots of animals further up the food chain - bats and birds, for example. 

Specialist invertebrates also rely on specific native species for homes. Some depend on only one species for nectar or pollen, like the Hawthorn mining bee. Further up the food chain there is a raft of small mammals and birds which depend on native plants for food and protection. A recent survey found over 2000 species in a 90m length of hedgerow. 

Even pollinators tend to prefer native plants for pollen and nectar when given the choice. Recent RHS research showed just this (broadly speaking, the further away the origin of a plant species, the less attractive it is as a nectar source). This - and the food plants and habitat they provide - is one of the reasons why wildflower meadows are so much more beneficial to wildlife than pictorial meadows. 

BUT...

...what wildlife actually needs in our gardens - now more than ever -  is a combination of native and helpful non-native plants.

While I admire the beauty of many of our native plants - like Viper's bugloss - and love planting them to create habitat, lots are er... less exciting looking. The buckthorns (above) are a good case in point - fantastic for wildlife, but with an altogether lower key aesthetic appeal. We have native plants in our formal and forest gardens here, but I'm always going to have a majority of non-natives in these areas; that's sort of the point. After all, I've got exclusively native plants everywhere else - on our green roof and in our hedges, meadow areas, and the pond.   

Diversity Is The Key

Some of the more or less exotic non-native species actually have an increasingly important place in the ecosystems in our back gardens, to help our native fauna battle climate change. Why is this?

Many are increasingly valuable to pollinators. These animals are increasingly active all year round as it becomes warmer. The Buff-tailed bumblebee is just one example, now fully active all year round in urban areas. Which native plants are in flower for it to forage from in winter? There aren't any. Bombus terrestris depends on "exotics" like mahonia, sarcococca, Arbutus unedo (the Strawberry tree, above), or Winter flowering cherry - you get the idea. Suburban gardens with plants like this are great habitat for invertebrates. In more rural  settings, the Prunus cerasifera I mentioned before is an increasingly important plant, flowering ahead of its close native relation, Blackthorn. 

Berberis cultivars and cotoneasters rub shoulders with native plants like Rowan and Hawthorn in any top 10 of berrying plants. Unused fruit is a boon for invertebrates including butterflies and wasps, as well as small mammals and birds. It could be hedgerow fruit, or it could be from cultivated trees and bushes. I doubt dormice notice the difference between hazelnuts and cobnuts. 

Climate change presents a fundamental challenge to our native flora. It's happening so quickly that plants have no chance to adapt to it. Many species will at best endure terrible stress as they try to cope with a temperature range of 50 degrees and alternate spells of flood and drought. It's terrible to think of it, but species which are common today might disappear. We have to build resilience into the landscape.

This is much more easily done in the garden. Introduce as much diversity as you can. My top ten plants for bees has all sorts, for example. Even non-gardeners can grow plants from hotter climes like Rosemary and Lavender, or Stachys Byzantina. Easily bought as British grown. And you can hardly argue they're naff.