Foodplants for Butterflies and Moths

What would you think about if I asked you for good foodplants for butterflies and moths? Buddleja? Verbena bonariensis? Hebe?
It’s true – they’re all great nectaring plants, and non-native to the UK. So why should I bother with native plants if I want to encourage butterflies and moths?

Well, many native plants are very good sources of nectar, of course. Hemp agrimony, knapweed, honeysuckle, wild marjoram and field scabious spring immediately to mind. These are all attractive and in some cases long flowering wildflowers. As nectar plants are they as good as the ornamentals? It’s a far from straightforward question and not my topic here!

Celastrina argiolus
Holly Blue on Holly leaf
Where native plants incontrovertibly DO win is as foodplants for caterpillars. British caterpillars, by and large, need British plants to munch. This can, of course, extend to cultivars, which explains why cabbages are regularly written off. There are exceptions too; I offer up nasturtiums (from South America) in my veg patch as a sacrifice to happy Small White caterpillars.*

At this point gardeners say they have a nettle patch for caterpillars. Well yes – good foodplant but not enough on their own. Atropos Publishing has a good guide which shows which species of butterfly and larger moth depend on which foodplant. Urtica – nettles – have 35 associated caterpillars. It highlights the difference between imported plants and native. Buddleja are a good example; the book lists only 3. This is very different to a native plant – field scabious has 14.

Grasses too are good larval foodplants, which is one of the reasons why we encourage people to sow meadow mixes rather than just wildflowers. Cocksfoot, for example (although not ideal for a meadow), comes in as supporting 35 different types of caterpillar.

Trees and hedge species are even better. Sometimes they have almost exclusive or totally exclusive relationships with individual plants. I think of Yellow Brimstones and Buckthorn, Purple Emperors and Oak, Brown Hairstreak and Blackthorn. The king of all our plants is the Oak; according to the book, both oaks support over 120 types of moth and butterfly caterpillars. It’s said an oak tree will lose around half its leaves to insects in an average year.

Which are the top five foodplants? They’re all native trees or shrubs:
English and Sessile oaks (Q. robur and petraea)
Willows (Salix spp.)
Birches (Betula spp.)
Hawthorn (Crataegus spp.)
Blackthorn (Prunus spinosa)

*and thence happy blue tits etc.etc.

Native And Exotic Plants In The Garden

Robin Lane-Fox wrote a bad tempered piece in last weekend’s FT about “exotic” v. “native” plants in the garden. He’s a respected plantsman, and so I wasn’t surprised to read he was against using native plants in the garden. I’m entirely sympathetic to this view; we are all masters and mistresses of our own gardens, and should do with them whatever we most enjoy. What did surprise me, however, is that he repeated the mantra that our wildlife was oblivious to the difference between (plain) native plants and attractive exotics. It’s true that disease threatens many of our “native” tree species. Sadly we would do well to think about alternatives for planting schemes. When we do, it would also be advisable to source them from UK nurseries so that a raft of new diseases doesn’t reach our shores. Improved biosecurity and more UK grown plants may be rare Brexit dividends.

Plants for Pollinators
It’s also right that “exotic” plants can be at least as beneficial to some wildlife as “native” plants – in some cases more so. Many bees, butterflies and other pollinators benefit from the longer and different flowering periods. There’s also the heavy nectar production of some attractive exotic flowers. We sell a fantastic seed mix from Flowerscapes which illustrates this. However – and this is a big but – it’s wrong to think of plants purely as providers of pollen and nectar. Even if we did there are bee species which are oligoleges – i.e. they feed from a specific plant genus or even single plant species.

Plant Food
I imagine there are no Brimstone butterflies in the doubtlessly beautiful Lane-Fox garden. Brimstone larvae dine exclusively on the leaves of one of our dullest looking shrubs, Buckthorns*. Many moth and butterfly larvae have similarly exclusive or nearly exclusive relationships with other native plants as do many thousands of insects. This includes the Blackthorn so disliked by Mr Lane-Fox.  Quercus robur – that’s the English oak, not your imported tat – supports up to 400 different species of herbivore insects in the UK. This kind of dependence is true of amphibians and mammals – no boring old hazel, no boring old dormice.

My own garden is less ornamental and more nature reserve, but that’s what gives me pleasure. It’s a smorgasbord of natives and exotics, vegetables and fruit trees. It’s also full of the munching, buzzing, swimming things which can’t survive in the surrounding farmland.

*Our bees also seem very partial to Purging Buckthorn‘s inconspicuous little flowers.

Plants for Bugs

Last week the RHS published the first paper from its “Plants for Bugs” four-year study in the Journal of Applied Ecology. It’s an interesting read, not least because so little research has been done in this area. According to the RHS website the key messages for gardeners are:

The best strategy for gardeners wanting to support pollinating insects in gardens is to plant a mix of flowering plants from different countries and regions.

Emphasis should be given to plants native to the UK and the northern hemisphere, though exotic plants from the southern hemisphere can be used to extend the season (there are a greater proportion of exotic plants flowering later in the season compared to UK native and northern hemisphere plants) and provide nectar and pollen for some specific pollinators.

Regardless of plant origin (native or non-native), the more flowers a garden can offer throughout the year, the greater the number of bees, hoverflies and other pollinating insects it will attract and support.

This is all good stuff, and I absolutely agree with it. But – and you knew there was a but coming – I do have two complaints about the way this is being spun.

First off, there’s a question of emphasis. The accompanying social media blurb from the RHS says:

Native plants alone may not be the best option for supporting pollinating insects in UK gardens!

Well, yes, but non-natives alone DEFINITELY aren’t. I can’t see the headline reading “Exotic plants alone are definitely not the best option for supporting pollinating insects in UK gardens” Perhaps I’m just being over-sensitive, or perhaps not. The RHS are hardly likely to discourage people from growing exotic cultivars, after all – it’s what they do.

Secondly, identifying what provides the “best” nectar and pollen for certain pollinators is very helpful, but it’s not the bee all (geddit?) and end all. Take butterflies, for example.

Like some solitary bees and many other “bugs” they have developed relationships with very specific plants. In the case of butterflies it’s as food plants for their caterpillars; Yellow Brimstone caterpillars eat Buckthorn, for example. I know some butterflies and moths can adapt to non-native plants, but not all. It’s also true that some of our own insects like non-native plants for non dietary reasons; the wool carder bee just loves Stachys byzantina, with which it lines its nest.

In other words, choosing plants for bugs is not just about native v. non-native or pollen and nectar. It’s more complicated than that. As usual.

Honey bee
One of our honey bees enjoying a non-native scoff from Geranium ‘Rozanne’, a favourite in the garden

Viper’s Bugloss (Echium vulgare)

Echium vulgareViper’s Bugloss is one of my favourite British wildflowers. It looks like a kind of poor man’s Delphinium, but flowers for ever and it’s just great for bees. It’s not an antidote to snake venom though, which belief is why herbalists gave it its common name. “Bugloss” supposedly derives from the Greek word for ox-tongue, which describes the plant’s leaves.

It’s unusual to find a flower like Viper’s Bugloss which attracts all sorts of bees – honeybees, bumblebees and solitary bees. Butterflies and moths love it too.

Viper's BuglossHoneybees have shorter flatter tongues, so for nectar they tend to visit more open platelike flowers with relatively easily accessible nectaries but relatively low reward.

Bumblebees have longer tongues, up to 13mm for Bombus hortorum, which means they can access nectar hidden at the base of flowers with long floral tubes. These include wild Red Clover, Foxglove, vetches and Bird’s-foot trefoil.

Solitary bees cover the gamut of tongue lengths. They’re mostly short tongued, so prefer low reward, easy access flowers, but some, including leafcutter bees and mason bees, have relatively long tongues and go for restricted access flowers with higher nectar rewards.

The story for pollen is slightly more complicated; we’re beginning to understand the importance of diversity of pollen in diet for all bees. Some plants have relatively high protein in their pollen and seem to be preferred. Viper’s Bugloss pollen has three times the protein value of sunflowers, for example, according to Plants For Bees, the bible on this sort of thing.

It’s not just the features of flowers which folk should be considering – it’s the time they’re in flower. Good plants flowering outside periods of high nectar flow are invaluable. This obviously includes late autumn and early spring, but there’s also a shortage in mid summer which beekeepers call the “June gap”. Lavender is a great bee plant from this point of view – as is Bugloss.

Echium vulgareLast – but by no means least – there’s the look of the plant. I’m not having plants in my garden I don’t like, however good they are for butterflies and bees. Viper’s bugloss looks lovely to my eye, and has a nice strong, upright habit. It likes poor well drained soil and tolerates drought well – it does well on our roof, for example. It’s biennial but self seeds, so once you’ve got it you’ve got it! I love it in blocks, where it’s dark blue makes a striking – and buzzing! – statement in our gravel garden next to some Nepeta.

The Invertebrate Conservation Conference

Last week I had a very jolly day in London at the Invertebrate Conservation Conference. The presentations were generally high quality and surprisingly accessible to a non-specialist like me. The speakers and audience were enthusiastic (which I was expecting) and pretty youthful (which I wasn’t).

They need that enthusiasm. By definition I suppose conservation is a pretty depressing business. You’re dealing with a series of compromises and setbacks as humans barge their way into the largely unknown and unprotected natural world. These get worse when money is tight, particularly in a Cinderella area like invertebrate conservation. As the Earl of Selborne pointed out, we need to dramatically revalue our natural capital. The destruction of peat moors in South Yorkshire offered a shocking and graphic illustration of what has been going wrong.

I was prepared for some frustration and anger, but not for the good humour and entertainment value most of the speakers offered by way of contrast. And what great bizarre facts! I bet you wouldn’t guess there are 5 tonnes of animals in the soil of an average hectare in Europe? That’s half a kg per square metre. A lot of worms and, as I learnt, Collembola.

My take-aways from the conference? There are some really good pragmatic and effective projects going on, bring together local initiatives into bigger schemes. These include Buglife’s B-Lines, Butterfly Conservation’s citizen surveys and the Environment Agency’s work with sea walls in Essex and East Anglia, for example. Invertebrate charities are tiny, but they are among my favourites in the conservation world in terms of their aspirations.

Our continuing lack of knowledge about what’s going on in our own environment is as astonishing as it is potentially damaging. Generally, though, the dual threats of climate change and habitat loss are wreaking terrible damage on our invertebrate populations. So far as we can tell. These charts are, unfortunately, typical of the current situation. They show the distribution of the Wall butterfly Lasiommata megera in 1970-1980 and over the last 4 years. They’re courtesy of the National Biodiversity Network, another great organization we support and whose conference will be another jolly day in London.

Butterfly conservation
Distribution 1970-1980
Butterfly conservation
Distribution 2010-2014

Native and non-native plants

AstersToday’s papers reported on an RHS study which looks at “whether the geographical origin of garden plants makes a difference to the abundance and diversity of garden invertebrates.” According to the Independent:

“The idea is solidly out there that if you want native insects you should only plant native plants*. That’s been the advice for years. Initial analysis shows this is not the case,” said Mr Salisbury, though he cautioned there was much more detailed analysis to be done.

You might expect this conclusion from the RHS, who are hopelessly compromised in areas like these, and you might expect me – a seller of native plants – to get cross about it.

It’s difficult to comment on the paper as I wasn’t invited to the meeting at which the preliminary results were leaked, despite asking to be. I’m not in any sort of position to comment on the project’s methodology or whether its conclusions are right or not, which in itself is not very clever (the people who were there – like Buglife – seem dubious).

I do think the way they are presented perpetuates the polarization of this argument. Why does it always have to be natives versus non-natives? Why not mix the planting up in a garden? Excuse the language, but it’s utter bollocks to say “The idea is solidly out there that if you want native insects you should only plant native plants”. The idea isn’t solidly out there at all and, of course, isn’t necessarily so, although the reverse is – if you don’t want insects only plant (certain kinds of) non-native plants.

And this is the danger; the way this is presented is potentially disastrous. “British wildlife… can thrive on non-native plant species” is the way the Independent has reported the story. Of course it can – some wildlife can thrive on some types of non-native species. And I don’t think they’re suggesting 300 year old hay meadow offers the equivalent habitat to a selection of bedding plants from B&Q. Or maybe they are?

It might suit the project’s authors to sensationalize its findings when they are properly released, but we’ll all be the losers when they do.

*Native plants are species which arrived in Britain after the last ice age without human assistance, by the way. This surprisingly includes species like Raspberry!

There’s No Pleasing Some People…

Bumblebee Queen on GeraniumWhat a fantastic summer we had. And it wasn’t just us enjoying the sun – all sorts of other animals had a great time of it too. Invertebrates generally had a very good year. The few species we try to count showed that. Butterfly Conservation‘s annual citizen survey recorded nearly twice the numbers of individual butterflies than last year, with its miserable excuse for a summer. We even had the beautiful Clouded Yellow in Somerset, in numbers I had never seen anywhere before. There have been huge numbers of fat new bumblebee queens about. You can bet honeybee numbers will turn out to be good this year too, as colonies have been able to forage all through the summer, untroubled by cold and wet.

This is obviously good news, but there is a hidden downside to it, which Butterfly Conservation’s Richard Fox hints at:

It reminds us that butterflies are resilient and will thrive given good weather and suitable habitats. The problem facing UK butterflies is not the notoriously variable weather but the way that humans manage the landscape

Hmm… well, while “variable weather” might not be a threat I think climate change is. If cold wet summers become much more the norm then we’ve got problems.

Whatever; the weather does detract from the key message of the invertebrate charities that we work with – the habitat bit. And that’s a problem. We have a good summer and there are buzzing, crawling, flying things everywhere. People ask themselves if there really can be a problem with habitat loss. We have a cold wet summer and that gets the blame for plummeting invertebrate populations. In either event there’s not very much they can do about it, which makes for fatalism and disengagement. Compared to a series of miserable weekends in July, habitat loss is a pretty intangible concept too. Tricky.

Moths And Butterflies: A Life Lesson

Acronicta rumicisMoths and butterflies offer a useful lesson in growing up.

The most attractive children often grow up to be the dullest adults. My most glamorous classmates have gone on to be accountants and solicitors. The record producer and the brain surgeon were pretty inconspicuous at school, so far as I remember. There are some exceptions, of course, like the Elephant Hawk Moth – spectacular in its youth and spectacular as an adult.

I think this exotic caterpillar chomping my Purple Loosestrife is the larval stage of the Knot Grass, Acronicta rumicis. The adult is – well – one of those moths which is beautifully camouflaged against bark. Like an accountant on the 6.15 London Bridge to Purley.

It turns out the Knot Grass is a pretty promiscuous eater, which is lucky for it. There’s recently been much focus on which plants are good for pollinators, but not very much on which plants are good for which caterpillars of moths and butterflies. People talk vaguely about nettles, which are indeed a foodplant for a number of moths and butterflies, but different butterflies and moths need all sorts of different plants. Most of these flowers and grasses are native, of course. Many are rather more attractive than nettles, which are not a great favourite of mine (sorry!). The keys to planting them, as usual, are diversity – diverse flora, diverse fauna and volume – clumps are good for short sighted moths and butterflies.

Brimstone Butterflies

Brimstone butterflies
Photo: Peter Eeles
Brimstone butterflies are one of my favourites. I’m not a very clued up lepidopterist, but Brimstone butterflies I can ID a mile off. They’re yellow – the books say the males are rich yellow and the females lighter, although to my mind they’re yellowy green. I saw my first of the season on a run yesterday, in between yelling at the dogs and feeling genuinely hot for the first time this year. She was unmistakably yellow (green), and with the shape peculiar to Brimstone butterflies. She was fluttering about along a woodland margin – very typical. They’re not only easy to spot, but one of our most attractive and long lived butterflies too. See Brimstone butterflies at this time of year and they’ll be adults emerging from hibernation, a real harbinger of spring. The next generation start flying around August.

Brimstone butterflies food plantI particularly like them because of their relationship with Buckthorn. Brimstone butterflies’ larvae feed exclusively off our native Alder Buckthorn and Purging Buckthorn, Rhamnus frangula and Rhamnus cathartica. If you grow them, as we’re doing, chances are you’ll find Brimstones moving in sooner rather than later. They stay for successive generations, year after year. Buckthorn is critical for Brimstone butterflies’ survival.

There are many other similar exclusive relationships between our native flora and fauna. Insects don’t just need flowers to provide nectar and pollen; they often have other demands on them too. These mean it’s easy to play God. If you want Brimstone butterflies, plant Buckthorn. Small Blues? Kidney Vetch. I love the sort of immediate cause and effect you can get in your garden.

Buckthorn is a nice easy-to-grow native shrub anyway. We’re growing Alder Buckthorn here, as it copes so well with our waterlogged clay. Purging Buckthorn is more of a chalky soil lover, so wherever you are, you can give Buckthorn a try!

The Extraordinary Ordinary

I had a lovely start to the day when I stumbled across this video on You Tube*. It’s a short French film released a while ago. Normally I’d just Tweet it or stick it on Facebook, but it’s really lovely. It’s a celebration of the microcosmos around us – a sort of Gallic David Attenborough documentary on our insect world without David Attenborough.
It well illustrates the profound delight that can be had from creating these kind of pulsating ecosystems in our own gardens and fields. This is one of the key messages we’re trying to get across. Enjoy.

*Thanks @ReadingUrbPolls on Twitter.