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.

How Not To Plant “Woodland”

There’s a great and commendable enthusiasm about tree planting in the UK. We know the reasons why. Every year, especially when the floods come, people talk about the need for more trees. Tree planting might even be part of a new post Brexit agricultural settlement. We need to be careful about it, though.

There has been a great boom in tree planting in Ireland. Apparently forests covered less than 1% of the country a hundred years ago. That figure is now over 10% – still low. The government plans it to reach 18% by 2046. Hurrah! There’s a problem, though. This isn’t really woodland. The new planting consists of Sitka spruce plantations. Currently, only 2% of forest cover is mixed broadleaf woodland.

Is this an issue?

You bet.

plantation monocultureSitka spruce hails from the Pacific northwest. It’s not a great fit with local Irish ecology. It grows vigorously, and – as in the UK – advice is to plant at a tree per 2 square metres. Nothing grows beneath its dense stygian canopy. Unlike native broadleaf woodland, this monoculture needs fertilisers and pesticides. Plantations are springing up in bogs and across meadows. They might sequester carbon, they might have commercial value, but in biodiversity terms they’re… unhelpful.

Planting regimental ranks of broadleaf trees isn’t ideal either. Dense woodland, with no sense of the effects of what ecologists call succession, is sub-optimal. We need lower density mixed species planting, with gaps. This could be achieved by using a wider range of native species and by more extensive selective felling in any planting scheme’s formative stages.

woodland pastureContrary to earlier thinking, the chances are that dense forests didn’t cover Europe before iron age man started clearance work. More likely is that grazing livestock, like auroch and boar, chomped and rootled clear areas. These enabled much greater diversity of tree species, along with other flora and fauna. You can imagine Oaks establishing themselves among stands of Blackthorn, then spreading out. Wildflowers growing in sunnier meadows. Mottled sunlight through the canopy playing on a rich understory. More managed landscapes used to mirror this approach, which is becoming talked about again through the rewilding movement.

We’re surrounded by vestigial “wood pasture” in this pocket of Somerset. I’d love to see it restored. We should put a commercial value on that, payable from the public purse if necessary, as (I hope) we will – finally – do for planting for flood prevention.

I’m probably just cavilling about tree planting styles. Planting rates in England continue to be disappointing. Management of many schemes is poor and deer wreck others. England only has similar tree cover to Ireland. The government’s (unfunded) targets look like pie in the sky.

We need more trees, in a hurry. We should, nonetheless, get maximum value from them. They have to be the right trees, planted and managed in the right way.

The Cricket Field Oak

In winter when I do the washing up I can see the Cricket Field Oak. It’s usually through Somerset rain which, as you can see, has left its mark over the last several hundred years. I had to dash out to take this photo when the sun appeared briefly! This wonderful English oak, Quercus robur, was there centuries before cricket was played next to it and will stand for centuries after the last ball was bowled there.

Ancient trees
The Cricket Field Oak

It’s officially an ancient tree, with its own reference in the ancient trees directory, 46732. A minor celebrity – not that the family of Little Owls who live there would know. And I didn’t know either. I had admired and wondered at this single oak, but I didn’t realise it had been officially recognised. I’m indebted to the Ancient Tree Forum for this. They record our ancient trees and advise on their upkeep – invaluable work.

Why are these trees important? They support extraordinary biodiversity – English oak trees support over 280 invertebrate species, together with lichens and fungi. The older it is, the more diverse a tree’s associated flora and fauna becomes.

I love their cultural significance. Many are named after people or events that happened in their shade. Last year I visited Windsor Great Park. There I saw the great Signing Oak (13623), whose 9.72m girth dwarfs our little Cricket Field Oak. South of us here is the equally enormous Wyndham Oak (6884), where Sir Hugh Wyndham took his ease in the 1650s. These trees are over 900 years old.

We are blessed with ancient oaks in this corner of Somerset. We live on what was the edge of the great royal Selwood forest, where Alfred gathered the fyrd before the battle of Edington*. Later, the land hereabouts was wood pasture, used in the middle ages for hunting deer, grazing domesticated animals and producing timber. This open environment is ideal for single oak trees, hungry for light, to flourish. Many of the oaks were managed carefully and pollarded, which has extended their lives.

It’s an accident of history that these trees weren’t felled. They would have been on mainland Europe. For this we can be grateful for the failure of the Commonwealth and – shortly after – John Evelyn’s Sylva. Deer parks were the preserve of the Crown and aristocracy, who came to appreciate the value of trees in the landscape.

Oaks are said to spend 300 years growing, 300 years maturing, and 300 years “veteranising”. There’s no hard and fast rule as to when a tree is a veteran and when it becomes “ancient”. Just down the road from us over the road from the pub is a fabulous ash tree (55789), which is officially a veteran; it’s a mere 5m round.

This ash is a big tree, but as it gets older, like an old man it will shrink. Its trunk will continue to thicken but its crown will reduce as a survival strategy to reduce the ravages of weather and decay.

These ancient trees are extraordinary. They are their own secret worlds, teeming with life. They have their own told and untold histories. Older and more mysterious than cathedrals or castles. Worth more pondering while doing the washing up.

*The night before the battle (in 878) Alfred stayed by the great Iley Oak, which was still used as a gathering point in the 1650s.