Buckthorn for Brimstones

[selbypaul]

The Brimstone butterfly is seen by many keen butterfly enthusiasts such as myself as one of the heralds of spring. That fast-paced flash of bright yellow as they seem to be on a mission is something I remember well from my childhood in Chester every year.

But ever since I moved to Sheffield in 2004, until March 2020, I hadn’t seen a single Brimstone in Sheffield. That’s not to say they aren’t in Sheffield, they are, as the local reporting of sightings demonstrates. But numbers are low.

What changed in March 2020? Well in spring 2017, I removed the non-native privet hedge that was the back garden border between my neighbour and I, replacing it with Alder Buckthorn (rhamnus frangula). I did this purposely with the Brimstone butterfly in mind, as both Alder Buckthorn and Common (or Purging) Buckthorn (rhamnus cathartica) are their larval host plant.

I had read that the adult Brimstone butterfly can snip out Buckthorn from many miles away, and make a beeline for them. So, would I see a Brimstone straight after planting the 10-metre hedge line? Well, not straight away, but three years isn’t too bad.

It didn’t stay to lay eggs, but I did see it again in Spring 2021, so perhaps the plants are still too small, and they are just waiting.

Anyhow, in my part of south west Sheffield, we have an active community of residents who are interested in general wildlife and green issues, and I’m part of the committee of a new group called Nether Edge and Sharrow Sustainable Transformation (NESST). The group has nearly 400 members and is the successor group to the organisation that fought Sheffield Council so successfully to save Sheffield’s wonderful street trees, including the now famous 120-year-old elm tree on Chelsea Road. NESST is now focused on wider environmental, biodiversity and sustainability issues, not just street trees. Our motto is “Thinking Globally, Acting Locally.”

In early March 2021, I was chatting on the phone to a friend of mine called Julian Dowding, who lives in Ipswich about my Buckthorn hedge, and he told me about an initiative he and others had led in East Suffolk from 1998 onwards. The Brimstone butterfly was very rare in that area in 1998, but over a number of years, he encouraged local people to plant Common Buckthorn in their gardens and local green spaces. By 2010, the Brimstone butterfly population had “exploded” in Julian’s words!

Inspired by Julian, the next day I emailed the 400 members of NESST to see if they were interested in participating in a similar initiative. I knew we were reaching the end of the bare root delivery season, so I felt I had to act quickly, and gave people a week to respond. Amazingly, despite the short notice, and minimal advertising, I received orders for 180 plants from 28 people. You can see the locations of where the plants were planted in the map below.

Map of the locations where the 180 plants were planted in March 2021

Sheffield and Rotherham Wildlife Trust found out about my scheme, and we are currently working together to run a much bigger whole of Sheffield version of the scheme in September/October this year. Fingers crossed that should mean huge numbers of Buckthorn plants being planted all across Sheffield and nearby.

One word of advice on which species of buckthorn to choose. The basic information on the internet suggests choosing Alder Buckthorn for clay soils. However, speaking to the experts, Alder Buckthorn only really thrives on waterlogged acid clay soils. In all other conditions, Common (or Purging) Buckthorn is best suited.

The reason I’m writing this article is to encourage readers to do something similar in your towns and villages. The local scheme I ran this Spring probably took up a total of 24 hours of my time, spread over 2 weeks. I anticipate the same this coming autumn for the bigger Sheffield wide scheme. This is such a small investment of my time, for the anticipated gain of an explosion in the Brimstone population in Sheffield, in ten years’ time.

Practical conservation action is sometimes hard and arduous, but the Buckthorn for Brimstone initiative is quite the opposite. Why don’t you also give it a try?

[NickMorgan]

Excellent initiative. I live in the Scottish Borders and planted ten Alder Buckthorn in a new hedge I was putting in five years ago. Unfortunately the neighbouring cattle ate some of them, but I still have five small plants. I am hoping to get some more this winter to plant elsewhere.
We only get one or two stray Brimstones a year in this part of the world, but hopefully if more of us plant Buckthorn then we may be able to entice some to stay a bit longer. I may choose Common Buckthorn this time to see which does best.
Great to hear that the Elm was saved. I was wondering what had happened about that a few days ago.

[NickHull]

Here in Hull, pre-pandemic, we also had a Butterfly City initiative, planting alder-buckthorn. The City council bought 1,000 (small) bare-rooted specimens and they were distributed across the City and beyond. All went... However, not many of those not planted in gardens survived, being either too small to see-out a drought or cut-down by council contractors where they had been planted....
I purchased 25 2ft bare-rooted specimens; 3 have survived in our Green Corridor cycleway project and the rest in my or friends' gardens. Mine have attracted female Brimstones in their first year and Holly Blue this year. Getting them through their first years is key. We have purging buckthorn, but no noticeable Brimstone usage....
It is always a good idea to promote planting these small trees in public places. There are always groups willing to help; so long as the council also works to support these groups once the alder-buckthorn is planted, we should see more Brimstones

[selbypaul]

Excellent initiative. I live in the Scottish Borders and planted ten Alder Buckthorn in a new hedge I was putting in five years ago. Unfortunately the neighbouring cattle ate some of them, but I still have five small plants. I am hoping to get some more this winter to plant elsewhere.
We only get one or two stray Brimstones a year in this part of the world, but hopefully if more of us plant Buckthorn then we may be able to entice some to stay a bit longer. I may choose Common Buckthorn this time to see which does best.
Great to hear that the Elm was saved. I was wondering what had happened about that a few days ago.

Great to hear what you are doing Nick with the Buckthorn.

If you want to know more about the elm tree, it now has its own website, here: https://thechelsearoadelmtree.wordpress.com/

[selbypaul]

Here in Hull, pre-pandemic, we also had a Butterfly City initiative, planting alder-buckthorn. The City council bought 1,000 (small) bare-rooted specimens and they were distributed across the City and beyond. All went... However, not many of those not planted in gardens survived, being either too small to see-out a drought or cut-down by council contractors where they had been planted....
I purchased 25 2ft bare-rooted specimens; 3 have survived in our Green Corridor cycleway project and the rest in my or friends' gardens. Mine have attracted female Brimstones in their first year and Holly Blue this year. Getting them through their first years is key. We have purging buckthorn, but no noticeable Brimstone usage....
It is always a good idea to promote planting these small trees in public places. There are always groups willing to help; so long as the council also works to support these groups once the alder-buckthorn is planted, we should see more Brimstones

Absolutely, care and attention for all bare rooted plantings in their first year or two is key!

[NickMorgan]

Great to read about the Sheffield Elm. Long may it remain there. Do you know if it produces viable seed?

A friend of mine has just ordered some Alder Buckthorn plants to distribute around East Lothian. I suppose if we all do our part we will eventually produce a decent network of foodplants for Brimstones.

[selbypaul]

Great to read about the Sheffield Elm. Long may it remain there. Do you know if it produces viable seed?

A friend of mine has just ordered some Alder Buckthorn plants to distribute around East Lothian. I suppose if we all do our part we will eventually produce a decent network of foodplants for Brimstones.

Hi Nick.
Yes, absolutely, if only buckthorn was more easily available, it really would help the Brimstone. Well done for doing your bit.

The Chelsea Road elm in Sheffield is a Huntingdon elm, which is a hybrid of Wych elm and Field elm. As a hybrid, it doesn't officially produce viable seed. That said, when the elm expert David Herling came to visit me in 2016, he identified a younger elm nearby the main tree as a hybrid Wych elm x Huntingdon elm. Supposedly, there are infinitesimally small chances of Huntingdon elms producing the odd viable seed, and here was one rare example.

I have taken cuttings of the main tree, and they are highly vigorous. A 5cm cutting I took in May 2016 and that I planted on my garden border is now over 400cm tall, just five and a half years later! Fingers crossed the cutting also shows the resistance to Dutch Elm Disease that its clonal parent does.
Best Wishes
Paul

[NickMorgan]

I noticed that it said it was a hybrid, so I was thinking the seed may not be viable. Great that you have managed a cutting off it. The Wych Elms growing in my wood only reach a certain size before succumbing to DED. I have read that it is when they reach a certain height that the Elm Beetles get them, but I suspect it could be the girth of the trunks. The trees higher up the bank don't die before those below them, but when they get to the same sort of size.
White-letter Hairstreaks have been discovered in Southern Scotland in the last three or four years and they are not far from me. With a bit of luck I may find some in my Elms in the next couple of years.

[selbypaul]

All that is correct about elms Nick, yes. There are some fantastic DED resistant elms these days, bred specifically. Famously Ulmus New Horizon and Ulmus Rebona, amongst others. But one of the newest ones is the "Wingham Elm" which was the culmination of 40 years of work by Dr David Herling, just before he died.

[PhilBJohnson]

A “Thorny Brimstone Buckthorn" (Not acidic soil loving Alder Buckthorn).

Rhamnus cathartica was thought to be dioecious. ( Male plant & female flowers on different plants).
Female plants with flowers and berries, suitable for neutral and alkaline soil types (calcareous, chalk and limestone geology).
Locally common, it might not be.
An old name “Purging Buckthorn” might have meant that female plants with tummy upsetting berries, might have been less suitable, in some garden spaces or children’s play areas and other specific locations.
Please research this further with bespoke requirements in mind:
"It’s a fierce, invasive species in North America"
might have meant that it was not native there, so was not wanted as an "alien species"
Reference: https://www.woodlandtrust.org.uk/trees- ... buckthorn/

Possibly plant male plants for less fruiting berries, that a Brimstone Larva did not need, anyway. Once a suitable male specimen has been obtained, cuttings taken from that plant, should produce more male plants.

Common Buckthorn berries, bark and roots, were considered toxic to people. The berries, if eaten can cause severe cramping and diarrhea in humans.
Some advice, was to keep small children out of areas where Rhamnus cathartica berries fell, as the blue/black berries could be mistaken for commonly retailed blueberries and accidentally eaten.

Planting scheme
Female, native thorny Brimstone Buckthorn, might have been nice in native UK wildlife nature reserves, where UK native wildlife (including birds that didn’t have human stomachs), benefited from eating the berries.


Help more Brimstones.

[PhilBJohnson]

Leaves of a Blackthorn, might have looked superficially like those of a Buckthorn, when one was trying to identify them.
For Sloe Gin drinkers, collecting Blackthorn berries, might more than one mistake, have been made?
To be clear, as far as I knew, our Brimstone butterfly species, did not life cycle at all using Blackthorn as a larval food plant.

In Butterfly Conservation's "flagship magazine" Issue 139 Spring 2022,
Cover Image Rob Blanken showed an image of a Brimstone pair "hiding" under Crocus petals.
Page 23, there was an article titled: "Be more Brimstone"
And on Page 25 Conservation & Research, Ken Orpe described a limestone site then went on to mention:
"caterpillar food plants such as Alder Buckthorn (for the Brimstone)".

So lets not confuse people, the plant for calcarious geology soil types (Limestone) was native Rhamnus cathartica "Thorny Brimstone Buckthorn" (Much less locally common than Blackthorn in many places, possibly because of previous and existing planting schemes).
So if planting a less thorny, shorter growing Brimstone Bush (Alder Buckthorn) one might like to remember their Ericaceous compost!

Rhamnus cathartica & Gonepteryx rhamni, updated youtube video link:
https://youtu.be/RI4QetCXgTg

#PlantingPredjudice