Friday 18 December 2020

Working with Argyll & Bute Council to trial a change in verge cutting times

Islay's verges some already species rich, act as
corridors to species like this Marsh Fritillary 
With the likes of organisations like Plantlife promoting the leaving of verges to flowers and pollinators, cutting late in the season after the flowers have finished and many councils up and down the country adopting these new management strategies the idea that this would be of value to Islay has evolved.  Many of the planting strategies promoted by Plantlife and other organisations  however would not fit in the Islay context, striping away the existing vegetation and re-seeding with flowers when our soils already have a rich and area-adapted seed bank would be expensive and intrusive.  

Through the Pollinator Initiative, Islay Natural History Trust and funded by The Botanist Foundation a two year study of the less major Islay routes on the Rinns was undertaken in 2017/18 to understand the value and importance of the verges for flowers and pollinators locally.  This work has been reported on through past articles and talks.  The next stage was to use this knowledge and persuade the Council to adapt and change it's strategy on verge management, after much negotiating a trial has now been agreed.

Islay Natural History Trust (INHT), The Botanist Foundation and Argyll and Bute Council will work together in a trial to seed areas of verge with Yellow Rattle a native plant that parasitises grasses that will subdue grass growth with the goal of reducing the need for mid-season cutting.  The plan is to seed up to 4km of verge around the north of Loch Gorm and Gruinart with Yellow rattle this autumn.  Verge growth and development next season will be closely monitored and these areas will be cut late August or later after the plants have seeded.

If successful the outcome will provide long term benefits for both flowers, habitat and council budgets creating a win-win situation for both sides of the biodiversity and budget lobby.

INHT and The Botanist Foundation, who will fund planting and monitoring developed the plan in discussion with council leader Robin Currie and local roads and amenity team leader, Julian Green.  The group also talked about verges that provide space for many orchids including areas about Port Wemyss and Portnahaven and the Mulreesh road (near Finlaggan).  It was agreed that short sections would be left for the orchids to flower and be cut and maintained by volunteers to ensure road safety. 

This is a great collaboration and hopefully one that will be the beginning of an adaptive approach to verge management here on Islay and Jura.

Yellow Rattle will be used as our catalyst for the suppression of grasses, the growth of which ultimately creates the major need for cutting at all.  This plant is an indicator species typically found in ancient meadows, it is an annual plant and requires the ability to set seed each year in order to persist in the grassland.  It has a parasitic nature, its roots latching onto those of surrounding grasses pulling nutrients from the grass roots for its own growth, thus the grasses round about these plants grow with less vigour. 

 With grasses less dominant the height of verge growth will be subdued and the need for mid season cutting less urgent.  It also provides opportunity for other flowering plants like clovers to have space amongst the sward providing more flowers for pollinating insects.  Flower rich verges act as bridges across areas of sheep grazed pasture and barley filled fields linking many areas of great habitat that Islay supports.

A verge on the Isle of Lewis low
growing, and herb rich

 Our verges on Islay are a mixed bag, some all grass, rampant in growth, others a more colourful mix of flowers of varying height and visual intrusion into the road users awareness and some an important area for orchids and other specialist plants.  Despite this variety there is one management strategy, a process of cutting when machinery is available and when the control of growth becomes a visible need at the end of May and through to July to provide good line of sight for the driver and for the pedestrian to step off the road with safety.  This cutting is welcomed by some and the loss of flowers coming into their peak cursed by others.

So next year look out for the signs indicating that verges are being left for the purposes of letting flowers flourish and enjoy the colour and beauty our rich flora provides. 



The facts about Yellow Rattle

Some facts to consider:-

  • Yellow Rattle is native and a viable local component in grasslands within the area and in no way aggressive in the manner suggested.  It is already present in the verges less than half a mile from the trial site.
  • Yes some of the roadsides around Loch Gorm are already rich in diversity, the most diverse have yellow rattle naturally as part of their make-up with dense patches of red clover and bird's foot trefoil both extremely good pollinator species enabled to grow amongst this. 
  • The main section 2.5km that is within the trial however is the least diverse and heavily burdened with thick grasses which do not allow much other plant diversity to take hold, most likely the result of better soil fertility as they run alongside improved grassland with associated fertiliser spill off. 
  • The reason for only introducing yellow rattle is to subdue grass and enable a more open sward for other diverse seed stock within the soil to have the chance to develop. 
  • There is no guarantee that the seed will germinate, the grasses are dominated with Couch grass and Cock's Foot both aggressive dominant grasses, I know as I have physically hand scythed the area to prepare the ground for seeding, I wouldn't waste my valuable time if I did not think it was worth it!

Surveying the verges before trial. This verge shows
the barrier to seed spread that is along
most of the verge within the trial
The point raised as to the risk of spread into adjacent areas, is a viable point, one which has been considered.  In this instance the sowing is only within the one metre strip that the council cuts, bordering this on the full length of the roadside is at least a further 1-2m of thick matted grass, bramble, ditch or willow where stray yellow rattle seed will not take root and the adjacent grasslands are either sheep grazed or cut for silage which is likely to be before yellow rattle casts its seed and therefore the plant will not persist. 

Yellow rattle starts to develop and germinate in spring and completely dies at the end of the season, no roots or plant remains over winter.  Current farm management practices should naturally negate natural germination or development of cast seed and prevent spread of the plant beyond the verge area.

  • Fields are grazed by sheep prior to setting aside for silage and sheep will naturally graze out such growth.  I have witnessed sheep nipping off the flowering heads of yellow rattle so they will graze it out in preference and not enable seeding.
  • Once left for silage fertiliser encourages growth of grasses which will out compete species such as yellow rattle if they have persisted after sheep grazing.
  • Silage is cut earlier usually than the plant is ready to seed from late July onwards and even if it has got to the flowering stage will be cut and not supply the soil with seed for growth the following year.
  • There was mention of barley as a grass and hence would be adversely affected by yellow rattle. 
    • barley is not sown here until after the beginning of April and hence no yellow rattle would have grass roots to latch onto to germinate in time for the season.  
    • As far as I am aware all barley fields are sprayed with herbicide to kill off competing plants and therefore would kill off any yellow rattle which has germinated.

The problem for yellow rattle survival is that it is an annual and as such needs to seed every season to persist in the grassland.  Before the advent of early cutting for silage it would have been widespread in meadows cut for hay, modern farming has resulted in its wide decline and only persists where grasslands are regularly left uncut until late in the season, the large ancient meadow at Smaull Farm a prime example but this field is managed for this very purpose.  

INHT and The Botanist Foundation would never consider introducing any plant species that would cause harm to the natural environment.  This project is based on hard facts and consideration of scientifically collected data and not on a whim with disregard to the environment it will affect.  We would certainly not add yellow rattle in all areas, where verges are already species rich or the grasses already a minor feature, this would not add value to an already rich habitat.

Here are some links from across the spectrum including one from a farming forum where some consider they have some issue with yellow rattle, however most address the plant with the open outlook and consider the ease in eliminating it if some spread should occur.

Quote from Scottish Wildlife Trust information

"If Yellow rattle is no longer wanted on a site, flowers can be cut before they can produce seed and as there is no seed bank in the soil the plant will not appear the following year."

Fiona MacGillivray

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