Outside the Mount Stuart visitor centre. (Photo: Stewart Wardrop)
Mount Stuart house and gardens on the Isle of Bute were the destination for this summer’s Scottish branch field trip on 13 June.
While much of the UK was being hit by torrential rain the West Coast of Scotland didn’t live up to its reputation and was surprisingly dry as the group congregated for tea and coffee at the estate’s modern visitors centre. AA Chief Executive Stewart Wardrop, who travelled up for the day from HQ with Senior Technical Officer Simon Richmond, welcomed the attendees and thanked the Bute Estate for hosting the event.
A morning of interesting talks followed, beginning with an introduction to the site from Dom Murray, Head of Horticulture. Dom gave a passionate talk covering a multitude of subjects relating to the history and management of the 670-acre designed landscape that includes Mount Stuart house, its arboretum, pinetum and rock garden.
The estate was originally owned by the Bute family whose third earl was one of the founders of Royal Botanic Gardens at Kew in London. Ownership of the estate is now in the hands of the Mount Stuart Trust which ‘is committed to the conservation, preservation and maintenance of the house, estate, gardens, collections and archives for the benefit and enjoyment of all’. With concerns about the consequences of climate change on the estate, the trust has developed an ambitious 20-year strategy to bring together different interest groups to help protect this important landscape. Education will be at the heart of the strategy, with opportunities to collaborate and share skills with institutions including the University of the Highlands and Islands. There is also a plan to convert the visitor centre into an arb and horticulture learning centre.
The estate contains many impressive trees and is part of the National Tree Collection of Scotland. It also provides a home for a number of endangered conifers collected as part of the International Conifer Conservation Programme. In 2014 the estate received funding from the National Tree Collection of Scotland to enable the drafting of a management plan to protect the designed landscape and enhance the national tree collection. A number of trees were identified as being in a state of decline and in 2016 the estate began working with Bartlett Tree Experts to implement a tree restoration programme across the site. Our group had a chance to see first hand some of these trees and the methods of treatment used.
Standing at the top of the Lime Avenue. (Photo: Nick Porter)
Walking through the pinetum. (Photo: Nick Porter)
A Spanish sweet chestnut planted in 1717. (Photo: Nick Porter)
Bartlett Tree Experts demonstrating the air spade as part of the root zone invigoration programme. (Photo: Nick Porter)
Dom handed over to Plant Diagnostician Dr Jon Banks from Bartlett Tree Experts for his talk entitled ‘Tree pests and diseases – What’s new, what’s on the way, what we can do?’. Jon began by describing some of the pests and diseases already affecting trees and shrubs in Scotland including box blight and the conifer tip miner. The group spent some time discussing ash dieback and at what stage trees should be felled after infection. It was pointed out that it is important not to pre-emptively fell healthy ash as we could lose trees with natural genetic resistance to the fungus as a result.
Jon went on to talk about pathogens that are not currently in the UK but that, due to factors including poor plant biosecurity and climate change, could make their way here in the coming years. A particularly worrying prospect would be the introduction of the bacterium Xylella fastidiosa with its wide range of host woody plants including maple, oak and elm. Another concerning pathogen not currently present in the UK but that could have dire consequences for the Caledonian pine forests in Scotland is the pine processionary moth. Like the oak processionary moth that is now in the south-east of England, the hairs of the pine processionary moth are toxic to humans, and it is a severe defoliator of pines. The caterpillar can also feed on larch and cedar, making its potential impact even more damaging. Jon finished by talking about the options available for identifying pathogens on trees and shrubs in the UK. Bartletts have a laboratory in Reading with sophisticated diagnostic equipment where samples can be sent for identification. Good quality photos can also be sent to aid the identification process.
Trees to marvel at
After lunch, kindly provided by Bartletts, the group headed out for a tour of the gardens led by the Living Collections Manager, Graham Alcorn. Early into the tour the group stopped in the pinetum to marvel under giant Douglas firs (Pseudotsuga menziesii) and Corsican pines (Pinus nigra). Graham explained that many of the trees in the collection are wild, collected from countries including America, Mexico, Chile, Taiwan, Japan and New Zealand, and therefore have important genetic diversity.
We then moved on to Lime Tree Avenue that was originally planted by the third earl in 1734 and replanted on numerous further occasions due to storm damage, including its current incarnation in 1905. As the group approached Mount Stuart House we passed an ancient cedar of Lebanon (Cedrus libani) and Spanish chestnut (Castanea sativa) both planted in 1717. Other notable trees in the collection include the largest diameter Sargent’s rowan (Sorbus sargentii) and handkerchief tree (Davidia involucrata) in Scotland.
Beside a large cedar in the shadow of the grand house, Bartletts gave a demonstration of some of the methods being used as part of the tree restoration programme on the estate. Enriched biochar was scatted on the soil surface and compressed air from an air spade was used to incorporate it into the soil around the tree’s root system. This root zone invigoration programme improves the structure of the soil resulting in better water and nutrient retention as well as drainage. This in turn stimulates root growth, improving the vigour of the tree, and builds its natural resilience against pests and disease. The biochar will remain in the soil for hundreds of years after application and can stop the decline of trees.
Mount Stuart House. (Photo: Stewart Wardrop)
Up next was a stationary rope technique (SRT) tree climbing demonstration by climbers from Bartletts. The group was impressed by the speed that the climbers accessed the tree’s canopy and their use of redirects of the rope to get right out to the tips of branches. As well as improvements in speed, the SRT system reduces stress on the climber’s body which in turn should reduce injuries and prolong a climber’s career.
The final demonstration of the day was the Rinntech Arbotom sonic tomograph. Like other tomograph units available the system measures the speed of soundwaves through wood to map the internal structure of a tree and assess potential decay. Interestingly the system can also be used to map the roots of trees, making it a useful tool for arborists when assessing a tree’s stability or root protection area. The group then had a chance to continue wandering around the garden before those that needed to caught the ferry back to the mainland.
A big thank you to the Bute Estate for welcoming the Arboricultural Association to the island and showing us their incredible tree collection. Thanks also to Bartlett Tree Experts for a day of informative talks and demonstrations. Keep an eye on e-bulletins and the ‘Training and Events’ pages of the website for future branch events.
This article was taken form Issue 186 Autumn 2019 of the ARB Magazine, which is available to view free to members by simply logging in to the website and viewing your profile area.