‘Westonbirt – Care of The National Arboretum’ A webinar reviewed by Mark Chester
By Mark Chester
2021-04-19
The event was introduced by John Parker, who was the host. He introduced the panel of Andy Bryce, who is the Collections Manager, Penny Jones who leads on propagation, Michal Dvorak, dendrologist, and Alison Vry, Plant Records Officer.
Andy began the presentation by sharing the history of the arboretum. Its existence is due to the efforts of the Holford family. George Holford inherited the estate in 1839, which was much larger than today, and included Westonbirt House, the family home. Plantings had begun in the 1820s, and George worked with his son, Robert, to develop collections from around the globe. Robert took on ownership in 1892 when George died. Plants were chosen for their aesthetics, not botanical attributes. Many of the trees from this period remain, includes an Acer griseum.
Badger activity during this period proved serendipitous. The badgers dug setts, bringing soil to the surface highlighting variations in the soil and allowing trees and shrubs with different requirements, to be planted. This has included Rhododendron. The Acer glade was planted and photographs of it were used for stamps to commemorate the centenary of the Forestry Commission.
Sadly, Robert had no children and the estate passed to his nephew Lord Morley. Morley lacked the passion of his uncle and the estate was split up. The arboretum began to decline and when he died in 1957, it passed in the Forestry Commission in lieu of death duties. A decision needed to be made: should the FC retain the collection and restore it, or fell the trees present and plant with Spruce. The committee met, and anecdotally was undecided. At the vote, the Chair had the casting vote. He voted to restore. An asset has been saved!
Today, the site covers 630 acres and is home to 15,000 specimens. These cover 2793 taxa with some 135 champion trees and 113 red data trees present. There are 5 National Collections.
In addition, there are 1400 species of fungi, 500 moth species have been recorded, 20 butterfly species and 12 bat species…..
As Andy brought his History of the Arboretum to a close, he shared that the arboretum is managed as a tree collection, also an ecosystem with the challenges this presents. It is also a Historic Park and Gardens, listed landscape, research and plant health station, and a place which attracted more than 550,000 visitors in 2019.
He concluded with a comment on his own journey. He decided early in his career that he did not wish to prune conifers for the rest of his life so began to study, actually taking his Professional Diploma at Westonbirt 15 years ago. He joined the team 10 years ago, and clearly relishes the role and the challenge.
Penny Jones is the Plant Propagator. She spoke about succession planning. The nursery at Westonbirt is small, with just three glasshouses and 2 tunnels. Most trees are propagated from seed and the focus is to increase the species present. Some trees are propagated to increase the population and others to replace existing specimens, this being particularly challenging.
She shared the five key aims of the Arboretum: to maintain and develop the collection, to provide opportunities to learn about trees, to maintain the arboretum as a healthy resource, to protect the heritage and to create a diverse community.
For selection of trees to propagate, she shared that the criteria applied are to assess the heritage value of the tree, its landscape value, to manage the national collections, to promote education and learning, to enhance and support science and research and to support conservation.
There is also a need for continuity. Just 21 species of signature plants are widely used across the site. The National Collections include two genera of Acer and one of Tilia.
The arboretum is also recognised for helping mental health, and being part of Forestry England, it has links to Forest Research. This enables an annual check for pests and diseases.
Michal Dvorak began his talk by asking why does correct identification matter. He explained it is needed to verify the collection and to ensure that changes to taxonomy are implemented. He also works closely with Penny to identify new trees to propagate and with Alison, the Database Officer to ensure the database is correct.
His work has three aspects: to confirm the accuracy of the existing name, to identify unknown trees and to confirm that the name selected is value. This is needed for planning, for research and for trials. It is also important for pathogen tolerance.
There is a need for accuracy. At Westonbirt, 22% of the trees have been verified, compared to the Bedgby Pinetum with 5.6% accuracy and 30% at RBG Edinburgh.
Alison Vry shared about her work as the Plants Records Officer. For ease of management, the site has been divided in to 60 sections.
Andy then shared about the work of managing the site. When the arboretum was being established, the Holborns could employ as many staff as they wished. Today, he has access to just six arborists and two trainees. They are led by Richard Townsend, who has been at Westonbirt for 32 years. Continuity is important. Most of the work is done in-house, which enables the team to be more informed when carrying out establishment checks and to monitor growth and undertake timely pruning.
He acknowledged that the team is about a decade behind on their programme of work. The priority is to keep trees as they grow, or to fell if views are being affected. Tree safety is an issue, although fungi is not necessarily an issue. Indeed, a decaying tree is only felled if injury or damage is an issue.
There are three zones, 1, 2 and 3. Zone 1 is annual inspection, zone 2 is inspection on a 5 year rolling programme. Zone 3 is no formal inspection. Trees with known defects are inspected annually.
One of the challenges Andy and his team face is dismantling large trees. Only 3 arborists are used for these, enabling a high standard of training but also ensuring that the workload is spread.
One of the recent developments at Westonbirt has been a system to process mulch. Mulch is stored in bays and turned to keep the heat. It is then used across the site. The major benefit is that pathogens that may have been present are killed off.
We then had a time of Q&A. John, our host, observed that some 50 questions had been submitted, which was a record for a webinar. Penny was asked if there is potential for more nursery space. This might happen in the future…..
Michal was asked what process is used for validation for dendrology, and could this include DNA. He makes extensive use of books, photography, and DNA.
Alison was asked about specific areas to visit on a day trip. There are seasonal routes, but it is possible to visit most of the site in a full day.
Andy was asked if there is a problem with labels being damaged and how are they fixed to trees. Nylon screws are used because they don’t damage chainsaws.
Is squirrel damage an issue? It is, with no control at present.
Penny was asked whether offspring of champion trees are champions. She explained that the nursery does not propagate by grafting, and seeds may not be true to type, so no champion trees have been propagated.
The team was asked about opportunities to learn from shadowing. There is limited opportunity but tours are provided.
Is it hard to inspect trees with so many visitors? No. The team just walks around inspecting trees. They may get some strange looks….
Penny was asked if she has any species on her most wanted list. She does, including Maples and other Acers.
What is the tallest tree on the site? It is an Abies grandies at 43.5m.
The oldest is officially the 1000 year-old Lime, which is a coppice. There is an oak in the old arboretum from 1600. The Holfords planted a Scots Pine in 1829.
Are visitor numbers increasing? Yes.
Is there much engagement with visitors? Yes
Is there an issue of compaction from visitors? Visitors usually stay on paths.
Who has the final say on felling trees? Andy identifies possible trees with the team, and they have discussions about how to proceed. The decision is taken with careful consideration.
Who has the say about allocating new names to trees? Michal….the approach is that a name is right until it is shown to be wrong!
The team were asked to name their favourite tree. Penny has a tree in the Styraccea family, Michal has Abies procera; he likes the silver foliage. Alison likes Picea almonza
Finally, they were asked to name their favourite tree book:
Penny: Seeds of Woody Plants in North America
Michal: New Trees by Bryton and Grimshaw
Penny: A Plantsman’s Paradise-Travels in China by Roy Lancaster
Andy: Meetings with Remarkable Trees by Thomas Packenham. It includes some trees at Westonbirt. He shared that Thomas visited Westonbirt recently, which was a special moment.
The event ended at 8pm. John commented that more than 550 people were present at the start, including delegates from as far as Israel. Shortly before the close, more than 200 were still present. It was a great evening.