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1 Jul 2024

The PLANTS project: Year Two findings

Written by Dr Colin McDowall, PLANTS Project Manager
A collage of images featuring various plants and people in navy blue uniform
The PLANTS project team have been working hard over the past two years
This month marks the second anniversary of the Trust‘s ambitious PLANTS project, which sets out to produce an inventory of the collection of plants held across our gardens. Two years in, here are some of our exciting findings.

The renowned botanist John Ray, visiting Scotland in 1662, was delighted to encounter species he had not seen before. He praised Edinburgh gardens and, when in Linlithgow, expressed surprise to see ‘divers [sic] exotic plants, more than one would hope to find in so northerly and cold a country.’ Like John Ray, our PLANTS teams have enjoyed exploring the diverse and sometimes exotic plants growing in Trust gardens right across the country. As we mark the second anniversary of the project, we have much to celebrate. For those of you who are new to the project, to put it simply, our aim is to inventory and document the extensive collection of plants held across Trust gardens and roll out a collection management database and procedure.

Why is the project necessary? Having complete and accurate plant records is crucial for arboreta, heritage sites and botanic gardens. By maintaining excellent plant records, the Trust can effectively care for its living collections and utilise them to support educational, conservation, research and aesthetic objectives. Many Trust gardens, like Branklyn Garden, have a rich history of managing plant records, with accession books dating back to the 1920s. However, each garden used different methods to track and preserve plant records, including handwritten index cards or books, maps and digital spreadsheets. The information collected and tracked by each garden also varied significantly. These challenges hinder the sharing of information between gardens and the ability to analyse and compare data on a national level.

Within this context, our three teams have successfully completed the audits of 23 out of the 35 gardens identified for the project (14 completed last summer and this spring alone). As mentioned in my last blog post, there have been many highlights, including the perfection of our techniques, some amazing plant discoveries, and working more closely with garden staff. Most of the data work is now complete for the 2023 cohort of gardens. The team spent a productive winter cleaning over 19,000 plant records and adding over 22,000 new accessions to the database, now at nearly 30,000 living accessions. During the year, three key themes have emerged.

Three people dressed in navy blue looking at rhododendron bushes
North team auditing rhododendrons

1) Living links to the past

Last year, we found that many of the plants we audited are valuable living links to the horticultural past of the gardens and their owners. Some of the gardens we visited in the last year have had owners famous for their plantsmanship, which remains a draw for visitors. However, for every Dorothy and John Renton (Branklyn) to Major Ian Brodie, 24th Laird (Brodie Castle) whose horticultural work was renowned in their lifetime, we have uncovered other owners and properties with lesser-known plant legacies. One owner of Geilston Garden (most likely when the Geils family [1805–1920] developed the walled garden) planted a wellingtonia (sequoiadendron giganteum) around 150 years ago. The Hon. Charles Leith-Hay and the Hon. Henrietta O’Neill extended the walled garden at Leith Hall and created the rock garden, which is now just over 100 years old and underwent a large restoration in 2020.

While at Priorwood Garden in Melrose, we discovered plants that the former owner (Mrs Jill Currie) cultivated for her interest in cut and dried flowers. A few hundred metres away at Harmony Garden, we learned the previous owner (Mrs Christian Pitman) was a lover of phlox, and the team discovered uncommon and rare-in-cultivation (difficult to buy) phlox originating from the well-known local nursery Forbes of Hawick. The nursery is no longer in existence, but in 1901 Forbes of Hawick had 350 named phloxes in their catalogue, and we felt like detectives as we worked to identify with the help of Colin Wren (Gardens & Designed Landscape Manager, Edinburgh & East) the Phlox paniculata cultivar ‘Dodo Hanbury-Forbes’ at the garden. This cultivar has had an RHS Award of Garden Merit, and its pink and peachy flowers are a different shade than any other border phlox. It is an old and rare-in-cultivation plant, and identifying it for preservation (for historical and horticultural merit) was a good example of the importance of our project.

A close-up of a cluster of small pink phlox flowers
Phlox paniculata ‘Dodo Hanbury-Forbes‘ in Harmony Garden | Image: Colin Wren

A garden I visited for the first time in the last year, and which has both historical and horticultural importance, was Falkland Palace. As a lover of history and gardens, I was enchanted by the 1950s design by Percy Cane, one of the best-known landscape designers in the UK in his day. Falkland is the only complete Percy Cane design in Scotland and was afire with colour and texture when I visited. The team were able to identify 44 mature shrubs dating from the Percy Cane planting, including fine specimens such as the beauty bush (Kolkwitzia amabilis) and lilac (Syringa vulgaris) ‘Andenken an Ludwig Späth‘. Rosa ‘Scharlachglut‘ also known as Scarlet Fire was a fine old specimen we encountered at Falkland. Records indicate it has been quietly flowering for decades.

We also identified some historic rhododendrons this year, such as R. ‘Ivery‘s Scarlet‘ at Arduaine Garden (dating from 1924), as well as over 34 rhododendrons dating from the 1920s and 1930s at Branklyn with wonderful cultivar names such as ‘Cynthia‘ and ‘Snow Queen’. At Crarae, we confirmed the existence of R. oreodoxa and R. augustinii, dating from the late 1930s and early 1940s. At Inverewe, we came across the Trust’s oldest rhododendrons in R. arboreum subsp. Zeylanicum (1906) and three Rhododendron 'Ima-shojo' Kurume (1907). At Inverewe, we have thus far audited 15 rhododendrons dating from 1900–30.

These historic plantings are important to the Trust, not only because mature specimens have a grandeur and beauty that awe visitors but also because they are valuable living links to the gardens‘ horticultural past and could play an integral role in ensuring that the genetic heritage of these plants is preserved for generations to come.

2) Discoveries of significant plant collections

Another discovery has been the scale of the plant collections within the Trust. Officially, our gardens are home to 17 National Plant Collections, from herbaceous perennials to shrubs, trees and bulbs. However, through our audit and the introduction of our new collection database, we can cross-search and analyse all the plants within the Trust’s care for the first time. For example, across all the properties audited to date, we have accessions for nearly 7,000 rhododendrons, over 3,400 daffodils (Narcissus), over 1,200 roses (Rosa) and nearly 800 geraniums. By analysing this data further, we have identified significant holdings of certain species in single gardens or across multiple properties.

Three people stand in a garden auditing plants
East Team and James Bell Head Gardener at Malleny auditing at Malleny Garden | Image: Colin McDowall

One example was identifying an unusual and important collection of lilies at Branklyn. Firstly, our project team came across a lily (Lilium superbum) which is believed to have been planted in 1928. Secondly, they found a significant holding of Lilium North Hybrids, also known as Mylnefield lilies. Their presence was known to the Trust as there was previously a well-known national collection of Mylnefield lilies at Branklyn. But it was pleasing to find so many still present in the garden. Their presence is fitting as Dr Christopher North bred the lilies a few miles away at the Scottish Crop Research Institute at Invergowrie in the 1960s and 70s. Bred specifically to tolerate the Scottish climate, they are not easily grown in the south of the UK, and a national collection is held nearby in Perth. The lilies come in various colours with some upward-facing flowers (due to their Asiatic parentage), while others have pendulous flowers indicative of their Martagon (Eurasian) parentage. Dr North named one series after Greek gods, and we found ‘Achilles’, ‘Eros’, ‘Minos’, ‘Odysseus’, ‘Orestes’ and ‘Pan’ at Branklyn, and ‘Ariadne’ at Crathes. Another series was named after Dr North’s family members and we found 10 of the 14 members at Branklyn. Both series of lilies are uncommonly found, and it is possible that some are already lost from general cultivation, which marks an important collection for future breeding and the history of local horticulture.

There can be few gardens that do not contain at least a few daffodils (Narcissus), famous for their longevity and for providing the first real splash of colour in spring. Therefore, it shouldn’t be surprising that we have now audited over 3,000 daffodils and over 500 named cultivars. In last year’s audit, a major collection of over 1,000 daffodils was audited at Greenbank Garden, along with the nearly 450 cultivars listed for Threave, including some rare ones. This year at House of the Binns, over 240 daffodils were recorded, including the cultivar ‘Elegance,’ listed on the 1916 RHS Daffodil Classification list as likely to be either lost in cultivation or surpassed by modern varieties. A mellow-yellow small cup daffodil, it was initially bred by Rev. Engleheart and remains rare. Earlier this year, ‘Elegance’ was entered in the Caledonian Horticultural Society Spring Show and won first prize!

A close-up of a single yellow daffodil growing outside.
Narcissus ‘Elegance‘ at House of the Binns | Image: Colin Wren

In the last year, we have also visited some of the Trust’s gardens which are internationally famous for their rhododendron collections (Arduaine, Branklyn, Crarae and Inverewe). I’ve been really taken by the rhododendrons we’ve seen: when in bloom, they are some of the most noticeable and beautiful flowers in the landscape. We have audited nearly 7,000 rhododendrons in the last two years, and with over 900 different taxa and over 500 registered cultivars, it is the largest and most diverse genus we’ve encountered. We identified an important collection of Kurume azaleas (azaleas belonging to the Rhododendron family but distinguish themselves from other rhododendrons by having five stamens (rather than 10+) and being deciduous or evergreen. In contrast, the rest of the genus is all evergreen). The noted plant explorer Ernest H Wilson made many expeditions to Japan in the 1900s and loved the evergreen azaleas from Kijiro Akashi’s nursery in Kurume. He imported to the UK what were, in his opinion, the best fifty azaleas, and gave them new English names. The ‘Wilson Fifty’ of Kurume azaleas are much prized in horticultural circles, and we have so far found six of them (‘Asa-gasumi’, ‘Azuma-kagami’, ‘Hatsu-giri’, ‘Ima-shojo’, ‘Kirin’ and ‘Kiritsubo’) at Arduaine, Branklyn, Crarae, Culzean and Inverewe. Today, the only known complete collections of the ‘Wilson Fifty’ are at the Punch Bowl and Valley Gardens at Windsor Great Park, at the Isabella Plantation in Richmond Park and in Exbury Gardens. Despite its name meaning ‘Christmas Cheer’ in Japanese, ‘Ima-shojo’ blooms in May. Three have been found at Inverewe that date from 1907 and were likely planted by Osgood Mackenzie himself.

3) Rare and unusual plants

Of the 1,157 rhododendrons published in 2011 by the International Union for Conservation of Nature (IUCN) Red List book of rhododendrons (Critically Endangered, Endangered, and Vulnerable), 316 species are noted as ‘threatened with extinction in the wild’. The PLANTS project has found that the Trust holds 120 of these critically endangered, endangered and vulnerable species. The west coast garden of Arduaine has 68, with 27 requiring expert identification to confirm their presence. Included within this number from the IUCN Rhododendron Red List are Rhododendron amesiae (a rare shrub only known from 2 or 3 locations in China) and Rhododendron cinnabarinum subsp. tamaense, vulnerable to extinction in the wild and found in the wild just one locality in China and two in Myanmar. This information came from 2011, so the true figure will likely be worse.

Eighteen ‘critically endangered‘, ‘endangered‘ and ‘vulnerable‘ (according to the 2011 report) rhododendron species were identified at Crarae, with 15 needing further identification. Rhododendron coriaceum was one of the ‘vulnerable in the wild‘ species and is an important part of the garden‘s history. It was planted in 1922 and originated from J B Stevenson of Tower Court, a famous turn-of-the-century rhododendron grower, who sponsored explorers including Fortune, Wilson, Farrer, Forrest, Kingdon Ward, Ludlow and Sherriff. His own collection was dispersed after his death and many of the best specimens went to Windsor Great Park. It is exciting to be able to trace the plant‘s lineage back over 100 years. The importance of this species and its historic provenance were unknown to the garden team at Crarae, and it is now earmarked for propagation. This highlights the importance of species identification to allow for meaningful conservation management.

Among others on the IUCN’s critically endangered list for trees, we have identified Abies nebrodensis (native to Sicily where the population consists of only 30 plants) growing at Crathes. Also recorded at Crathes is Pyrus korshinskyi, a wild species of pear tree native to Kyrghystan, Tajkistan and Uzebkistan. Finally, at Arduaine we found the quite rare-in-cultivation Glyptostrobus pensilis (Chinese swamp cypress); its feathery foliage is unusual in conifers. More research is needed, but so far 36 species of tree have been found in Trust gardens that are on the IUCN red list status.

Two years into the project, I am pleased to say that we are fulfilling our objectives and are on track to finish on time. As always, I have been impressed by the breadth of horticultural knowledge and diligence displayed by the team. I hope I have demonstrated that the team has made some incredible discoveries thus far: plants that reflect their garden’s unique history, plants that form unique collections, and rare and endangered plants. This points to the potential that our project has for the future. This research will allow the Trust to help gardeners prioritise their sourcing and propagation. It will also cement the Trust’s position as a unique resource for people searching for plants. We can’t wait to see what other discoveries we will find across the Trust as the summer unfolds!

Plant Listing at the National Trust for Scotland (PLANTS) is the biggest horticultural audit project undertaken by the Trust and aims to celebrate, protect and better understand the flora and vegetation across our gardens and designed landscapes.

Read more about the PLANTS project

This project has been made possible through the generous support of the Row Fogo Charitable Trust.

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