Crathes Garden blog #9: American giants and English oaks

The native range of the giant sequoia (Sequoiadendron giganteum) is limited to groves on the western slopes of the Sierra Nevada in California – the groves extend to about 28,000 acres. One particular tree, known as General Sherman, is the most massive non-clonal tree on the planet. Its bulk easily surpasses that of a blue whale. [1] General Sherman is thought to be over 2,000 years old. [2] Such enormous trees sequester huge amounts of carbon.

Despite the fact that the wood is not of especially good quality, logging and clearing has diminished these groves to the extent that there is now real concern about their future. Giant sequoias have evolved to benefit from moderate fires: the spongy bark can cope with a certain amount of heat. Occasional fires burn off excessive debris, reducing the amount of fuel that might cause more intensive fires. These occasional fires result in small clearings for regeneration; the heat also helps to open the cones so that seeds can be released to germinate in the newly created ash that fertilises the forest floor. However, with the recent extreme weather events of the last two years, severe fires have killed many trees and their seeds. Increased erosion and drought has contributed to the environmental damage, thus further decreasing the likelihood of natural regeneration.

The giant sequoia quite likes the Scottish climate – the tallest specimen in the UK is to be found at Benmore (RBGE) in Argyll where the high rainfall suits it well. In the UK the trees are also known as Wellingtonias; in the USA as Washingtonias. Sequoias were first introduced in Britain in 1853, and there is some evidence to suggest that Crathes Castle and other Deeside estates were among the first recipients. [3] Many of those early plantings are still standing – sequoias rarely blow over because of their buttress-shaped trunks, but the shedding of side branches can be dangerous.

In the mid-19th century Robert Burnett, son of the 10th Baronet of Leys, was sheep-ranching in California following the gold rush. In 1859 he sent a parcel home to Crathes that contained the seeds of 13 different American conifers; these seeds would result in dramatic changes to the landscape of the estate.

As I approached the conifer glade, I could see that it had not suffered too much damage. However, to the north of the glade was a row of four ancient oaks; one lay sprawled across the ground. These four oaks are of the pedunculate or English oak species (Quercus robur) – so-called because it is more common in southern parts of Britain. Pedunculate oaks are easy to identify by their acorns with long stalks, compared to the shorter stalks of the sessile oak (Quercus petraea). The sessile oak also grows at Crathes and the two species are known to hybridise. Both species are excellent for biodiversity, providing a habitat for hundreds of different insect and bird species. A tree survey has estimated that at least two of these four oaks date to the 18th century, and they appear to be individually depicted on the first Ordnance Survey 25 inch to the mile map of Crathes (surveyed 1864–5 and published in 1866).

I took time to take in the damage, pondering on the amount of wood that remained even after all the twigs and smaller branches had already been removed. 300 years or more of life had come to an end. A couple of wrens chirruped about the fallen wood. Oddly, the fourth oak in the row has looked more than half-dead for a good while but is still standing. If you look carefully at the 2013 photograph above, you can just see the beefsteak fungus (Fistulina hepatica) at its base. This fungus causes brown rot in the tree, which is sometimes sought-after by furniture makers.

I wondered what it might have been like on the night of the storm for those living on the estate. Andy says he could feel his house vibrating as the wind took its toll. James had been away and arrived home in the middle of the storm, likening it to entering a war zone. He was unable to use the main drive due to fallen trees. He managed to get up Butler’s Avenue before the beech fell, but could see that the walnut had fallen. He was scared to look on the following day. He and Davy had to concentrate on clearing the roads for access, but he says it took him two or three days to digest the extent of the damage. James commented: ‘I am very reassured and proud of the Crathes team’s abilities and response in the clear-up operation given the level of destruction. The Brodie team were also excellent and saved us many weeks’ work with their generous help. For me, this underlines the importance for the National Trust for Scotland to ensure that we invest in these specialist skills within the organisation, not to mention the huge financial savings.’

In the 2013 photograph of the four oaks you can see the stump of the Lawson’s cypress (Chamaecyparis lawsoniana). This tree was one of the most successful of Robert’s seeds – an annotation on Robert’s list records that 42 were ‘very fine’. Because Lawson’s cypress was only introduced to Britain in 1854, no-one would have known how to grow it or what to expect of the mature tree. Hundreds of cultivars have been developed from the Lawson’s cypress, many of them dwarf forms that are now popular in small gardens. It’s likely that the Lawson’s cypress represented by the stump was one of those 1859 seeds sent from California. It was planted at the entrance to the glade but got damaged in an earlier storm. There is a replacement tree, but it will be many years before it looks proportionate to its opposite number – the western red cedar.

The western red cedar (Thuja plicata) is actually not a cedar at all; it is a cypress and looks very similar to Lawson’s cypress, although it smells more fruity, perhaps of pineapple. The specimen at the entrance to the glade has produced a small grove of trees by natural layering. This restricts the height of the mother. As I looked at the storm damage to one of the younger trees in the group, a small child ran past, calling to her friend that it is her favourite tree. The curved layering branches make wonderful places for children to play.

The first American giant to come to Crathes was the Douglas fir (Pseudotsuga menziesii), which had been recorded by Archibald Menzies and was introduced to the UK by David Douglas in 1827. It has been planted extensively on Deeside due to its impressive growth and valuable wood. There are quite a number of these firs at Crathes that must date from the 1850s or earlier. I was relieved to see that all of the major Douglas firs on the main drive and in the conifer glade are still standing. The noble fir (Abies procera), probably another of Robert’s trees, is also still standing proud.

I had seen from the drive that there were pockets of blown trees in different parts of the estate. As I walked beyond the conifer glade, I saw more individuals blown over. One fine oak tree had landed in the leaf mould heap.

Another day I looked around the viewpoint, admiring the young monkey puzzle and a lovely yellow witch hazel. Despite the mild weather, the Daphne bholua ‘Jacqueline Postill’ is not yet in flower, but the buds are ready to burst and will be making a fine show in the coming weeks. It was definitely flowering by mid-January in 2019. A red squirrel scurrying up a nearby tree made the day extra special. Red squirrels are fairly common at Crathes but they never fail to brighten up my day.

A new year, a new beginning? Well, not really as there is plenty of unfinished work due to the storms. There are, however, new and exciting projects ahead. Andy and volunteers Alyson and Sheila have been removing viburnums from the Rose Garden in preparation for the new design. A piece of the viburnum has been retained for replanting elsewhere. The Rose Garden project, funded by a generous benefactor, has been in the planning for some time; watch this space!

Updates

• Work has been going on in the Millpond. Working with the Dee Fisheries Trust, the pond is being surveyed prior to installation of new sluices. This will entail draining the pond for a short length of time.
• James and Steve have been working on the drain by the entrance building.
• Joanna has been cleaning and painting in the glasshouses.
• Almost all the trails are now open, but with some diversions in place.

[1] Some trees, like aspens, will sucker so that a whole wood may be the same organism. Giant sequoias sometimes layer but generally have a single trunk.

[2] The Archangel Ancient Tree Archive is a good source of information.

[3] See Susan Bennett, The Gardens and Landscape of Crathes Castle (Spey Books, 2019) for more information about the American conifers and their introduction to Crathes and Deeside.