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20 Sep 2021

Crathes Garden blog #5: it’s all in the genes

Written by Susan Bennett, garden guide at Crathes Castle, Garden & Estate
A man stands on the platform of a cherry picker-type piece of machinery in order to cut a large hedge. He uses a long-handled hedge trimmer.
Mike cutting the hedge at Crathes Castle Garden
Over the next few months, our expert garden guide is sharing a blog offering a behind-the-scenes look at what the team are working on in the garden at Crathes. Here is Susan’s entry from September, where she shares some of her research about the much-loved yew trees:

As August turns to September, we enjoy the hot colours of summer: the tiger lilies; the red dahlias; the orange heleniums; the many salvias; and – new to the garden – the little bat-faced cuphea (Cuphea llavea ‘Torpedo’), which makes a low mound of bright red and purple flowers. The cuphea is a native of Mexico and its long, purple, hairy calyx and corolla tube gives a clue to its main pollinator – the hummingbird. Whilst there are no pollinators with long enough tongues to do the job in Scotland, the bees have bored holes in the bottom of the calyx and the corolla tubes here and enjoyed the nectar. The two red petals give the plant its comical name.

For the gardeners at Crathes Castle, August is dominated by the cutting of the yew hedges. Nowadays it is facilitated by a mobile elevating work platform (MEWP). Mike and Steve are the main hedge cutters and they need to make good use of the MEWP because it’s expensive to hire. However, this year it broke down and for a while things slowed up and ladders were used as they were in the past. But not shears! The cutters are electric, which have the added advantages of being quieter than the previous cutters and being more planet-friendly; the MEWP is noisy and still runs on diesel.

A man stands on a tall ladder next to a cone-shaped section of hedge. He uses an electric strimmer to shape it.
Mike doesn’t have to lean the ladder on the topiary; modern ladders are safer and kinder to the hedges.

Some of the hedges were not cut last year and the Scottish flame flower (Tropaeolum speciosum) has become even more of a nuisance than usual. We have a love/hate relationship with this Chilean nasturtium – it’s definitely part of the Crathes summer scene, but rather a trial when it has to be removed before cutting the hedges. By the beginning of September the walled garden yews are just about finished, but there are still hedges and bushes to cut elsewhere – some around the nursery area and some at the West Lodge.

The ‘egg and eggcup’ yew topiaries are thought to have been planted in 1702. They are much loved by visitors – they have that ‘wow’ factor that makes a visit memorable. They also have relevance in a national and international context. The Royal Botanic Garden Edinburgh (RBGE) is an important player in global conservation and one of the remits of the garden is to preserve the genetic diversity of species wherever possible. Diversity is best preserved in healthy habitats and ecosystems, but with the planet in crisis there is an urgent need for conservation in seedbanks and in living collections.

Two topiary yew hedges, shaped like an egg sitting in an eggcup, stand either side of a small garden gate. The pink walls of Crathes Castle can be seen in the background.
The ‘Egg and Eggcups’ before the cut

A project started some years ago, the International Conifer Conservation Programme (ICCP) is slowly coming to fruition at RBGE with the planting of hundreds of yew trees (Taxus baccata) from diverse genetic origins, in the form of the new perimeter hedge. A cutting taken from the famous Fortingall yew in Perthshire began the planting in 2014; eventually around 2,000 yews will be planted. When complete, the hedge will contain cuttings from 17 Scottish heritage yews; from 18 English, Welsh and Northern Irish yews; and from 2 in the Republic of Ireland. It will also contain plants grown from seed collected from various locations within the natural range of the yew, including two English sites and one Republic of Ireland site, as well as Denmark, Albania and Croatia. A heritage hedge can successfully preserve a wide genetic diversity of one species in a relatively small space. In this case 30% of the cuttings are from Britain and 70% are from other countries.

Why is this hedge important? With such a depletion of the natural habitats of yews, the possibility of declining health – in the way that human inbreeding is detrimental – might affect the long-term future of these trees. If we learn to manage our resources more effectively, habitats may be restored and the diversity of the RBGE hedge will give any such restorations a greater chance of success.

Yew trees grow in a dark, craggy woodland.
Yews on the crags to the south-west of Crathes Castle

The Crathes ‘egg and eggcups’ are over 300 years old, and a cutting from the more southerly topiary has been included in the RBGE hedge. Also included is a cutting from one of the yews that grows near the crags just to the south-west of the castle – thought to have been planted around the end of the 18th century.

I was delighted to realise that I was familiar with some of the other yews that are represented in the hedge. The Fortingall yew, sometimes said to be 5,000 years old, is estimated by RBGE to be between 1,500–3,000 years old and may be the oldest tree in Europe. It’s a long time since I was there – before the days of digital images. For centuries, this yew has been a tourist attraction; its surrounding wall dates from the late 18th century. The Selborne yew and the Kingley Vale yew wood were seen when we spent a holiday in the South Downs in 2015. A highlight (there were many) of that holiday was a day spent visiting the garden of Gilbert White, the famous naturalist (1720–93), who lived in Selborne. In the churchyard at Selborne I was fascinated by the enormous stump of the ancient yew which had blown down on 25 January 1990. The tree was torn up in the gale and it was decided to cut the crown back and replant the massive stump. Cuttings were taken at the time and one is now successfully growing in the churchyard, but the parent tree was later pronounced dead. It appeared to re-sprout in 2008, but it is thought that the sprouts are seedlings, not clones of the parent tree. The Kingley Vale yew wood is just to the north of Chichester – this is the largest yew woodland in the British Isles.

A very large stump of an old yew tree stands beside an old church wall. The stump is covered in climbing plants like honeysuckle and ivy. There is a plaque on the ground in front of it.
The stump of the Selborne yew, July 2015

Yews are dioecious – male and female cones grow on separate trees – although trees do sometimes change sex. The single seed is surrounded by a red fleshy scale, which looks more like a berry than a cone. The Fortingall yew is male but recently developed a branch that is female.

Some of the yews at Crathes are Irish fastigiated yews – growing tall and straight – and I was interested to see that cuttings of the Florence Court Irish yew in Enniskillen have been incorporated in the heritage hedge. The story of the Florence Court yew dates back to 1767 when a local farmer, George Willis, collected two saplings from a nearby mountain. He gave one to Florence Court; the other, which he planted in his garden, later died. The Florence Court yew – a female – thrived, and many cuttings were taken. All the Irish yews in the world are thought to have originated from this one tree. Any seedlings derived from the berries revert to normal spreading growth; the cuttings preserve the genetics.

A close-up view of a section of an Irish yew tree, whose branches grow pointing straight up towards the sky.
The uncut top half of this Irish yew at Crathes shows the fastigiated upward growth.

I did wonder if the Hampton Court yews might be incorporated in the hedge, but no. However, I can’t resist including them in my reminiscing about yew trees. They had been planted as avenues in the Great Fountain Garden created for William and Mary, about the same time as the ‘egg and eggcups’ were planted at Crathes. The story goes that, later, Lancelot Brown (c1716–83), famous for developing the English Landscape tradition, allowed the yews to grow naturally. I love their now-clipped, unusual shapes.

Martin Gardner, Co-ordinator of the ICCP, has given me information on the RBGE hedge. [1] He says they are now planting the last part of the hedge with trees he collected in Morocco some years ago. Martin is writing a book about the hedge, which will include information on each yew from which they collected material.

The yews at the north end of the Crathes Millpond were probably planted in 1858, when the millpond was developed into a decorative feature as the East (main) Drive was established. Before that, the millpond had been purely functional and part of the Candieshill rental. When I was nosing about around the yews at the millpond, I saw some interesting fungi. The white fungi seemed to sprout where broadleaved tree trunks were lying rotting – often following the line of the trunk. Less welcome was the sight of the invasive skunk cabbage; there was more along the side of the Coy Burn.

The rain following the heat has brought forth a crop of different fungi. There are few species that I am confident to identify, but I find them beautiful and intriguing so will just post a few photographs:

Genetics came up again when I was talking to Joanna about the Aeonium tabuliforme that is flowering in the broadspan greenhouse. This plant is fasciated – ‘when several contiguous parts grow unnaturally together into one’ (Oxford English Dictionary). I remembered that when the original plants flowered, one of them was fasciated. So we wondered if some of our collected seed had originated either from the fasciated plant or from seeds pollinated by the fasciated plant. An online article suggested fasciation can be caused by recessive genes. [2]

A bright green aeonium plant grows in a plant pot. Its base appears to be made up of several large branches, all melded together.
Fasciated Aeonium tabuliforme

My computer auto-corrected fasciated to fascinated; checking on the spellings and usage of both fasciated and fastigiated I realised that I had often mixed them up and used them incorrectly. Since we have plants of both types in the garden, I soon had the words sorted out. The Dawyck beech that grows in the Golden Garden is a good example of a fastigiated plant: its branches, like the Irish yews, all grow upwards. It was found around the mid-19th century in the grounds of the Dawyck Estate, near Peebles (now belonging to RBGE). It was moved nearer to the house and a later owner dispersed cuttings to the botanical world.

More issues of genetics arise as we contemplate the Portugal laurel in the centre of the White Border. We don’t know its age, but it’s well over 100, perhaps 200 years old. For some time the head gardeners have worried about it. Now hollow and looking rather thin on top, the time to replace this laurel cannot be that far away. The regrowth at the bottom shows us that it would not die if the top was blown over, but its position in the garden calls for a more immediate solution.

Many years ago, a new plant was raised from a cutting of this tree and was planted in the gardener’s garden until such time as it was needed. However, the years went by and the young tree is now too big to transplant. Another solution awaits in the yard thanks to the cuttings that Joanna took in 2019 having grown amazingly. True, they could do with being a little bigger, but should there be an emergency the new cutting, which will have the same genetics as the old tree, could easily take its place.

A collection of saplings in large plant pots stand outside a glasshouse in a walled garden.
Cuttings taken in 2019 are being trained to replace Portugal laurels in the Walled Garden

Updates

  • Work continued on the drains, with James and Davy shifting about 40 tonnes of hardcore to improve the camber on the path to the garden. Larger drains and silt traps are also to be installed and it’s hoped that the long-term problems of flooding at the gate will be sorted. In the garden there has been a concentrated effort to improve the paths.
  • At last we have some butterflies, with peacocks enjoying the buddleias. It has been a worrying year for insects, with few of the usual solitary bees in evidence.
  • There is definitely a feeling of autumn in the air now and the plants confirm the turning of the year. Autumn crocuses and nerines are in flower; the crab apples are making a show; and viburnum and enkianthus berries are ripening, as are the conkers on the horse chestnut trees.
A close-up view of some purple and yellow autumn-flowering crocuses growing on a woodland floor.
Autumn crocuses are popular with the hoverflies.

[1] ‘Conservation Hedges – Modern-Day Arks’ in Sibbaldia (Journal of Botanic Horticulture) No. 17, pp. 71–100

[2] Annals of Botany, vol. 98 (4), October 2006, pp. 715–730