Espaliered pear trees against a breathing retaining wall

My visit to Chambord Symposium in June 2022 helped me to plan a tree-planting project in more details, in response to a civic plan to refurbish the retaining wall of my garden. Innovative solutions might be needed to make the wall safer while still allowing it to release moisture and capture heat.

In December 2021, I inherited the house where I grew up in Aurillac. The property, owned by my family since the end of the 19th century, includes a listed garden. I intend to rejuvenate the garden, which has suffered decades of neglect.  

Fruit trees used to grow in this south-facing walled garden. When I was a child, espaliered pear trees grew up against the big wall. I remember the wires guiding their branches, the lizards sunbathing next to them. I can still hear the sand falling from the crumbling mortar that joined the stones as the little reptiles ran after each other or swiftly climbed for safety behind the leaves when I tried to catch them. Vegetables were also grown in this garden, at an even earlier time.

As soon as I was made aware of plans to strengthen the retaining wall which separates my property from the adjacent premises of a public high school, I started to research how this refurbishment could be made compatible with my project to recreate a kitchen garden.

Observing and taking pictures

I examined the wall closely. Below are pictures I took mid-June to illustrate my wish to keep it breathing. This solution would give the best chance for the kitchen garden to thrive. It would also allow for the well-designed conservation of a listed place, giving it additional meaning in the context of renewed public interest in urban agriculture.

A picture of my garden
My urban garden. We can clearly see two of its three terraces. At the top of the picture, the retaining wall. To the right, below the third terrace, sits a well, filled with 8m3 of spring water. Photo 17 June 2022, Aurillac, France.
A picture of an old nail in the wall
An old nail and some wire, aimed at guiding espaliered trees against the retaining wall. This is evidence of the garden’s past I would like to keep on site. Photo 18 June 2022.
A picture of two lizards on the wall
The lizards are still there, which contribute to the biodiversity and the balance of the garden’s ecosystem along the wall. Photo 14 June 2022.
A picture of an arch in the wall
This arch at the bottom of the wall has always puzzled me. An interesting piece of heritage?
A picture of a thermometer on the wall
At 10am on this mid-June day, the temperature has already reached 42°C (108°F) in the sun. Global warming won’t make things better. Fortunately, the breathing wall allows for humidity and heat regulation, which is good for the garden. Photo 18 June 2022.
A picture of a weep hole in the wall
The wall ‘perspires’1 thanks to the porous mortar used when it was refurbished and heightened at the beginning of the 20th century as part of the construction of a building on the land above. Decade after decade the mortar crumbled, giving way to deeper gaps between the stones. The retaining wall, exuding moisture from the mound behind, prevents excessive dehydration from occurring in the garden. Weep holes also allow for excessive humidity to be evacuated. The weep hole to the top right of the picture is 90cm deep. This breathing probably also brings some freshness in summer. Photo 14 June 2022.
A picture of the dark stones
The first 50 to 70cm suggest that the basis had been kept as a dry-stone wall, which enables it to breathe even better. The dark stones also store heat during the day and release it overnight. It significantly contributes to regulating temperature, which is not only useful during summer heat waves but also in spring, where it limits the risk of late frost and the consecutive loss of the year’s crop. Photo 18 June 2022.

Additional elements collected at the Chambord Symposium

More than a hundred experts from six countries met at Chambord Castle in France on 23 June 20222 to discuss the conservation of historic kitchen gardens. Garden historians, landscape architects, owners of heritage properties, curators of public parks and gardens, head gardeners, experts of fruit trees and other participants such as myself met for the first time in person after two years of online conversations launched at the initiative of the UK’s Walled Kitchen Gardens Network3 and the French Association des Amis du Potager du Roi4. We visited three historic gardens the following day.

A group of participants to the symposium standing in front of a stone wall with espaliered fruit trees
In conversation about espaliered fruit trees during our garden visits. Photo J. Cattaneo, 24 June 2022, Villandry Castle, France.

I took advantage of this symposium to search for information relevant to the rejuvenation of my garden. Here are my main findings.

Retaining wall

Specific mortars allow for walls to breathe. A technical expert and former curator of the fruit tree collections at the Potager du Roi told me that it was a good idea to keep dry stone at the basis of the wall and to use perspirant mortar above. He also said that adding particular components to the mortar helps grow fruit. He mentioned common practices such as adding crushed brick to capture the heat of the sun and charcoal which has antifungal properties. Further research into perspirant mortars would be required to choose the best option for the retaining wall in my garden.

A picture of a retaining wall at Villandry
Old retaining wall made of stones jointed with mortar. Photo 24 June 2022, Villandry Castle, France.

The main function of a retaining wall is obviously to retain the mound behind. It should be solid enough not to collapse. We didn’t discuss this at the symposium as it was out of topic. Having said that, I came across a consolidated wall in Villandry which made me think about the big wall in my garden and the plan to make it safer. I have since read the safety diagnostic carried out ahead of this plan. Would a classical solution consisting in repointing joints with perspirant mortar and adding x-shaped crosses be satisfactory? Maybe not, even if the wall above my garden doesn’t look deformed, contrary to the one I saw at Villandry. More innovative solutions to secure this wall while keeping it breathing might have to be considered.

A picture of another retaining wall at Villandry
This wall was clearly deformed at the top. The cast or wrought iron crosses used to consolidate it were of an unusual but aesthetically interesting shape.

Espaliered trees

The former curator of the fruit tree collections at the Potager du Roi told me that my ancestors made the right choice in planting pear trees against our south-facing wall, as they require a lot of sun to thrive. Apple trees are better placed against walls that are less exposed to sunlight. My initial intention to follow in my ancestors’ footsteps and replant espaliered pear trees against the retaining wall has therefore been confirmed as the right thing to do.

The technical experts present at the Chambord symposium discussed the question of excellence in gardening practice and fruit tree training at length during our Friday’s garden visits. They used the fruit trees at hand to evidence and support their views in a concrete and practical way. I came to three conclusions for my garden.

Firstly, fruit trees are very specifically trained in prestigious historic kitchen gardens. They require a lot of care from expert gardeners, who not only apply their skills but also experiment with them to advance their already very elaborate techniques. What is put on show in these gardens is the excellence of their abilities, evidenced through trees strictly shaped which produce the best and loveliest fruit. My aim is different. I want to recreate a relatively low maintenance domestic kitchen garden that can be easily passed on to the next generation. Less precise shaping and more occasional care will make the trees look less groomed but will be more in line with what an amateur gardener can do.

A picture of two experts touching an espaliered pear tree at Villandry while discussing fruit tree training
A German technical expert in trained trees detailing to a British senior gardener the multitude of operations he carries out every year to reach the best outcome.

Secondly, the experts pointed at some trees which were showing signs of weakness, highlighting why and what should be done in such cases. One of the reasons was that dwarf trees are more difficult to grow and require more care. I am now planning to plant more vigorous semi-dwarf trees as espaliers. In fact, they will resemble the old ones who grew there when I was a child, bigger and less trained than most of their prestigious historic kitchen gardens cousins.

A picture of a dwarf espaliered pear tree at Villandry
Strictly trained dwarf trees require a lot of care.

Thirdly, I am going to follow the trend highlighted by the owner of a Belgian nursery which specialises in trained fruit trees. She mentioned that gardeners tend to leave more space between the espaliered trees and the walls now than before. I have enough space in my garden to do so, and this will contribute to optimising the conditions for the trees to flourish against the breathing wall.

A picture of the space between the espaliered pear tree and the wall
Unlike these, the espaliered trees in my childhood garden were planted very close to the wall.

In conclusion, there is room in my property for recreating a garden that will both testify of its past and show what we can do today to reduce our carbon footprint through domestic kitchen gardening. In this particular site, it might require to develop innovative solutions for the retaining wall to be both safe and breathing. I believe it is a challenge worth taking up which can only benefit all the partners who get involved in it.

A picture of old ans news nails next to each other on a wall at Villandry's castle
Old and new nails next to each other above the roses on this wall at Villandry. It would be great to keep the old nails in place in my garden, however it might not be possible as part of an innovative solution which makes the retaining wall both safe and breathing.

To be continued.

References: (accessed 25 July 2022)

  1. https://lamaisonnature.ch/les-materiaux/mursperspirants/ (in French)
  2. http://europeangardens.eu/en/events/event/8761/ (scroll down to find the presentation of the event in English)
  3. https://www.walledgardens.net/about-us/
  4. http://www.amisdupotagerduroi.org (in French)

2 thoughts on “Espaliered pear trees against a breathing retaining wall

  1. Intéressant; Paresseusement j’ai planté des poiriers ordinaires à 75 cm du mur; Cette solution dégradée est-elle un moindre mal ?

    • Bonjour Pierre,
      75 cm, une distance supérieure à celle qu’on peut voir sur la photo des poiriers palissés de Villandry, me paraît bien pour des poiriers “ordinaires”. Qu’ordinaire signifie poirier de haute tige ou semi nain. Si vous les avez plantés récemment, il faut les arroser cet été, à raison je dirais de 20 à 40 litres d’eau en une fois tous les quinze jours. La recommandation du Urban Orchard Project est de 20 litres l’été pendant les trois premières années, mais le climat n’est pas le même et je tiendrais compte de l’exposition du mur. Il serait également bon de les tailler en février-mars pour les former, quelque soit la forme que vous souhaitez leur donner, afin d’obtenir à terme quatre ou cinq branches principales, que l’on appelle charpentières. Amitiés, Jean-Jacques

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