During February we built two retaining walls on the Woodland Banks in Lady Anne's Garden. The reason was to create a terraced effect, providing planting pockets and a less severe incline to work on when tending the plants. The walls and terraced effect also work further to blur the boundary between the garden and the woodlands above.
The first step before building could take place was to erect a line to indicate the final curve and level of the wall. The finished level of the wall and the earth it was retaining was particularly important in this situation due to the presence of a tree, Prunus verecunda
'Autumn Glory' AGM.
The final soil level could not afford to be above the tree’s root flare level as this would be detrimental to its health.
The next job was to dig down to the subsoil layer for placing the large footing stones. A problem I encountered when digging the footings was the presence of roots belonging to the Prunus
(cherry) mentioned earlier. Damaging Prunus
in the winter increases the risk of infection from the fungus silver leaf
, causing branches to die back. The fungus releases its spores in autumn and winter and enters its hosts through damage or pruning cuts. To avoid damaging these roots, stones were placed on either side leaving enough space for the root to increase in size. These stones were then bridged with a large stone over the top.
Smaller stones were then placed on top of the footing stones ensuring to always bridge the two stones below. A good tight fit with weight resting on both stones underneath it, pinning them down, is required. If the stone has any movement a smaller stone should be used to chock it always from the back of the wall. Subsoil can then be packed in behind and occasional larger stones added to hold everything in place and key the wall back in to the bank behind.
Finally, once the wall was built, a generous layer of compost was spread over the new incline to improve the ground ready for new plantings.
This area is well worth a look, (not just for my wall), in the coming months as the plants here, such as camellias and rhododendrons come in to their own.