In the spring of 2016, GFAA undertook a significant project to level an area at the lower part of the site, and install additional drainage to improve management of surplus rainwater. The project raised a low-level section of road, marked the Primary School plot with sleepers, and levelled the area between the raised beds and the Primary School plot to enable the future installation of a shelter with wheelchair access, and further raised beds (future). This area has since been sown with grass. Surplus soil was banked against the south wall of the site (forming the “South Bank”, between the row of alternating mature lime and sycamore trees.
In the immediate term, our approach to managing the South Bank had the following stages:
GFAA Committee asked Michael and Marion Hart in March to review the RHS guidance for grass or meadow flowers for the “South Bank”, as weeds had not yet propagated on the newly moved soil.
In practice, RHS guidance for long-term cover of shaded slopes does not include meadow flowers, and grassing steep banks presents a challenge for maintenance (strimming) of the slope. RHS priority actions focus on stabilization of the bank, and weed suppression; plants can be planted through coconut mesh deployed to stabilize the slope, the mesh degrading after around 6 years. Plantings suggested are a range of evergreen shrubs and evergreen or deciduous ground cover. Meadow flowers are less preferred under trees, where the slope is not otherwise stable, little sun is available to germinate seeds and rain damage is concentrated under trees.
Particular challenges of the slope included very limited sun, shade by trees from both light and rain. Excess soil should be removed from the base of trees. Planting should be unattractive to deer and rabbit, but low maintenance. Formal ground cover planting at recommended spacing would be expensive: the committee accepted that plotters should be canvassed for their views/available plants, and that an initial zero budget approach should be taken.
In addition to selecting plants to stabilise the bank from soil movement, a number of additional activities were necessary to prepare South Bank for its proposed low-maintenance life.
During the relocation of soil to the South Bank, two tree trunks were covered with soil above 12″ from the previous ground level. While the trees are mature and might be robust enough to incur little damage, the decision was taken to uncover the base of the trunks as far as practicable without damaging the bark.
Soil movement into the gulley will be monitored in case further action (e.g. shallow wooden roll support) is required to protect the trunks.
The soil which was removed to the South Bank was the balance of a load of 1000 tonnes donated by Barratt Houses, and contained substantial amounts of stone. Piles of larger stones taken from the surface of the South Bank were moved by trailer to stabilise access to the bins beside the main car park, where the temporary accumulation of water had made the ground soft and difficult for deliveries of chips and leaves.
Some stones remain on or near the South Bank surface, and will be collected as the bank is stabilised by planting.
The soil which has been banked up had been occasionally sprayed to inhibit weed growth, but still contained a variety of perennial weeds. In early 2016, creeping buttercup, dock, couch, nettle and rose-bay willow-herb were readily found, and have been removed before and during planting sessions. Creeping buttercup is the most prolific and likely to be the most persistent, particularly on the top of the bank. A further programme of eradication is likely in late 2016.
Soil quality is similar to the soil contained in the Primary School Plot. It dries readily and readily supports weed germination. As with the Primary School Plot, additional organic matter may be beneficial (i) for planting in sockets in the bank (ii) generally to encourage moisture retention.
Plant offers and planted
Plotters responded well to an email request for spare shade-tolerant / ground cover plants. Early planting included a string of foxgloves, and clusters of hosta, astilbe, alchemilla mollis (and alpine variety), primula, comfrey, iris, carex buchannii and geranium; two clumps of hellebore were inserted on the top of the bank, towards the east end to check growing conditions.
Initial planting started at the west end, and this had the benefit of introducing plants to areas which attracted some rain and the best of the sunlight. However, the bank and top area at the east end remained substantially dry after significant rain, and included the steeper slopes (in excess of the angle of inclination of soil). Trial plantings here included bluebell and lily-of-the-valley.
Carole Baxter’s recommendations
On a visit to make a radio programme for BBC Scotland, Carole Baxter commented on the need for uncovering the bases of trees and providing shade- and dry-tolerant ground cover; she later provided a list of plants (see below) and followed up with a tray of Waldsteinia Ternata which have been planted into the South Bank:
- Ajuga reptans (surplus planted late)
- Geranium macrorrhizum
- Lamium maculatum Beacon Silver
- Persicaria affinis
- Waldsteinia ternata (donated by Carole)
- Viola odorata (surplus planted)
- Pachysandra terminalis
- Vinca minor (purchased and planted late).
To complete the planting at low density (based on the assumption that current plants would spread to generally cover the bank), a lot of 50 Vinca Minor (9 varieties) was purchased, and planted in clusters (mid-July), mainly towards the east end of the bank. Ajuga Reptans were added in late July, and Sisyrinchiums in early August.
Additional plants for further infill will be sourced through plotters for early 2017. Proposed plants include lupin and primula.
In years to come
What we have done
We have placed priority on using our own plotters’ resources to populate the South Bank. This has meant using plants which are available, rather than a design selection. Some of the plants used are annuals, though the foxgloves should self-seed and may need replanting each year.
As a result, we have not yet achieved a low maintenance bank, and expect to make gradual progress towards this over the next years.
What we have learnt
- parts of the South Bank are very dry, particularly towards the eastern end. Here plants may need to be watered, and a longer term programme of mulching with organic matter may be beneficial
- perennial weeds thrive here as elsewhere on Garthdee Field. Particular emphasis will need to be made to control creeping buttercup on both the slope and top surfaces of the bank
- An active population of snails has taken up residence on the bank. Next year, we should carry out snail watch early in the year, to minimise hosta leaf damage
- access to the top surface is awkward and liable to cause soil loosening. Access to the top surface and top of the bank should be gained from either end of the bank
- current planting is generally free of scent; selected plants will be sought to enhance this aspect of planting on the bank
- woodland flowers may be of educational benefit for primary school visits. Bluebell and Lily-of-the-valley have been planted, and wood anemone and wild garlic could be sourced for planting (subject to confirming tolerable locations) in 2017.
Progress towards low maintenance South Bank
We aim to plant the top of the bank this autumn, with the following:
- fern at the base of the wall (generally shade tolerant and capable of existing in dry conditions)
- daffodil (1000 provided by ACC) along the middle of the flat section of bank
- primula on the front fringe.
An annual review will be necessary for the next few years, to understand:
- which perennials survive/thrive in their current locations
- if self-seeding from annuals (e.g. foxgloves) is successful, and any planting adjustment required
- which shade-loving plants can be added to the current planting (see list above)
- whether plants/shrubs should be sought to minimise longer-term maintenance.
Spring 2017 on the GFAA South Bank
It is now a year since we started planting on the “South Bank” area, and the mild winter has brought the benefit of survival for many of the early plantings. A number of the periwinkles are showing their blue flowers at present, as well as “pom-pom” primulas.
Late last year, we received several sacks of Daffodil “Ice Follies” from ACC, and these 2000 were planted in trenches on flat areas on top of the South Bank. They are now splendidly in flower – our thanks to our Volunteers and Stuart and Norman, who successfully laid these.
The bank is not yet “low maintenance”, and we will have a number of general tasks this year: (i) to track the success of intial plantings and the durability of the plants currently in the bank; (ii) to keep the bank free of weeds in order to enable the current plants to fully establish themselves. We have made good progress in taking out much of the creeping buttercup, though some still remains; and this year has produced an excellent harvest of sycamore seedlings which need to be culled. At the same time, we can indulge in a little light stone removal.