Suffolk has few natural geological outcrops, so our ancient buildings and stonework provide a unique habitat for a range of wall plants that would otherwise be unlikely to occur in the county.
Churches and churchyards are particularly important for these plants. The antiquity of the buildings allows colonisation by slow growing lichens that can take over a hundred years to grow only a few centimetres.
The geology of the stonework is often varied. When coupled with different aspects and natural weathering, this offers a wide range of micro-habitats, each supporting a distinctive plant community. Cool north-facing roofs and walls are ideal for shade-loving ferns, mosses and lichens. In contrast, a sunnier aspect may be colonised by plants adapted to hot, dry conditions such as the diminutive rue-leaved saxifrage or the succulent houseleek that often grows on roof tiles.
Lichens, mosses, ferns and small, flowering plants cause little or no damage to stonework and are an important part of the character and natural heritage of our churches. However, some larger species, particularly woody plants such as ivy, bramble, elder and buddleia can have a detrimental effect. It is therefore important that such plants are managed to ensure they are not damaging either the buildings or the more delicate plant communities.
With the aim of ensuring that parishes can preserve their church buildings while maintaining the special plant communities that they support, the Diocese of St Edmundsbury and Ipswich and Suffolk Wildlife Trust have drawn up the following guidelines.
Ferns, mosses and lichens
It is recommended that these plants be retained wherever possible. If removal is necessary for restoration work, some plants should be left undisturbed to allow re-colonisation. If plants are localised or in low numbers, it should be possible to work around the plants. Small ferns can be left in place and mortar applied around them as necessary. Mosses can cause problems if allowed to build up on north-facing roofs as they hold water; this can cause premature deterioration due to frost damage, particularly on red clay tile roofs. The quantity of mosses can be reduced by carefully scraping some of them off.
Small flowering plants such as whitlow grass, rue-leaved saxifrage, biting stonecrop and houseleek should be retained wherever possible following the recommendations above for ferns, mosses and lichens. Larger flowering plants such as wall flower and pellitory of the wall present something of a dilemma, as they are very much part of the characteristic flora of stonework, but can become quite woody and penetrate the mortar. Probably the best approach is to remove any plants causing damage to the structure and paint the stumps with a glyphosate-based herbicide. Spraying is not recommended as it results in the destruction of surrounding lichens. It may be possible to retain some of these larger flowering plants at the base of the wall in the footings.
Tree saplings, bramble, buddleia and other woody plants
These plants can penetrate stonework and be very damaging. It is difficult to remove or extract these plants without causing worse damage. It is therefore recommended that plants are cut off as flush as possible to stonework and the cut surface be painted with a glyphosate-based herbicide. Spraying is not recommended as it is damaging to surrounding stonework flora. Once the root has died, it may be possible to carefully remove it, or, if this is likely to damage the masonry, the root can be left to rot away. The cover provided by woody plants can support breeding birds. Cutting back should not be undertaken during the bird-nesting season (mid Feb – end July). It is an offence under section 1 of the Wildlife and Countryside Act 1981 to intentionally take, damage or destroy the nest of any wild bird while it is in use or being built.
|Immature strands of ivy growing from the bottom of the wall can be pulled off, but if it is penetrating the stones, bricks or mortar it should be cut off at the base and the stump painted with a glyphosate-based herbicide. The ivy above the cut will die back and lose its grip. When completely dead, the ivy can be removed, taking care not to disturb historic masonry. If ivy is well established or has reached the arborescent stage it may support breeding birds. As above, cutting back should not be undertaken during bird nesting season (mid Feb – end July). It is an offence under section 1 of the Wildlife and Countryside Act 1981 to intentionally take, damage or destroy the nest of any wild bird while it is in use or being built.|
The use of soft lime mortar is recommended for repair and restoration as it is breathable, reasonably resistant to frost, and allows moisture transfer through the mortar rather than masonry units, which is good for the long-term conservation of ancient masonry. It also gives a more natural ‘weathered’ look to stonework and supports lichens and ferns.
Phased repair and restoration
Whenever feasible, it is recommended that repair of walls is phased rather than an entire wall all at once. Islands of lichen-rich mortar should be left to allow re-colonisation. Sound areas of mortar should be selected for the islands. Architects may be able to recommend renovation in stages at each quinquennial.
To avoid damage to stonework and valued plants, the use of herbicides needs to be carefully targeted. Spot treatment by painting with suitable herbicide is preferred as it is very accurate and there is no drift. Spraying the footings of churches to stop tree saplings and ivy establishing at the base of the wall is best avoided. If spraying is considered absolutely necessary it should be restricted to the crack at the base of the wall by protecting the footings and base of church wall with sheets of plywood during spraying.
If herbicides are used, it is important to adhere to the legislation requiring people to hold the necessary certification for herbicide use and to implement necessary health and safety measures.
Listed building legislation
The majority of churches and many ancient buildings and monuments are protected by listed building status and it is important to ensure that any work complies with this legislation. These guidelines have been drawn up in consultation with English Heritage, however further information on listed building legislation and advice on specific situations can be obtained by contacting: English Heritage - East of England Region on 01223 582700 or via their website.