Ponds, Pools and Lochans

7.5 Planting-up SUDS ponds

Should SUDS ponds be planted-up?

SUDS ponds will normally be planted up with tall emergents for two main reasons (i) to aid their functioning and (ii) to provide safety screening. In addition, planting may be appropriate in some urban areas to provide a visual interest and give a finished look to a scheme. However, for nature conservation purposes planting-up is not necessary and wherever possible (within the constraints given above) should be avoided.

New ponds usually show a very rapid rate of natural colonisation. Assessment of ponds in the pilot survey of Scottish SUDS schemes by Pond Action, for example, showed that within a year or two of their creation most SUDS ponds supported 15 - 20 species of native plant which had arrived purely by natural means. These species were always more appropriate to the pond habitat, landscape and water quality than plants which had been deliberately introduced as part of planting schemes.

In urban landscapes, where it may be necessary to install a reasonable level of landscaping around new waterbodies, any planting should focus on:

  • The careful use of native species of local provenance.
  • Inclusion of at least some plant species which are particularly wildlife friendly e.g. grasses such as Glyceria fluitans (floating sweet-grass) and Agrostis stolonifera (creeping bent) which provide a good habitat for newts and other invertebrate animals.

Click to enlarge image
Click to enlarge image
Figure 41. Where possible in SUDS schemes, create habitat complexes with pools that vary in their depth and permanence. Try to include small marginal pools which are fed by clean runoff water from the slopes of the SUDS basin.

In addition, be aware that planting schemes can also add to pollutant levels in SUDS ponds. Topsoil addition, fertiliser use and regular soil disturbance in the pond surrounds will all increase runoff of nitrates and phosphates into ponds, and increase nutrient caused pond problems such as blooms of algae and duckweed. To stop such problems:

  • Follow good practice guidance for slopes above waterbodies to minimise nutrient run-off e.g. (i) ensure slopes are rapidly vegetated to minimise soil erosion, (ii) create trenches near slope bases to hold eroded sediment above water level.
  • Minimise, and preferably avoid, the application of topsoil in areas next to water bodies. Almost all native wetland species, for example, develop well when planted directly into subsoil.
  • Create low maintenance landscapes around SUDS water features (e.g. grassland, perennial shrubs). Avoid gardened areas which require digging, weeding or application of fertilisers and pesticides since these will continually add to waterbody pollutants.
  • Try and locate terrestrial planting beds (e.g. ornamental shrubs) so as to minimise nutrient-rich runoff into waterbodies, i.e. plant so that run-off from bare soils is directed away from ponds or filtered through a grassland buffer.
Sources of wetland plants for SUDS schemes.

As noted above, ensure that wherever possible, plants introduced to SUDS schemes are native species of local provenance.

As a possible source of plants it is worth noting that large quantities of wetland plants are commonly removed from streams, ditches, drains and other wetlands in the course of legitimate countryside management activities. In some cases the re-use of this local plant material may be a possible source of appropriate plants. Organisations such as British Waterways, the Scottish Wildlife Trust and Scottish Conservation Projects may know of suitable sources.

The most practical alternative source of plant stock for SUDS ponds is provision of stock from plant nurseries which fulfill the general requirements given in Section 5.8, Rules for Planting up Ponds.

It was noted in the survey of Scottish SUDS schemes described in Section 7.1 that a very high proportion (about one third) of all SUDS ponds contained the highly invasive alien plant Crassula helmsii. In most or all of these cases the Crassula appeared to come from seed contamination in the soil of other planted stock.

Such findings are very worrying. There is increasing concern about the effects of highly invasive alien plants in the UK. Three species pose a particular threat: Crassula helmsii, Hydrocotyle ranunculoides and Myriophyllum aquaticum.

Because of the problems associated with alien plants, every effort should be made to take a strong line in Scotland in resisting their spread. To do this, it is important to ensure that plant stocks are bought from nurseries which grow only native species so that crosscontamination is unlikely.

Another experience from Scottish SUDS schemes is that there was often a considerable difference between the landscape architects original planting specification (e.g. for native wetland species of northern origin) and what was actually delivered by the nurseries (which was often a high proportion of non-native aliens). This clearly points to the need for detailed post-implementation appraisals of planting schemes as well as the potential for inclusion of corrective measures if species such as Crassula are found.

Species which can be planted

In practice, most common native marginal wetland plants are likely to establish well in SUDS schemes, unless pollution levels are excessive. There is, however, rarely likely to be any point in planting submerged plants: introductions are often unsuccessful, and submerged species are more likely to colonise by natural means if the pond is suitable for them. In the survey of Scottish SUDS ponds, for example, all ponds had naturally colonised with between one and four submerged plants; few, if any, of the native planted aquatics appeared to have survived.

Lists of desirable plants given in pond management guides often give the impression that a standard list of plants is desirable and appropriate in every pond. In reality, planting schemes should be (a) restricted to the plants which are already growing in the locality (e.g. within 10 km of the site) (b) appropriate to the physical and chemical conditions. Do not, for example, plant up a pond in a acid water area with the plants of base-rich soils.

The lists given in Appendix 2 show species which are widespread and common in Scotland and which may be suitable for planting. Do not treat this list as a recipe but get local information about what are the common water plants for a given county or district. This information is usually available in floras (contact the Scottish Wildlife Trust or SNH).

A typical semi-natural pond in Scotland could be expected to support 20-30 species of wetland plants (it could be as many as 50 species on a large site - say 1.5 ha).

Most planting lists make little mention of the plants of acid waters which are highly characteristic of many areas of Scotland. In appropriate locations, there is no reason why these plants should not be incorporated into planting schemes.

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