Ponds, Pools and Lochans

5.8 Pond colonisation: is it necessary to plant up ponds?

It is sometimes thought that pond colonisation is a slow process and that adding plants and animals is necessary to speed up the process. Studies of pond colonisation have, in fact, shown that colonisation is usually a very rapid process, particularly where other wetland habitats (streams, ditches, lakes, ponds, bogs, fens) are reasonably close by (e.g. within 1 km).

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Figure 38. It is sometimes thought that pond colonisation is a slow process which needs speeding-up. In fact, pond colonisation is rapid and many species quickly find new waterbodies such as this four-spotted chaser dragonfly, especially where other freshwater habitats are nearby (i.e. within 1 km). Laurie Campbell

Not planting-up ponds can be particularly beneficial for wildlife. In its early years a new pond provides a distinctive environment when species that require inorganic sediments (such as stoneworts, darter dragonflies) can flourish, before being replaced by more competitive species or those that require organic sediments. Planting-up ponds is not inevitably harmful in itself - indeed if material is collected locally its effect is probably not much different to the natural processes that move plants and animals around (large grazing animals, wind, floods etc.). It just means that, unfortunately, some of the valuable early pond stages may be shortened.

What is harmful however, is the planting of non-native, invasive species. Initial surveys of Sustainable Urban Drainage System ponds in Scotland in autumn 1999 by Pond Action indicate that planting schemes are spreading Crassula helmsii and introducing ornamental versions of water lilies, irises, variegated reed sweet-grass and reed canary grass into ponds, as well as non-native plants such as Canadian pondweed (Elodea nuttallii and E. canadensis) and curly water-thyme (Lagarosiphon major).

Some of these plants have been added deliberately. Others, particularly Crassula, have come in accidentally with other plants.

The problem with these introductions are numerous:

  • many non-native species are spreading into the countryside and out-competing native plants. The DETR lowland Pond Survey in 1996 showed, for example, that 1 in every 6 occurrences of a submerged aquatic plant in British lowland ponds was a non-native.
  • even native species which are not of local provenance will have their natural genetic difference diluted
  • most new ponds will colonise up naturally with entirely appropriate new pond species - planting-up not only introduces troublesome plants, but takes out opportunities for distinctive native species to use the space
  • in some cases where invasive plants are threatening remaining colonies of nationally protected species it is essential that they are removed. The price tag for clearing ponds has sometimes been upwards of 50,000! - an unnecessary waste of scarce conservation resources.
Rules for planting-up ponds
  1. If only small quantities of plants for stocking are required, it is better to collect plants from the wild than use garden-centre stock. It is a requirement of the law that to do this you have permission from the land-owner (this applies to all plants, including common species) and that you do not collect any species which are uncommon or specially protected. SNH or SWT will provide information on specially protected species.
  2. For large planting schemes consider:
  • collecting water plants which are being dredged from streams, ditches or rivers.
  • collecting seeds and growing the plants on from a known local source. For large pond creation schemes landscape architects should be able to source local stocks of native plant material. Community groups could set up their own nursery of local origin plants. For more information contact Plantlife, FWAG or SWT.
  1. Dont buy plants from garden centres.
  2. If planting-up of bought stock is essential:
  • use suppliers who only deal in native species (so that soil is not contaminated with seeds of nonnative species) and who can supply ecologically appropriate plants for the area (see Appendix 2) including beneficial plants such as floating sweet-grasses (Glyceria fluitans, G. notata, G. declinata)
  • source plants that are of local provenance
  • get advice on the appropriate plants to introduce - e.g. do not add river or floodplain plants to upland ponds and vice versa.

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Figure 39. Rules for planting up ponds: dont buy plants from garden centres; instead collect plants locally (making sure not to contravene the Wildlife & Countryside Act, 1981) Lorne Gill/SNH
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