Survey of giant hogweed, Japanese knotweed and Himalayan balsam on 5 major Lothian rivers, 2003/04
Over the five Lothian rivers surveyed:
Fallopia japonica (Japanese Knotweed) was by far the most extensive of the three species, often forming semi-continuous stands along riverbanks which were frequently, on the North and South Esks in particular, within important habitats such as native riparian woodland. The location of populations are hard to predict with frequent isolated stands being found where garden refuse has been dumped or disturbance to the bank has occurred for example. In general the plant occurs much more extensively in and around built-up areas and is much rarer in the more rural locations of the river systems upper reaches.
Heracleum mantegazzianum (Giant Hogweed) was the least widespread species which occurred only on the lower Esk in any profusion. Elsewhere it occurred as isolated small stands with at least one record on each catchment. Incidental sightings of this species were also made from the A1 where there are more extensive populations locally.
Impatiens glandulifera (Himalayan Balsam) shows a quite distinct pattern of distribution with well-defined upstream and downstream limits between which it occurs at near constant or very high frequency. On the rivers where it occurs the downstream limit is always the sea or a little inland where there is tidal influence as on the River Tyne. On some rivers there are small populations upstream of the main length of affected river.
The survey was carried out to assess the distribution and abundance of three key invasive non-native plant species through five main Lothian rivers to determine the severity of invasion. Other non-native plants were also recorded.
Highland Ecology, ecological consultants with experience of vegetation survey and alien plant survey, were commissioned to carry out the work. Many records were for transects; these have been reduced to 100 m point locations for the purposes of mapping. Approx. 39 records from the River Almond catchment were excluded due to errors in processing their grid-references, so the Almond is under-represented in the data.
Initial field survey was undertaken in September/October 2003 with walked surveys carried out over rivers and their main tributaries. In mid-October, shortly after the first frost and subsequent leaf/flower loss by key species, field work was halted in order to eliminate error in locating species which were harder to see. The survey was resumed and completed in June 2004. Where access was restricted either topographically or due to private gardens, these sections were noted or viewed using binoculars. Some lengths of river were not seen for various reasons, most commonly steep or dense woodland and private housing and grounds. Where this happened grid references of the limits of these were recorded. Some sections were, for similar reasons, only seen intermittently and again the reason recorded. A hand-held GPS unit was used to increase accuracy in obtaining location grid references for stands. However it was not always possible to take a reading due to trees blocking a clear view of the sky.
Proctor, K. & Rafferty, T.F. (2004). Survey of Giant Hogweed, Japanese Knotweed and Himalayan Balsam on five major Lothian rivers. Scottish Natural Heritage Commissioned Report No. 223
Looking up... the number of records that can be accessed through the NBN Atlas. This resource was last checked for updated data on 27 Jul 2020. The most recent data was published on 27 Jul 2020.Click to view records for the Survey of giant hogweed, Japanese knotweed and Himalayan balsam on 5 major Lothian rivers, 2003/04 resource.