Invasive Species

In 2010, a project to control Invasive Non-Native Species (INNS) within the Nith catchment was launched. The project has focused on the control of invasive species of plants such as Japanese knotweed, Giant hogweed and Himalayan balsam, all of which were introduced into the Nith catchment as ornamental garden plants. Unfortunately, due to their invasive nature these plants have spread into the wild, often resulting in many of our native species being unable to grow, thus reducing the biodiversity of our river banks.

In the Nith area, as elsewhere, the most effective method to control Japanese knotweed and Giant hogweed is by injecting Roundup (Glyphosate) into their stems, with encouraging results.

JAPANESE KNOTWEED



The treatment of Japanese knotweed started upstream of New Cumnock and systematically moved south, down the catchment, to Dumfries. This work will continue down through Dumfries and along the coast of the estuary. Treatment has also begun on the River Cairn.

Identification:

  • Green cane-like stems with red specks that can reach up to 2 - 3m tall.
  • Heart shaped green leaves up to 120mm long.
  • Creamy white flowers from August to October
  • Roots consist of rhizomes that can reach up to 3m deep!

Control Options:

Applying with a commercial glyphosate-based chemical such as Roundup ProBiactive is highly effective
  • Spraying - This should take place 4 times per year for a total of 4 years. The initial spraying should commence in May when the plant is 3 foot tall, and the final spraying should be in September just before the plant dies back for the winter. The two other sprayings should be within these dates during the summer.
  • Stem Injection - This should be carried out once a year for a total of two years. This should take place in August time when the plant is at its strongest to support the treatment. A follow up visit should take place to treat any stems missed.

Do's and Don'ts!:

  • Never throw away or fly tip plant material or soil - under the Wildlife and Countryside Act 1981, it is an offence to plant or otherwise encourage the growth of Japanese Knotweed.
  • Never strim, flail, mow or chip Japanese Knotweed - pieces of stem as small as a fingernail can grow into new stems.
  • Scottish Environmental Protection Agency (SEPA) should be contacted before any chemical control takes place near water.
  • Removal of plant material off site must be carried out by a licensed carrier

HIMALAYAN BALSAM



Although Himalayan balsam is an annual plant it is considered to be one of the hardest invasive species to control, due to its explosive method of distributing its seeds for metres around. The Nith Catchment Fishery Trust, following research elsewhere, will be experimenting to see if by using dilute concentrations of Roundup to destroy the Himalyan balsam, native flora will be able to thrive.

Identifications

  • Stems are sappy and hollow in pinky-red colour. They can grow to 3m, being the tallest annual plant in Britain.
  • Spear-shaped leaves with serrated edges. Dark green with a dark red midrib up to 150mm long.
  • Flowers are slipper-shaped on long stalks. They are purplish-pink and flower from June to August.
  • Seeds are white, brown and black. They are produced from July to October with 4 - 16 per pod that explode, throwing seeds up to 20 foot

Control Options

Spraying with a commercial glyphosate-based chemical such as Roundup ProBiactive is effective. This should be done when the leaves are fully out, but before flowering - typically in June

Cutting stems with a strimmer or pulling up hand before it flowers and sets seeds is successful.  This grazing technique is highly effective.

Himalayan Balsam can be disposed of by leaving to dry out onsite or by burning.

Do's and Don'ts!

  • Never throw away or fly tip plant material or soil - under the Wildlife and Countryside Act 1981, it is an offence to plant or otherwise encourage the growth of Himalayan Balsam.
  • Scottish Environmental Protection Agency (SEPA) should be contacted before any chemical control takes place near water.
  • Do not touch the plant when loaded seed pods are showing - they will explode showering seeds. Be careful not to transport seeds to a new site. Seeds can be hidden in clothing or on your dog for example.



GIANT HOGWEED



During 2011, all of the flowering Giant hogweed plants along the River Nith and Scaur were injected with Roundup, 52km of river bank. Giant hogweed flowers mature into seed heads with thousands of seeds each, which, once dispersed, can stay dormant in the soil for many years. This means that it is necessary to go back year after year and treat the newly emerging plants until the seed bank is exhausted.

Identification

  • Stems are hollow, green with dark or purple blotches and will grow up to 5m tall!
  • Leaves are dark green in a rosette with a jagged appearance and spiky at the ends. The lower leaves can be up to 1.5m long!.
  • Flowers are white with several hundred in large umbrella-like flower heads up to 50cm across, appearing from June - July.
  • Each flower will produce up to 50,000 seeds that are easily dispersed by water and can remain viable for up to 15 years

Control Options

Spraying with a commercial glyphosate-based chemical, such as Roundup ProBiactive is effective on Giant Hogweed. The plant needs to be sprayed once all the leaves are fully out, but before flowering. This is typically in June. Any re-growth can be sprayed later in the season. The plant should be controlled in 2 - 3 years, but will need future checking for any newly germinating seeds.

Cutting the stems before the plant flowers and sets seed is also an effective control option. This grazing-like method will stop the plant from producing seeds. This should be done for 2 - 3 years before achieving full eradication. Due to the health and safety issues with the 'skin burning' sap of Giant Hogweed, cutting should only be carried out by a qualified person.

Do's and Don'ts!

  • Never throw away or fly tip plant material or soil - under the Wildlife and Countryside Act 1981, it is an offence to plant or otherwise encourage the growth of Giant Hogweed.
  • Scottish Environmental Protection Agency (SEPA) should be contacted before any chemical control takes place near water.
  • Giant Hogweed should not be touched without protective clothing as contact with the sap can produce painful skin conditions

WHAT CAN YOU DO?

The Nith Catchment Fishery Trust are keen to hear from anyone that has reports of Japanese Knotweed, Himalayan Balsam or Giant Hogweed locations near watercourses within the Nith catchment area.

Dumfries and Galloway Council are equally keen to receive any roadside location reports by calling the main switch board on 030 3333 3000.

The Trust is now running a 'River Guardian' volunteer scheme to encourage interested helpers to take part in this important conservation project within the Nith catchment. A limited number of training opportunities are available in order to develop a strong team of volunteers to assist with ongoing monitoring and control.

If you wish to find out more information, or want advice on controlling these alien plant species, please contact Debbie Parke at:

The Nith Catchment Fishery Trust
37 George Street
Dumfries
DG1 1EB
Tel. 01387 740043
Email trust@river-nith.com
www.river-nith.com