grass roots community organisation that aims to improve natural condition of the derwent catchment

Why Are Willows Bad

WHY ARE WILLOWS BAD??

Willows:

  • Choke watercourses, change flow, destabilise banks and consume large amounts of water
  • Are fast growing and can quickly outcompete native vegetation
  • Dominate entire stretches of riverbank, reducing habitat for native fish and animals
  • Create dense shade in Spring/Summer and heavy leaf fall in Autumn/Winter which impacts native vegetation growth and reduces water quality
  • Restrict access to rivers and streams for activities like fishing and kayaking
  • Are highly invasive: a fragment of willow branch can re-sprout by simply washing up on the river bank
  • Are one of Australia’s worst river and wetland weeds!

Removing willows...

Make a plan!

  • Seek advice and make a long-term plan
  • Work with your neighbours
  • Start in the upper catchment and work downstream
  • Remove dense willows in stages and revegetate riverbanks before moving on
  • The flow of the river will change once the willows are removed, and this can place greater pressure on restricted points downstream. In these cases, it may be better to start working on the lower end and progressing upstream
  • Work on the inside bends first, establish native vegetation

Control methods
Best practice control depends on the situation and circumstance, so seek advice. Things you need to con-sider when selecting a willow control method:

  • Only use herbicides registered for aquatic use near waterways e.g. Glyphosate products registered for aquatic use, without added surfactants.
  • Consider how you will dispose of living willow trunks, branches and twigs that you remove. Willows spread by stems, twigs and even wood chips growing new roots, so any living material must be dis-posed of away from waterways. If burning willow debris, locate burn piles away from river to avoid damaging and destabilising riverbanks.

Willow fragment lying on the ground

New roots sprouting

Which method is best for your situation and resources?

  • Stem injection: Large mature and iso-lated trees can be treated with glypho-sate registered for aquatic use, with-out added surfactants by making cuts or drill holes 30mm deep around the trunk at 100mm spacing, angled downwards. Immediately inject herbi-cide at the recommended rate. Leave the tree undisturbed for at least 12 months to die. Stem injection avoids chemical run off and the need to dispose of living willow stems and branches. Effective all year round, best results from summer to early autumn.
  • Cut and paste: For smaller trees which can be safely removed, cut the trunk off below the first branches and immediately apply herbicide to the cut stump and to the cut surface of the removed trunk. The trunk and branches need to be disposed of away from the riverbank. Effective all year round.
  • Hand pull: Pull out all seedlings and rooted branches while still small. Dispose of willow material away from the riverbank. Effective all year round.
  • Foliar spray: willows under 2m in height can treated by spraying leaves with glyphosate (registered for aquatic use, do not add surfactants) at the recommended rate. Care must be taken to avoid herbicides entering the waterway – direct spray away from river, only spray in calm weather and avoid spray when expecting rain within 4 hours. Only effective when plants are in leaf.
  • Mechanical removal: There is legalisation that applies to using heavy machinery near waterways and you may require a permit to remove willows using this method, so make sure you understand your legal obligations and contact your local Council before commencing. Using heavy machinery can help to remove large volumes of willow and debris and help with the safe disposal of this mate-rial. Make sure you leave willow stumps in place (to stabilise banks) and treat with herbicide using the cut and paste method. This method will require follow up foliar spray of regrowth from twigs and stems, as it can be difficult to remove all smaller material from dense infestations. Using heavy machinery along waterways can damage riverbanks and spread willows further, so make sure you get advice (and permission) prior to undertaking works. Effective all year round, avoid working in wet weather.

Restoring riverbanks

Planting native vegetation:

  • Will reduce willow and other weed species gaining ground
  • Ensures the stability of banks
  • Shades the waterway (which helps prevent future weed invasion)
  • Provides habitat for local fauna including animals and insects that inhabit the river

Other advice:

  • Seek assistance with what species to plant where from your local native plant nursery
  • If you have large areas of bare ground, sow pasture grass to supress weeds and then plant out with native trees and shrubs
  • It is vital to protect riverbanks from stock access while the area revegetates and control access once established