At this workshop with Alison Elvin we discussed weeds – why they are growing, how to identify them and what they look like in the paddock.
“Weeds are messengers – they can tell you a lot about your land and what is happening with the soil” Alison Elvin 2017
So why are weeds a problem and how can we manage them? Weeds are usually performing a function within the landscape or filling a niche where they can easily out compete other plants. They often grow on bare, acidic, compacted soils with little top soil. The most important thing that you can do to stop weeds getting a foothold is to maintain ground cover and protect top soil.
General weed management guidelines
- Accurate identification of weeds and your paddock plants is essential. Learn about what you have.
- Maintain ground cover by managing stocking rates and using mulch to protect small bare patches of soil.
- Most weeds set huge numbers of seeds that can survive in the soil for long periods. For example Serrated Tussock can set up to 140,000 seeds per plant per year. Stop weeds seeding in the current year by rotational grazing, mowing or other means. Cool burns at the right time of the year (with a permit) can help reduce seed.
- Killing weeds can be helpful for reducing spread – use mechanical removal methods where possible. If you use herbicides, only spray on calm, sunny days at times when plants are actively photosynthesising. This will improve the uptake of chemical. Use a funnel over the nozzle to prevent spray drift.
- Manage soil fertility – by improving soil fertility and taking soil samples you can address any mineral deficiencies in the soil. Cape Weed and other yellow flowering weeds indicate the soil is deficient in Calcium.
- Biosecurity – seed moves on vehicles, in and on livestock, in feed (e.g. hay) and by wind. Use quarantine paddocks for newly arrived stock, buy feed from reputable sources and feed out in restricted areas.
- When removing or controlling weeds – replace the weed with plants/seeds of the vegetation that you want to grow there. Sow seeds, plant shrubs/seedlings and spread mulch. On elevated ground, remove weeds and use mounds and swales made from vegetation or hay bales to trap seeds. Work in small patches to reduce erosion risk.
- Some weeds like thistles can be beneficial – they have very deep tap roots and exude secretions that feed fungi in the soil. Consider chipping the weeds and leaving the roots intact as this will help the fungi spread and improve soil fertility.
- Only use herbicides according to the label instructions and use personal protection equipment. Help reduce development of herbicide resistance by using integrated control methods. When selecting a contractor, ensure that they have Chemcert Training.
Serrated Tussock has an interesting history in Australia. It was introduced in pack saddles before WW1 and only became a problem after the Rabbit Drought. Serrated Tussock is a problem because it is highly unpalatable to stock, it has a high silica content and the microbes in the rumen won’t break it down. It will kill stock that graze it when there is nothing else to eat. Over grazing pastures will compound the problem because the weeds that are toxic to the stock will proliferate since they are the least desirable to graze.
Here are some tips to identifying Serrated Tussock and controlling it:
- Poa spp., Corkscrew Grass and other native tussock grasses flower in early spring, Serrated Tussock flowers in November and December.
- Serrated Tussock is usually a lime green colour when actively growing, native tussock grasses are more bluish grey. The seed heads of Serrated Tussock will blow around in late summer, native tussock will hold onto the seed heads (see photo). Serrated Tussock generally only flowers once a year. Native grasses can flower twice a year if conditions allow. Alison Elvins suggested that the best time to identify serrated tussock is in winter. Physical barriers and dense windbreaks on the boundary can reduce spread of serrated tussock because 70% of the seed heads move around 70-90 cm above the ground.
- If you need help with identification and management of weeds your Council Weeds Officers can assist you.
NSW WeedWise – NSW DPI website with descriptions and photos of common weeds along with information about control and management options.
Weed Spotter – ACT and Southern Tablelands website for reporting and mapping weeds and weed control actions – citizen science in action.
Weed Management Guide – Serrated Tussock – information sheet about Serrated Tussock issues, identification, spread and management options by CRC Weed Management.
Serrated Tussock Resistance to Fluproponate – information from the Serrated Tussock Working Party for NSW and ACT about the developing resistance to herbicides and how you can help reduce this problem.
This workshop was made possible with funding from the Australian Government and support from South East Local Land Services and Queanbeyan Palerang Regional Council. Thank you to our hosts for contributing to a successful day and our network sponsors, the Palerang Local Action Network for Sustainability.