• Introduction
• Evaluating the potential for natural recovery
  • Burn severity & plant survival
  • Noxious weed cover & survival
• Revegetating with competitive plants
  • When revegetation is necessary
  • Formulating a Seed Mix
  • Things to consider
• Establishing competitive plants
• Managing competitive plants
• Integrated Weed Management
• Preventing noxious weeds
• Eradicating small weed patches
• Managing large weed infestations
  • Mechanical control
  • Chemical control
    • Timing & placement
  • Cultural control
  • Biological control
• Monitoring & Evaluation
• Developing a burned-area IWM plan
• Summary
• Sources and Credits
• Additional Resources
• Interactive Exercises

Rangeland Weed Management - Managing LARGE weed infestations

Mechanical Control

Where equipment can be brought onto the site, mowing can be an effective method for managing some large-scale noxious weed infestations, especially when mowing is integrated with cultural or chemical treatments. The effectiveness of mowing is based on timing during the growing season and the biological characteristics of the target weed.

When to Mow Weeds

Properly timed mowing reduces weed competition and limits seed dispersal while encouraging desired plant growth and vigor.

Infestations with a moderate to high cover of desired vegetation should be mowed short when the weeds have reached the flowering stage and the grasses are dormant.

Depending on the type of dominant grass, some weeds will bolt and extend above the height of these grasses. If the desired vegetation has not dispersed its seeds or is not yet dormant, mowers can be set to cut just above the grass seed heads. This defoliates a percentage of the weeds, reducing their vigor and seed production while increasing the availability of resources to desired neighboring plants. Unrestricted grass growth also allows seed dispersal for next year’s stand and maintains the strong competitive vigor needed to minimize weed reinvasion.

Mowing can increase weed density through increased germination from seeds in the soil or by stimulating shoot production from root buds in rhizomatous weeds. Mowing annually at roughly monthly intervals during the flowering stage can effectively weaken an infestation over time by affecting underground reserves. Revegetating (if necessary) and combining mowing with an appropriate herbicide applied one month after the last mowing can enhance management.