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Center for Aquatic and Invasive Plants Logo    Plant Management in Florida Waters

Center for Aquatic and Invasive Plants Logo    Plant Management in Florida Waters

Machinery that chops and cuts herbaceous and woody plant materials and organic sediments and allows them to sink to the bottom, or facilitates the harvest of floating debris.


(Refer to floating island and tussocks to understand origin and impacts.)

Water uses and functions

  • Applied when other control methods are not feasible or when expedited control is required
    • Control floating masses of peat, or muck that cannot be controlled with herbicides
    • Control floating islands or tussocks in emergency situations
  • Flood control
    • Shred jams in flood control structures
    • Unplug jams in outfall canals, streams, rivers, or other conveyances
  • Transportation / navigation
    • Shred plant masses or organic material jammed against bridges
    • Shred plant masses or organic material blocking established navigation channels
  • Control drifting floating islands or tussocks in urgent or preemptive situations
    • Prevent potential damage to public and private property i.e. docks, bridges, etc.
    • Recreation and safety – prevent blockages to trails and public boat ramps

Fish and wildlife

  • Avoid shredding during wildlife nesting or fish bedding periods if possible
  • Prevent plant masses from covering valuable fish and wildlife habitat
  • Non-selective – controls plants and animals that cannot escape its path

Control feasibility

  • Shredding generally proceeds faster and is less expensive that harvesting
  • Expenses are generally high
    • Acquisition cost of machinery
    • High maintenance
    • Operating costs – depends on plant type and suspended organic composition
      • herbaceous vs. woody plants vs. trees up to 10 inches in diameter
      • no suspended organic material to peat up to four feet thick
  • Minimize adverse impacts to extent possible when shredding floating islands or tussocks
    • More difficult in emergency than urgent or preventive situations
    • Turbidity
      • Shred from interior of floating island or tussock toward outside
      • Leave edge for containment barrier
      • Allow as much shredded material to sink or decompose prior to harvesting barrier
    • Sediment accumulation
      • Shred floating islands where they arise – return organic material to point of origin
      • Shred as finely as possible to enhance decomposition
    • Try to avoid:
      • repeated shredding in same area
      • shredding on residential shoreline or public beaches
      • in canals or established navigation channels
    • Harvest floating shredded material where feasible – refer to harvesting considerations
      • Most material sinks to bottom while some remains at surface
      • Gasses build up during decomposition and may resurface organic material
      • Allowing shredded material to remain at surface as long as possible
      • Exposure to air enhances decomposition and compacts organics
      • Reshred material or harvest when vegetation grows over exposed organics
    • Push or guide floating islands to lower use or value area if possible prior to shredding

Other considerations

  • Avoid shredding notches or irregular areas in fixed-in-place tussocks or floating islands
  • Wind or water currents will catch edge breaking new material loose

Examples of Feasible Control:

  • Emergency shredding of floating islands blocking structures or outfalls alleviated flooding in Marion Creek, and Lakes Hancock, Miccosukee, Apopka and Runnymeade
  • Emergency shredding of floating tussocks prevented damage to bridges over the Withlacoochee and St Johns Rivers
  • Shredding drifting islands in Orange Lake and Tsala Apopka prevented boaters from being stranded and prevented from returning to public boat ramps
  • Shredding and harvesting drifting floating islands in Lakes Pierce and Apopka prevented further damage to boat docks and boat ramps
  • Shredding reopened navigation channels overgrown by floating tussocks in tributary creeks of the St Johns River and Lake Lafayette
  • Shredders chopped up about 1,000 acres of floating islands and tussocks to facilitate dredging operations on Lake Panasoffkee