Refuse collectors could carry out spot checks on some household rubbish to stop people flouting a new system of brown bin bags for garden waste.
Powys recycles the most waste in Wales
Powys Council, which wants to ease the burden on landfill sites, will charge 90p for the brown bags.
Regular black rubbish bags could be scrutinised to ensure they do not contain grass or hedge clippings.
The council said not every black bag would be searched, but would be if it appeared some contained garden waste.
The local authority, which already offers home composting bins at cost price, said it faced financial penalties if it continued at its current rate to dispose of waste in landfill sites.
To help resolve the problem, the council is also planning to open 30 more recycling centres.
The council's board has already voted in favour of the new brown bags. They could be in use by April.
Friends of the Earth welcomed the move to charge gardeners for the bags.
Spokesman Julian Rosser said garden waste produced methane, a greenhouse gas which was one of the causes of climate change.
Glyn Davies AM, chair of the Welsh assembly's environment, planning and countryside committee, said: "Irrespective of the negative reaction from the public on this matter, people have no choice but to recycle more."
In December, the Welsh Assembly Government revealed that Powys recycled 33% of all of its waste, putting it top of a recycling league table in Wales for the second year running.