In a report to the Central Otago District Council on gorse and broom control earlier this month, Boffa Miskell senior principal Marcus Girvan said about 180 carmichaelia, or native broom, had been sprayed.
They had been "misidentified" as Scotch broom.
"Immediate steps were taken to ensure this does not occur again, including producing plant identification material for all our contractors and a change to our contracting procedures," the report said.
"We are currently working with the Haehaeata [Natural Heritage] Trust to develop a plan to replant these areas."
The report noted it would take two to three years to grow plants to a size viable for planting.
Boffa Miskell could not be reached for comment.
There are 24 species of carmichaelia, all but one native to New Zealand.
They are not considered to be closely related to introduced Scotch broom, which is classified as a noxious weed.
