Overview

• Thousands of monarchs have blanketed the south-west WA town for roughly two months, coinciding with the Nannup Flower and Garden Festival.
• Horticulturists say larvae rely on narrow-leaf cotton bush and milkweed, which are thriving near pine plantations and along the Blackwood River.
• The plants are declared weeds that can overrun bushland and invade crops, prompting calls to curb their spread.
• Local organisers and experts back targeted removal in bushland and roadsides to limit seeding while retaining some habitat to keep butterflies in town.
• Tourism operators report a visitor boost and viral attention, though experts caution the spectacle depends on the weeds and may not recur if control succeeds.