noun
burning fallen leaves; autumn leaf burning
Seasonal activity in autumn; often associated with the smell of burning leaves and nostalgic scenes.
公園で落ち葉焚きをしている。
They are burning fallen leaves in the park.
落ち葉焚きの匂いが秋を感じさせる。
The smell of burning fallen leaves evokes autumn.
焚き火 is a general bonfire or open-air fire, while 落ち葉焚き specifically refers to burning fallen leaves.
Compound of 落ち葉 (fallen leaves) and 焚き (burning), from the verb 焚く (to burn).