window box

plural window boxes · alternative windowbox

1. A narrow box filled with earth, placed on a windowsill and used for growing plants.

   As the world's drug habit shows, governments are failing in their quest to monitor every London window-box and Andean hillside for banned plants.

   2013 August 10, “A new prescription”, in The Economist, volume 408, number 8848, archived from the original on 10 Aug 2020

   Synonyms: flower box, herb box, planter

2. One of the hollows in the sides of a window frame for the weights which counterbalance a lifting sash.