Wormwood

Artemisia absinthium or Wormwood

Chunks of information

It is used in companion planting to suppress weeds, because its roots secrete substances that inhibit the growth of surrounding plants. It is sometimes used in beer. Wormwood is the traditional colour and flavour agent for green songpyeon (a type of dduk/tteok, or steamed dumpling/'cookie' made of fine rice flour), eaten during the Korean thanksgiving festival of chuseok in the autumn. (Wikipedia)