Office greenery is a term used to describe the plants and other foliage that are kept in an office environment. The most common type of office greenery is the FERN, which is a four-letter word that can be found in many crossword puzzles. Ferns are known for their lush green leaves and ability to thrive in low light environments, making them ideal for indoor spaces. They also help to purify the air and reduce stress levels, making them a popular choice for offices.