Answer:

sills

Answer	Crossword Clue
SILLS	Spots for window boxes
SILLS	Perches for houseplants
SILLS	Places to put potted plants

SILLS	Places for small herb gardens
SILLS	Places to cool it?
SILLS	Window ledges
SILLS	Places to cool pies
SILLS	Framework components
SILLS	Sash supporters
SILLS	Places for dust to collect
SILLS	Grammy and Emmy-winning soprano

SILLS	See 21-Across
SILLS	Places to set geraniums
SILLS	Red-haired soprano
SILLS	Potted plant sites
SILLS	Met star Beverly
SILLS	Window bases
SILLS	Places for plants
SILLS	Noted coloratura