Answer:

bulb

Answer	Crossword Clue
BULB	It's used in a flash
BULB	Light source that needs occasional replacement
BULB	Light source

BULB	Something screwed into a lamp
BULB	Hardware store or nursery purchase
BULB	Daffodil-to-be
BULB	Sylvania product
BULB	Tulip or lily planting
BULB	Bottom of a lily
BULB	Thermometer's terminus
BULB	Flower starter

BULB	Gardener's purchase
BULB	Iris's base
BULB	Thermometer part
BULB	Tulip planting
BULB	It's often screwed up
BULB	Tulip's base
BULB	Future flower