Sheaf of Wheat
Seasonal decoration at The Cloisters (The Medieval Branch of the Metropolitan Museum of Art), a sheaf of wheat placed on an alter. In the farming communities of eastern, central and northern Europe wheat was one of the most important crops grown. In the Ukraine, a sheaf of wheat is called didukh, it literally means grandfather spirit, symbolizing a family's ancestors as well as the staff of life. In some interpretations a sheaf of wheat represents the harvest which is the end of the world.
Greek/Roman mythology - Demeter, as she is known in Greek or Ceres to the Romans is the goddess of agriculture and very often represented with symbols of a bountiful harvest such as sheaves of wheat or corn.
She is also the mother of Persephone who must return to Hades each year. This story symbolized the annual cycle of death and rebirth in nature, as well as the immortality of the soul. Demter's worship involved fertility rites and rites for the dead, and her chief festival was the Cerealia. joy at her daughter's return, Demeter caused the earth to bring forth flowers, fruit, and grain in the spring. Her sorrow returned each fall when Persephone had to go to Hades. Winter was regarded as the yearly manifestation of Demeter's grief.
My interpretation is that if you have enough wheat in the dead of winter to be using it as decoration you have enough wheat stored to be able to eat until the next harvest - it's all about the circle of life.