Significance of using yam plant for pooja:
Yam is the only such plant, even when pulled out completely from the earth, will grow back. Yes, yam is dug out from soil and used as vegetable in many dishes. We need not plant it again. If watered again, yam plant would grow in the soil, where we dug out. For this reason, yam is considered as the symbol of fertility, and so is worshipped as goddess.
Procedure of the pooja:
On the auspicious day of Polala Amavasya women wake up early and clean the house then prepare prasadam. This pooja will performed by married women so Poleramma will safe guard their children from the diseases and death. Mostly diseases like Chicken-pox and Small pox. Because of the Rainy season flu like diseases spread easily for children so, women will perform the pooja to protect their children from diseases.They offers pooja to poleramma as per Sri sookta and chanting Shakthi or devi Mantra, Astrotram, 108 names of gouri devi etc “Raksha Thoram” or “Rakstha Daaram”(Sacred Thread – seven lines of white thread dipped in wet turmeric and a turmeric root(pasupu kommu) is tied to it) is also Worshipped during the Pooja. Women tie Raksha Daaram in their necks for gals and for boys(only below 12years) around their waist to seek her blessings.
More about the pooja:
Polala Amavasya is mostly a local festival in Andhra Pradesh, Telangana and it is also observed in Karnataka, Tamilnadu and Orissa. Polala Amavasya is also known as Pithori Amavasya. Women worship yam plant or yam as Poleramma at puja place and offer shodashopachar puja to the Goddess. Goddess Poleramma vratam/puja is quite similar to the Goddess Sheetal Saptami puja observed in North India.
She is the local diety, who guards the village borders(polimeralu), preventing the evil winds of illness from entering into the village. She guards children from infectious diseases.
You can read the vrata katha/kada Here