Ketu (Dragon's Tail) Puja is dedicated to planet Ketu. Grah Shanti Ketu Pooja (Worship of Dragon's Tail) is recommended for those, having malefic Ketu or wrongly placed Ketu as per the horoscope. Following things are associated with Ketu (dragon's tail):

Direction :	North-West
Flower :	Red Lilly
Gemstone :	Lasniya (Cat's Eye)
Metal :	Iron
Color :	Red
Grain :	Khollu
Food :	Rice mixed with Khollu
Dhyan Mantra :	Aum Palasa Puspa Samkasam Tarakagraha Mustakam, Raudram Raudratmakam Ghoram Tam Ketum Phanamam Yaham
Ketu Gayatri Mantra:	Aum Chitravarnaya Vidhmahe, Sarparoopaya Dheemahi, Tanno Ketu Prachodayat

In Vedic astrology, the South Node of the moon is called Ketu. Ketu is known as a shadow planet, because of the Node's association with the phenomena of eclipses. Lord Ketu is supposed to have the head of a snake and the body of an asura (demon). The temperament or nature of Ketu is fiery. Ketu is the planet of spirituality.

Ketu Puja / Worshipping Dragon's Tail
If Dragon's Tail is malefic in one horoscope chart then Ketu Puja is recommended to remove the malefic effects. People afflicted by malefic Ketu are stricken with fears of robbery, bad habits, putra dosham, loss of property, and loss of face. Reciting the following mantra after sunset, facing north - west direction, will really help to reduce the bad influence of Ketu.

Aum Hrim Krum Krura Rupine Ketave Aim Suh Svaha
Ketu brings prosperity to the devotee's family, removes the effect of snakebite and illness arising out of poisonous matter entering one's body. Dragon's Tail grants good health, wealth and all round prosperity.

Ketu - The Dragon's Tail & Its Position
Ketu has no sign ruler ships, although it is acknowledged to favor Mercury and Jupiter's signs according to some authorities, while others claim that Ketu favors the sign of Scorpio. Ketu stays for 18 months or 1.6 year in each grah.

Ketu - Its Significance
Ketu is an indicator of intelligence, liberation, wisdom, non-attachment, spirituality, fantasy, penetrating insight, carrier of arms and weapons, invisibility and physic abilities. Knowledge, business, leprosy, poisonous bites are different aspects of this planet. Ketu represents the spiritual process of evolution. Ketu is considered as a worldly malefic and spiritually benefice, as it causes sorrow and loss, which ultimately turns the individual to god.