When the nakshatra mandala (nakshatra zodiac) is mapped to the rasi mandala (rasi zodiac), while certain nakshtras are fully mapped within the boundaries of a rasi sign, there are some which crosses over to different rasi signs. For instance nakshatras such as Ashwini and Bharani are contained within the boundaries of Aries while Krittika's one pada (quarter) in Aries and another 3 padas are in Taurus.
Such nakshatras, part of which falls in two signs behaves like bridging nakshatras between the signs. Considering the 4 padas of the nakshatra are 4 petals (of lotus), for such nakshatras one or two padas fall in one sign and the remaining fall in the another sign. They are called the pushkara nakshatras as the fall the bridge between two signs for movement of energies.
For the nakshatras of Sun viz., Krittika, U.Phalguni and U.Ashadha, one petals fall in the preceding sign and 3 petals fall in the succeeding sign. Similaly for Jupiter's nakshatras viz., Punarvasu, Vishakha and P.Bhadra 3 petals fall in the preceding sign and 1 petal fall in the succeeding sign. They are called tripushkara nakshatras as 3 of their petals fall in one sign. For Mars's nakshatra however, viz., Mrigashira, Chitra and Dhanistha, the petals are equally divided into 2 signs and hence they are called Dvipushkara nakshatra.
It is noteworthy that no bridge exist between the signs on the two sides of Gandanta viz., Pisces-Aries, Cancer-Leo and Scorpio-Sagittarius.Hence there are no energy transfer between those signs, hence planets placed in the last nakshatra pada of watery sign and the first nakshatra pada of the fiery sign suffer destruction (starvation) due to lack of resources. It is known that the houses whose lords are placed in the mentioned padas suffer heavily.
The Dvipushkara nakshatras and the tripushkara nahshatras i.e., that nakshatras of Mars, Sun and Jupiter offer a delicate balance in the horoscope. The planets placed in those nakshatras have special significance both in Natal and the electional charts. Functional benefics placed in those nakshatras confer outstanding results while functional malefic confer terrible results.
The means by which the results are attained will be based on the nature of the planets: natural benefics will undertake benevolent means, natural malefics will undertake malevolent means. Thus when natural malefics become functional benefics, the native will gain from evil means or after some mishap signified by the malefic planets.
There are panchanga yogas based on this principle while causes an event to occur twice (dvipushkara) or thrice (tripushkara).