The Queen's Heart is the Witch Queen's personal favourite flower which is located in her royal garden. It appaered in the 1st Movie where the Ojamajos had to capture it before it could spread it's seed in the Human World after Pop made a selfish wish upon it.
The Queen's Heart is a flower with 5 white heart-shaped petals and a small white stigma in the center, along with a little green stem, leaves and roots.
Every time a selfish wish is make upon the Queen's Heart, it's petals with change color; starting with pink, to red, to purple, and finally to black.
The Queen's Heart is capable of granting any wish regardless of whether it's good or bad. It only takes one selfish wish for the plant to gain a mind of it's own and flee off in search of more selfish wishes.