The Magical Birthstones are dropped by every 10th spotted Zodiac wildlife of the same kind (so there are 12 Magical Birthstones). Each one will be able to nurture a certain baby wildlife that will first feed in your garden if you have the correct food left out. Check the Babies page to find out more.
Unlike other plants in Fairyland, this one has no seeds that are available in the Shoppe. The seed itself is planted by every 10th, 20th etc. of certain Wildlife spotted in your Garden. The growth stages (after it's grown 50%) are fully grown - nurturing baby wildlife (the baby is inside the bubble; and blinking when expected within 30 minutes) - ready for harvest (there is no bubble on top of the plant)
More info on the Babies here.
This is the message left by the Baby Wildlife when it's announcing its very soon arrival/birth: The Baby <certain Wildlife> has opened its eyes!
(This means the bubble will pop and it will be feeding for the first time in less than 30 minutes!)
When the Baby Wildlife is born, the Magical Birthstone has served its purpose so it loses its color, turning grey.
But don't worry, you can still use it as a simple pot for your plants :)