While it may appear to be nothing more than a small ice-blue gem, the Seed of Snow Flower is actually, as the name implies, the seed of a very rare flower, called Snow Flower. However, the flower can't grow just anywhere. The seed needs to be planted in a special place, where it is very cold, yet with plenty of light and a regular source of water. The flower will bloom within a few weeks of these conditions being meet.
In Harvest Moon, the seed can be obtained from the Hawker at the Flower Festival for 2000G. It would be planted on Mt. Summit on the first of Winter. Watering it everyday would eventually help it to bloom, upon which, a fairy would appear and grant the player a Power Berry.