Yavanna's firstborn had been the Ents, crafted to protect what her husband's children and Men sought to destroy without regard.
Shaped by her desires, her wishes, the Ents stood to be stalwart sentinels standing strong, indistinguishable from other trees until the forests were threatened and the great guardians were called to action— sometimes by the dozens.
Then, whilst the Ents were away, darkness came and raised the woods that the Entwives and the Entlings inhabited— leaving naught but a cursed land behind and dooming the Ents to a silent extinction.
Yavanna became beside herself with grief, mourning her firstborn. The children she'd so lovingly crafted to protect the world and all things green, without them darkness would swallow everything whole and the folly of Dwarrow and Men would wipe her woods and prairies and meadows from existence.
Her husband's children held no love for her or her things, taking evermore. Stripping lands barren in their quest for geologic pride, in their quest for perfection of crafts. They did not care for the damage they wrought so long as they got their precious minerals and ores. As long as gold lined their pockets.
The Men-folk were scattered, but much the same as Mahal's Dwarrow. While some respected her, others saw her gifts as trivial; means to line their pockets.
Eru, seeing her plight, gave her blessing in the form of a Song. Not a complete one, but the start— the soul, really. It would be up to Yavanna to shape it.
Thus, came her secondborn.
Shorter than their Elf and Maiar cousins, shorter than even her husband's children, Yavanna made them closer to the earth than any other race. They would appreciate her smaller things and bigger things much more. She gave them large feet to feel the earth with, to feel the connection between them and her, and ears to hear dangers their shorter statures prevented them from seeing, so that they could hear the tiny things asking for assistance.
Yavanna wished them to be light-footed, so they could slip through the underbrush without disturbing it's inhabitants. Wished for them to be compassionate and love all. Wished them to give twice what they took.
Thus, Hobbits were born. Little things that lived in the ground, for they were of the earth, and loved all it's bounties. Some of the first became her Druids.
The Druids had no dogma, finding themselves and their spirituality in the creations of their Mother. They recorded, taught, healed, traveled, with their feet in the earth and their hands in peace.
Unlike the Maiar and the Skin-changers, her Druids did not pull their magic from the soul. They traded for it, giving in proportion to what they asked, offering thanks and requests in physical form.
When the darkness came once again, it was her Druids that stood first. Her Druids that laid down their lives in defense of Yavanna's children and her lands. When finally, her secondborn faced a similar fate, the remaining Druids —few in number now— lead their kinsmen into the Wandering Days.
Even more died during those days, and the druids became all but forgotten.