Harvest Witch

Harvest-witches are primitive nature magic users. While not widespread, they have existed on the fringes of Gilnean society, and are mostly found among Gilneas' agrarian peoples. Gwen Armstead refers to Celestine of the Harvest as a "harvest-witch". Although Celestine herself refers to her order as "druids".

King Genn Greymane had heard that "druidism was practiced among some of Gilneas's agrarian folk, but he hadn't been exposed to it until recently".

Celestine claims that her order of Gilnean druids were "driven to the edge of extinction once before". Celestine also refers to her druidic order as "keepers of the old ways".

Practices of primitive druidism or "the old ways" were once alive and well within or around Gilnean society before the sealing of the Wall. In time though (before the Greymane Wall was erected) the followers of the Holy Light must have spread their teachings to Gilneas and succeeded in converting many of its people, causing druidism to slowly fade into the past and become mostly forgotten.

The extinction of the Gilnean druids was prevented, however, by a Gilnean famine that struck when their crops failed. Celestine claims it was their order who "called upon the earth's blessing and restored the harvest".

Harvest-witches have a limited control over nature, especially plant life, and the powers of harvest witches bear a coincidental resemblance to the low-level abilities of actual Kal'dorei (Night Elf) druids. Harvest witches who contracted the Worgen curse (which was druidic in origin) found that their powers were somewhat amplified, and after making first contact with the Night Elf cursed harvest witches were offered induction into the Cenarion Circle for both study and training.

While Harvest Witches are predominantly female, male Harvest-Witches are not impossible. They're often referred to as "Harvest Warlocks" or "Harvest Watchers." Although, the Lupoj'inini peoples in the Duchy of Kentillie do not abide with any grammatical gender noun-class system in this respect.

Background
In the early days of humanity and its civilization, many tribes of humans had primitive belief systems that incorporated simple nature magic. However, the rise of organized religion such as the Holy Light and the potent arcane magics introduced by the high elves quickly supplanted such traditions. Gilneas, due to its relative isolation, has retained a degree of their ancient culture in the contemporary era. The religious leaders of what was in Gilneas referred to as the "old ways" eventually became "harvest-witches"; those who used their nature powers to augment Gilneas' agricultural output during and following its period of ndustrialization.

The presence of harvest-witches like Celestine suggests that Gilneans already had a good start with druidism. She makes reference of druid practices being "the old ways" and recounts a time when their powers supplied food during a time of famine, pointing to druidic roots as a base, even before night elf contact. This is agreed with in "Lord of the Pack" short story when Genn Greymane stated "He had heard that druidism was practiced among some of Gilneas's agrarian folk, but he hadn't been exposed to it until recently". It seems many Worgen have at least tried to embrace the druidic heritage of their new race after their transformation. This can be seen as a coping mechanism, or the fact that the natural powers can help them keep control of their animalistic rage.

Gilnean druids may have been capable of shapeshifting even prior to contact with the night elves. It's when King Greymane sees a night elf shapeshift out of flight form that reminds him of Gilnean druids.

The Lupoj'inini
The Lupoj'inini are an almost extinct group of native Gilnean people living around the dense forests and tall mountains within the Duchy of Kentillie.

Origins

 * The harvest-witches seem to thematically be based on the real, historic druids of the ancient Celtic people, as opposed to the druids in the rest of the Warcraft franchise which, aside from the name, are actually rather different from the historic druids. This matches Gilneas being based on Victorian England, as the Celts lived in Britain long ago.
 * The fate of the old Druidic religion of the Harvest-witches being replaced by the Worship of the Holy Light, and having been driven to the fringes of Human society to near extinction, shares similarities with Druidisim in the real world and how it was eventually replaced and driven to near extinction by the growing power of Christianity.
 * Celestine of the Harvest also connectied Gilnean, druidism, and the traditions of Hallow's End.

Information was taken from:

http://wow.gamepedia.com/Harvest-witch & http://wow.gamepedia.com/Worgen