This is the locs where I found mine.
8S, 39W
9.7S, 36.0W
10.5S, 35.9W
9.7S, 36.9W
10.4S 36.2W
10.6S, 38.4W
8.6S, 36.2W
Best plan is to do the quests with Harrow Weed, Hill-borne Orchnei and Hill-born Woad together, as the all seem to grow around trees that the good and bad Earthkin are near.