The Greengrocer is a woman who can be found between two buildings across from the Saloon in Socorro Town in Oregon. She is where you begin the They Taste Yummy herbalist missions. She looks like ordinary female civilians in Socorro Town.
She has only been available through the update since no one have not seen her in the Windows Phone version. If you're having trouble finding her, use the road sign to travel to Socorro Town. Turn slight left towards the well and you will find her behind those buildings.