From the Green Party website:
The Green Party of the United States formally recognizes two candidates for the 2016 Green presidential nomination, in accordance with party rules: Jill Stein and William Kreml. Both candidates have fulfilled all the requirements for official recognition, qualifying their campaigns for access to party resources.
The nominee will be chosen at the 2016 Green Party Presidential Nomination Convention in Houston, Texas, August 4-7, 2016 ( http://www.gp.org/pnc-2016 ). The nomination will take place on Saturday, August 6.