With the exception of the Secondary Quests that branch off from the main quests, there is only one called 'Herbalist's Tasks . It can only be started if you did the same quest in Act I. In case you missed the items or haven't done the other quests yet, the ingredients Solivitus wants can be found around the area.
Harlot's Blush Flower - Can be found on the west side of The Wounded Coast.
Dalish Tattoo Ink - Can be found in a **chest** in Sundermount.
The Varterral Heart - Can be found on the Varterral during the Mirror Image Companion Quest.
All the items are found during other quests so the exact locations will not be detailed here.