Dragon Age 2 Quest Reference: Act 1 - Secondary Quests - Herbalist's Tasks
Requirements: Long Way Home
After you complete the Long Way Home, go find Solivitus in the Gallows. He'll offer you a quest to gather some items he needs. You'll find the items he needs during the course of your travels. It's really a two part quest, the first part is in Act 1, where you have to find the items below. The quest will stay in your current quests log even after you deliver these items since it continues in Act 2. Note: If you found the Map of Occupied Kirkwall in the Dalish camp, Teryn is nearby so you can deliver it.
Spider Silk Gland: You'll find this one during the Magistrate's Orders quest. It's available even if you haven't started the Herbalist's quest yet. In the Ruined Passage, the first spider you fight with a lot of health with have this on its body after you kill it. It has to be collected before the Magistrate's Orders quest is over, otherwise you won't be able to get it.
Dragon Fang: You'll find the fang on the Mature Dragon at the end of The Bone Pit quest before you leave the mines.
Ironbark: Go back to Sundermount and visit the Dalish Camp. Speak to Ilen to find the location. It's called the Ironwood Clearing in the Free Marches. You'll have to kill a bunch of Hurlocks and an Ogre, then follow your marker to find the Ironbark.
If you manage to get all the items back to Solivitus in Act 1, his shop will be upgraded for Act 2. Giving them in Act 1 will also unlock the Nice Crime You Have Around Here quest if you haven't already done so.