Start this quest by talking to Doctor Camden, who can be found on the Docking Bay/Common Area of the Nexus, near hydroponics. He’ll task you with finding plant samples on various planets throughout the Heleus Cluster. Given Havarl’s hyperactive flora, it should be no surprise that there are two such plants on this planet.

East of the Pelaav Research Station you’ll find a Forward Station, east, southeast of which you’ll find a search area for this plant. Climb uphill and search the foot of a tree near a Remnant wall to find a mushroom which can be scanned, then collected.
East of the Pelaav Research Station you’ll find a Forward Station, north of which are some Remnant structures (marked on your map as “To the Remnant Abyss”). Explore northeast of some ramps and work your way around some rocks to find a leafy plant with fibrous stalks. Scan and collect it to tick another plant sample off the list.