Bring 10 Unidentified Plant Parts to Lauranna Thar'well at the Cenarion Refuge in Zangarmarsh. The entirety of this quest happens in Zangarmarsh.
"The lakes of Zangarmarsh are slowly being drained of their water. We don't quite know why, but we do know that many plants species are in danger of becoming extinct.As the expedition's cataloguer, it is my job to track and identify these plants so we can better understand what's happening to them.If you'd like to help, bring me unidentified plant parts. They can be picked right from the ground if you're an herbalist, and the indigenous creatures of the swamp may also carry plant parts on them".
Upon completion of this quest you will gain 1 400 experience and 250 reputation with Cenarion Expedition.
Here you can buy Plants of Zangarmarsh Quest Boost for EU or US Servers.
You'll get guide for completing Plants of Zangarmarsh Quest Boost