This quest is one that starts in Denalan's planter after you've completed https://vanillawowdb.com/?quest=931 The Shimmering Frond, by activating one of the Shimmering Fronds that appears.

The quest requires fast action.

After handing in Shimmering Frond and Denalan goes to plant, hover the mouse over the planter and you should be able to pick up this quest. If not, it despawns in a bit and you will be unable to grab it. You also won't be able to go back to the shimmering frond tree to grab the prereq item again. Lastly, should any other player hand in a quest requiring the planter, that's another possibility for the despawn.

To make matters worse, this quest is an 'Accept and Complete' in one step. Because of this, the quest completion may not be noted by an addon like QuestHistory or EveryQuest. You should get 5 Sprouted Fronds in your bags, and that's your cue that it's done.

I had a long conversation with a GM about this, after being unsure my character received it. This was with game version 3.2.2.