|“||I wouldn’t have paid any attention except... well, it was Luke.||”|
–Juniper, in The Battle of the Labyrinth.
Juniper lives near Zeus' Fist (the pile of rocks at Camp Half-Blood), and stays within her tree most of the time, watching the Camp. She isn't a fan of dogs because, in her own words, she "knows about dogs and trees." Juniper and Grover start dating before The Battle of the Labyrinth.
Juniper is first seen while she was attending Grover's trial by the Council of Cloven Elders, being comforted by Clarisse and Annabeth. Later, she tells Percy that she saw Luke Castellan entering the rock where the Labyrinth's opening is in camp, near her tree. She also recalls seeing Quintus doing the same thing. Juniper warns Percy not to trust Quintus.
During the battle, her tree almost gets set on fire and Percy stops the fire that was damaging her tree, and she joins the battle after that. She also uses a "Whipping Stick" in battle.
In the Demigod Files, Grover seems to say that the tree nymphs were so beautiful that he had to remind himself that he was dating her, and so he asked them to edit that part out, or Juniper would kill him.
Juniper calls Percy to a meeting with Leneus and Nico, telling him that Grover has disappeared, and she is very worried and heartbroken. At this meeting, Nico is embarrassed and blushes when Juniper puts her hand on Nico's arm. Percy soon finds that Grover had been entranced into a deep sleep by Morpheus and wakes him. Grover is frantic about what Juniper must have gone through while he had been missing for two months and says she is going to kill him, and hurries back to camp. Juniper is very worried about Grover Underwood during the battle at Olympus, but luckily, he survives.
In celebration of Grover's birthday, Juniper frolicks with the nature spirits of Long Meadown in Prospect Park, Brooklyn while Grover and Percy Jackson sit on a nearby bench, watching. Their day is interrupted when Apollo arrives to assign a quest to Percy and Grover.
Apollo sees Juniper over by the forest.
Before the three-legged death race starts, Will said that he missed Grover and Nico told him to shut up because Juniper was beside them, and that she was missing him very much.
Juniper is a very sweet wood nymph, and is very loving towards Grover. She is usually worried for Grover and is jealous of his liking of other wood nymphs. When Grover was in an enchanted sleep, she wondered why he was gone so long and is worried that "he might be with another tree" and that "he once had a crush on a blueberry bush."
Juniper is small and petite, with wispy hair the color of amber, and a pretty elfish face. She wears a green chiton and sandals, and is said to be a very pretty girl. When Juniper blushes, her skin turns green with chlorophyll, instead of red, her eyes are green and when she cries, her tears are also green.
Although Juniper's life source is tied to her Juniper bush which usually limits her to the vicinity of Long Island (where the bush is located) Juniper is able to take short trips away from home as long as she keeps a handful of Juniper berries inside her pocket.
- Juniper was set to appear in film adaptation of The Lightning Thief, and was to be played by Mikayla Midgett. However, she wasn't present in the book.
- Juniper is a coniferous plant, family of cypress.
- In Polish translation her name is Kalina. This mistake is most likely caused by the fact that in Polish Juniper is a word of masculine genre, while Kalina (viburnum tree) is not only a plant's name, but also feminine given name. Aparently, translator Agnieszka Fulińska intended to make some names and idioms more familiar to Polish readers, that's why she mistranslated Juniper's and several other characters' names.