The apples were planted from the fruit branches that Gaea gave to her as a wedding gift when Hera accepted Zeus. The Hesperides were given the task of tending to the grove, but occasionally plucked from it themselves. Not trusting them, Hera also placed in the garden a never-sleeping, hundred-headed dragon named Ladon as an additional safeguard.
The golden apples were called the "Apples of Immortality", and it was believed that whoever ate of them will become immortal.
Hercules' 12th labor was to retrieve the Golden Apples from The Garden of the Hesperides. First, he flattered the Hesperides, but they didn't give him the apples. Then he found Atlas and convinced him to give him the sky for a little so Atlas went to see his daughters and they gave him a golden apple. Then Atlas gave the apple to Hercules.
In The Titan's Curse, Percy described the Garden of the Hesperides as the most beautiful place he had ever seen.
The grass shimmered with silvery evening light, and the flowers were such brilliant colors they almost glowed in the dark. Stepping stones of polished black marble led round either side of a five-storey-tall apple tree, every bough glittering with golden apples of immortality.
Percy also stated that he could not describe the reason for the appeal of the apples, but as soon as he smelled their fragrance, he knew that a single bite from one of them would be the most delicious thing that he had ever tasted. In fact, if it were not for the dragon coiled around the tree, he wanted to step right up and pluck an apple.
In Percy Jackson's Greek Gods, Gaea's wedding gift to Hera was described as a "young apple tree bearing solid gold fruit".
Hercules is sent to steal one of the apples in the garden as one of his labours. After Hercules arrives at the Garden, he realises he could not best the dragon Ladon so he convinces Atlas to pick the apples for him while Hercules held up the sky. Atlas, after picking up the apples realised that he had a chance to escape but Hercules managed to trick Atlas into holding up the sky again while he made his escape. This made Atlas curse at Hercules a lot. Perseus also meets Atlas in his travels. There are many variations of this myth but the most commonly accepted one is that Perseus eventually left after realising he couldn't best Atlas.
It does not appear, but it is said by Luke that he was scarred while attempting to pick apples (a quest he was sent on by Hermes) from the tree by the dragon Ladon. He failed in his quest, but he managed to return with one of Ladon's claws. This defeat makes Luke question and resent the gods however.
Zoë Nightshade, a former Hesperide, attempts to get past Ladon, and get her and her companions to safety, but Ladon realizes after a few minutes that Zoë is no longer a Hesperide and attacks her. She and her fellow quest members manage to escape, but Zoë is poisoned by Ladon. This later comes into effect after Atlas strikes her with a sword accelerating the speed of the poison spreading across her veins and quickly dies. Artemis then turns her into a constellation.