The red willows grew on the back of a gigantic turtle which lived in the Black Mud Swamp. Most of the willows looked like normal trees and grew in a spiral shape around their leader so that the free spaces between them formed a path leading anyone who landed on the turtle's back to the leader tree.
The Leader Red Willow looked like a big withered willow tree with three yellow eyes and a mouth full of pointed teeth (possibly implying that it was a carnivorous plant) and was the only willow to be really red in color. It gave off a reddish gas which made all creatures around it sleep.
When the Winx went to the Black Mud Swamp after Flora moved there to prepare for her exams and find the Cheerful Gladiolus, they met the Water Nymphs who told them that there was an enormous monster in the Swamp which threatened them. The Nymphs explained to the Winx that they needed a plant called Xylith which they used to make their homes, and that it grew on an island at the center of the Swamp, but that the monster was a constant danger to them. So a nymph would sometimes volunteer to go to the island and pick Xylith leaves and shortly before the Winx went to the Swamp a nymph named Lusiz went to pick some Xylith but never came back.
The Winx decided to fight the monster, but it captured Musa in its mouth and the Winx had to go underwater to save her. After saving Musa the Winx landed on the island and went towards the Leader of the red Willows. They nearly all fell asleep there except Tecna who found out that the Leader tree was giving off a kind of sleeping gas and created a bubble which woke Bloom up. They made the other Winx girls wake up. The Winx then made the bubble become bigger and awoke Lusiz who had been in constant telepathic contact with the environment surrounding her and found the truth about the monster. She explained them that there was actually no monster but that in fact it was a giant sleeping and sleepwalking turtle which was asleep because of the Willow's gas and that when it moved in its sleep the Nymphs would take its head moving in and out of its shell for a monster.
The Leader Willow then tried attacking the Winx but it was finally defeated by Bloom and Flora and the turtle moved away after letting the Water Nymphs picking Xylith leaves from its back. But the Nymphs only had some leaves and Flora used a rapid-growth formula of hers to make more Xylith plants grow for the Nymphs, who gave her the Cheerful Gladiolus as a present.
The Leader Red Willow tree is different from the other Red Willows, which look like normal trees with green leaves and brownish trunks. It is larger than the other trees, looks as if it has withered, has few leaves and is completely red in color, and it gives off a sweet-smelling reddish gas which makes all nearby living creatures fall asleep. What is more unusual about it is that it has what looks like 3 eyes, a mouth, and holes on its trunk acting as nostrils and, even if it cannot change its place it can move on the same spot and use its branches as if they were arms. It is very aggressive.
- After Flora and Bloom defeat the Leader Red Willow, Queen Algae says tha the Giant Turtle was now free. This might mean that a new Leader Red Willow cannot grow once the current leader has died.
- The aggressiveness of the Leader Red Willow is similar to that of the Whomping Willow from the Harry Potter Series.
- In The Lord of the Rings, the Old Man Willow is an evil willow tree/Huorn who can direct all paths towards him and tried to trap the hobbits by making them fall asleep. Samwise Gamgee and Frodo Baggins tried to burn Old Man Willow but he threatened to kill the Pippin and Merry who trapped inside its roots. The hobbits were saved when Tom Bombadil arrived and 'sang' the tree to sleep.