The Robin Hood stories are folk tales, meaning they evolved over time, and there's no historical record of a real Robin Hood. This means the specifics about his bow are largely up to the imagination of the storyteller.
However, we can make some educated guesses based on what we know about traditional English bows and the time period they're usually set in.
* Yew: Yew wood was the most popular choice for English longbows throughout history. It's strong, resilient, and flexible, making it ideal for bows. It's likely Robin Hood's bow would have been made from yew if he were a real person.
* Ash: Another possible choice, ash wood is also strong and flexible. While not quite as popular as yew, it was a common choice for bows, especially for people who couldn't get their hands on yew.
* Other woods: Other woods were sometimes used for bows, but they were generally less desirable. These might include elm, oak, or even fruitwood like apple or hawthorn.
Ultimately, the wood Robin Hood's bow was made of is up to the story you're reading or the adaptation you're watching.
It's important to remember that the stories of Robin Hood are fiction, not historical fact. While they are rich in detail, the specifics of his bow and other equipment are best left to the imagination.