Mulberries were originally introduced to the greener parts of La Palma to feed silkworms for silk production. The fruit is a delicious side-effect. Sadly, you rarely see it on sale, because it’s fragile and doesn’t keep.
It’s also a strong, natural dye (and is used as such). If you pick your own, expect stained fingers and watch your clothes. In fact, if you’re staying near a mulberry tree in fruit, don’t leave washing out any longer than necessary, because they still dye even after it’s been through the inside of a bird.