The weeping willow is a sallow tree, known for its love of water. Find a brook or ford and a willow will be there, lost in its reflection.
That familiarity with water makes willow a strong wood for fishing rods. There's the merest wisp of magic running through it, an affinity for water. The fish recognise that affinity and relax. They circle until they're caught, which is pretty handy for an angler.