The Weeping Willow of the Van der Werf Statue

The register entry for this willow has a field for its history. The field says: unknown. That is close to the whole record. The Dutch national register of monumental trees lists it as standing at the water, by the statue, in the Van der Werfpark, and puts its planting between 1900 and 1910, which makes it roughly 120 years old. It is municipal property and anyone can walk up to it. Beyond that one entry we have found nothing: no newspaper piece, no park survey, no local history page that names this tree at all. The park's two planes and its silver maples get written about. The willow does not. Even the species is a common name rather than a determination. The register calls it a Treurwilg, weeping willow, and gives no scientific name. In Dutch parks that usually means Salix babylonica, though the hybrid Salix x sepulcralis 'Chrysocoma' is the commoner modern planting, and nothing we found settles which of the two is standing here. What it does have is position. It stands at the water's edge beside Pieter van der Werff, the mayor who held Leiden through the Spanish siege of 1573 and 1574, in a park laid out in 1886 over ground a gunpowder explosion had left in ruins. If you know who planted it, or what it is, tell us.