At 4736 17th Street you’ll find a large cork oak, native to Spain and Portugal – the scientific name is Quercus suber. The bark of this tree provides the cork used in wine bottles - if you push your finger into the crevices of the bark, you’ll feel the spongy quality that is characteristic of the tree. This is the largest cork oak in San Francisco, and there is a younger, smaller one planted next door at 4746 17th.