Milton's Mulberry Tree can be found growing in the Fellows' Garden at Christ's College, Cambridge. It was planted in 1608, the year of John Milton's birth and was named in his honour, as a former student of the college. It is said that he sat under it when he composed Lycidas.
James I, King of England, was a keen gardener. He decided that it would be a good idea to encourage silk production in England and decreed that 10,000 mulberry trees be established throughout the land as food for the silkworm. He paid his adviser, William Stallinge, £935 to make a mulberry garden, and seeds were distributed to anyone prepared to grow a mulberry tree on their estate or in their garden. Stallinge got it dreadfully wrong, however, and ordered Black Mulberry trees which are far less suitable for silkworms than the preferred White Mulberry.
Three hundred Black Mulberry trees were bought by Christ's College for the sum of 18 shillings, but the Milton Mulberry is the only one remaining. The tree that now stands in the garden is probably an offset of the original, having grown up from the roots as the old trunk died off. The fruit is carefully harvested by hand every year and made into mulberry jam/jelly - it is said that the fruit of the mulberry improves with the age of the tree, so the fruit from this tree must be truly outstanding!
http://www.botanical.com/botanical/mgmh/m/mulcom62.html
http://journeytoforever.org/edu_silk_mulberry.html
www.christs.cam.ac.uk/info/tour/