The pieces I have been given are from a still living Black Mulberry tree behind Lancaster Castle and which has provenance back to the James 1st planting.
"Italy had a thriving silk industry from the 13th century and France from the 15th century, using both black and (predominantly) white mulberry leaves to feed their silkworms. In letters of 1607 and 1608 King James I of England asked the nobility to plant 10 000 mulberry trees to support an English silk industry to rival that of the continent.
Silk production didn't take off in England, though, perhaps because black mulberries were planted and not white, which produces finer silk. Perhaps the cool, damp climate wasn't right"