In an auction held in Holland in February 1637, 99 lots of tulip bulbs fetched a staggering 90,000 guilders, more than six million pounds in today's money. This was known as Tulipomania. It was a form of futures trading, as people purchased tulip bulbs at increasingly inflated prices with the hope that they would flower into the unusual range of colours.The variety of colour is produced by a small parasitic aphid, which weakens the plant.
This fascinating period is well documented by Anna Pavord in her book "The Tulip" . There is a fictional account in "Tulip Fever" by Deborah Moggach. Both are worth reading.