Shrubs have been forced into flowering in Aalsmeer since the 19th century, including lilacs. These are cared for on islands in the Westeinderplassen, after which they were brought into the greenhouse by barge after two years in October. There the temperature is raised considerably, so that the lilacs bloom scented with Christmas. Then the bushes go outside again. Shrubs can age tens of years.
Practitioners are the members of the Aalsmeer horticultural community, also known at Historical garden Aalsmeer http://www.historischetuinaalsmeer.nl/
In the past the lilacs raised a lot of money for the Christmas decorations of Estates and churches, but also for export. There are now a few growers left in Aalsmeer including Klaas Joren (see www.seringen.nl)
