Anyone with green fingers could well be pleased to know about the biannual Botanic Gardens swap and buy market. The times are usually 09:00 to 14:00 hrs. Knowledge of German and the ability to ask questions in German may be required as the plants aren't usually labelled, or easily identifiable. Another market will take place in September.
S-Bahn (S1 green line - www.hvv.com) Klein Flottbek - between Blankenese and Altona. Parking is easy nearby. Map: http://stadtplan.hamburg.de
Click 4 Botanic Gardens website and details: http://www.bghamburg.de/veranstaltungen/boersen.asp
I might try and get down there early.
