Notes on Impatiens noli-tangere

Impatiens noli-tangere L. (Balsaminaceae) on a boulder on brook side (Finland, Lohja, 2000). – Photo: Harri Harmaja. – The plants of this stand may differ somewhat from the typical ones. The spur is generally more curved (often even 180º), the flowering time may be somewhat later on the average, and perhaps the seeds are not fully identical, either. – Harry Krogerus made an experiment to test the floating capacity of the seeds of the indigenous I. noli-tangere and the closely related introduced species I. capensis Meerb. (Memoranda Soc. F. Fl. Fennica 53: 99-100. 1977). He himself had brought seeds of the latter from Newfoundland and disseminated them in Lohja (South Finland) in 1949. The plant soon colonized numerous localities on the shores of lake Lohjanjärvi, obviously in the hydrochorous manner. Dr. Krogerus used the water of that lake in the floating experiment. It turned out that all the seeds of I. noli-tangere had sunken to the bottom of the test vessel in three days. On the contrary, 97 % of the seeds of I. capensis still floated after 21 days when the test was terminated. – In late summer of the year 2001, inspired by that experiment, I put 16 ripe and undamaged seeds of I. noli-tangere from the plants illustrated above into water from Helsinki city waterworks. The result I got was surprising: 100% of the seeds floated after 21 days, and still 88% after 30 days when I terminated the experiment! The reason for this result, quite opposite to that obtained by Krogerus, is unclear; the conditions under which the tests were conducted were of course not quite identical.