I  found the following quote the other day in a 1924 edition of "The Book of
 
Wild Flowers".  It is remarkable that this plant has been spreading for >70
years and is just now eliciting a response like we are seeing.  I think
beekeepers have little to worry about this plant being damaged by pests that
 
feed on it  in Europe.  The threat to native species by the insects  may end
 
up being a problem however.  Since they have been released in
Canada it is probably only a matter of time until they spread here anyway.
 Colonization of new species is a natural phenomenon and  we will have to
live with the consequences of it regardless if it is a plant or insect or if
 
it gets here on its own or is given a lift by man.  We can make a best guess
what the
outcome will be, but only time will tell.
 
From  "The Book of Wild Flowers", The National Geographic Society,
Washington, DC, 1924
 
An immigrant from Europe, loving wet meadows, marshy places, and banks of
streams, and flowering from June to August, the purple loosestrife has
secured a foothold in North America and thrives from eastern Canada to
Delaware and from the Atlantic seaboard to the Middle States.  So beautiful
is it that many are ready to forgive Europe for all the weeds it has sent
us, when they see an inland marsh in August aglow with this beautiful flower
 
born to the royal purple.  The purple loosestrife is different from any
other heretofore mentioned, because it has what are known as trimorphic
flowers.  Being unable to set seed without the aid of insects, the purple
loosestrife has devised a most ingenious sort of arrangement to make sure
that it shall not pass away until its flowers have been fertilized.
This plant produces six different kinds of yellow and green pollen on its
two sets of three stamens; these six different kinds of pollen are deposited
 
on the stigmas, which are of three different lengths.  Darwin showed that
only pollen brought from the shortest stamen to the shortest pistil and from
 
the other stamens to the pistils of corresponding length could effectively
fertilize the flower.  He found that the reproductive organs, when of
different length, behaved toward one another like different species of the
same genus, both with regard to direct productiveness and in the character
of the offspring.  When he made his famous discovery concerning trimorphism
of the loosestrife, he wrote to Gray, the botanist: "I am almost stark,
staring mad over Lythrum;... for the love of heaven have a look at some of
your species, and if you can get me some seeds, do."
 
David Winkler