I've just changed L11 to get rid of an "as", "as" advised 
Revised 19/03/12
When you and I were summer, and the sky
was greyer than the green that grew between
my linden and your oaken strength, serene,
eternal as the shadows passing by,
you whispered me a question; my reply
was lost upon the winds of might-have-been,
for change must come to every tranquil scene
and gifts from gods are not what they imply.
Forever is a dream lost to the dawn
and temples fall to dust beneath the years,
while roses split the stones and oceans dry;
yet boughs will bend and brave the tearing thorn
to claim the scars as treasured souvenirs,
and laugh until the summer, you and I.
Revised 19/03/12
When you and I were summer, and the sky
was greyer than the green that grew between
my linden and your oaken strength, serene,
eternal as the shadows passing by,
you whispered me a question; my reply
was lost upon the winds of might-have-been,
for change must come to every tranquil scene
and gifts from gods are not what they imply.
Forever is a dream lost to the dawn
and temples fall to dust beneath the years,
while roses split the stones and oceans dry;
yet boughs will bend and brave the tearing thorn
to claim the scars as treasured souvenirs,
and laugh until the summer, you and I.
Quote:Original Version
When you and I were summer, and the sky
was greyer than the green that grew between
my linden and your oaken strength, serene,
eternal as the shadows passing by,
you whispered me a question; my reply
was lost upon the winds of might-have-been,
for change must come to every tranquil scene
and gifts from gods are not what they imply.
Forever is a dream lost to the dawn
and temples fall to dust beneath the years,
as roses split the stones and oceans dry;
yet boughs will bend and brave the tearing thorn
to claim the scars as treasured souvenirs,
and laugh until the summer, you and I.
It could be worse