When does the grass turn green in Paris?
 

And the first flowers start to bloom?

late March.

Things start to change in mid-March to late March, but if you really want blooming flowers and lush greenery, you may not see it until late April. The weather is highly variable and these dates can move forward and backward a lot from year to year.

I have been in Paris in mid March in 2002 and 2004 and the grass was green both times. There were daffodils, a few tulips, forsythia, and flowering almonds all in bloom and a few of the trees had tiny buds (no real leaves though).

Here is the link (I hope) to a small album of shots I took the first week in April last year. I love flowers...

http://tinyurl.com/a4mjx

I don't know why this shows up twice when I post, but click on the second link.

Oops, the link appears twice in edit, only once when posted.