Quick Mask
Select flower petals and the stem
1 Select > Color Range, adjust Fuzziness all the way to the right, and click on blue sky
2 Select > Inverse
3 Switch to Edit in Quick Mask Mode and use Brush Tool to select flower and the stem
4 Switch to Edit in Standard Mode and examine precision of your selection
Note:  The moment you switch to quick mask mode your brush tool has only black or white color to choose from.  Painting with white or black, means adding to or subtracting from selection.
5 When satisfied Feather (Select > Feather...) your selection by 2 pixels and copy it to the new document