[Gimp-user] How can I "Autumnize" this image of leaf that still has some green color to it?

[thegimpestgimp 9a neverbox com]

Hello,

We'd like to "Autumnize" the picture of a leaf that still has some green/life to it.  Leaf is located http://i.imgur.com/X9po8.jpg

We want to make the leaf take on the color of a bit more autumn: the green parts turning red. How can we do this without making the picture seem to "photoshopped" or too reddish?

 I've tried playing with the various options in the Color dropdown (Colour Balance, Hue Saturation, Colourize, Brightness-Contrast, Threshold, Levels, Curves), but I can't seem to do it.

Thank you.