There are a lot of problems with this photo, most noticeably is that it is not in focus.

This section of the photo seems to be your main focal point and when looking at it magnified to 100% you can see that nothing is actually in focus. Your depth of field (f1.8) is much too shallow and your shutter speed (1/17s) is too slow unless you are using a tripod.
A few other things to consider is the angle of the photo - looking at the top the horizon is not level (it should rotated about 6 degrees clockwise). The flash also creates harsh lighting with a few blown out hotspots (water on sidewalk) and some unwanted shadows (foreground).
Aesthetically, the broken flower in the middle of your frame is not very appealing, unless that is actually what you were trying to focus on. Even still, the question you would want to ask yourself is what is the commercial appeal of this photo? Who would buy it? What purpose could they use it? Photos of flowers are very plentiful in stock photography. The millions of flower photos that are already there are technically sound. If you do get flower photos accepted, the chances of anyone purchasing those photos are pretty slim and they certainly won't be big money makers. That being said, taking photos of flowers is a great way to improve your photographic skills.
I would suggest joining a local photography club or taking some online classes (there are many free tutorials online.) Practice a lot, get your technique down, be very critical of your own photos - look at them magnified to at least 100% if not higher and put yourself in the buyer's position as to whether or not you would buy your photos.
Best of luck, I hope this helps.
-Rob