I want to know why this photo was rejected.

I have the same rose in my backyard. It really isn't an unusual rose. It's very easy to get the bush on the internet. I would move on from this picture. 

Hello,

A further point to add, be careful of your composition!

Have a read from Adobe’s Help guides about composition:

Composition

And exposure:

Exposure

These were likely refused for improper focus and uneven lighting. 

Stock contains over 16 million roses. This is what you’re competing with.

https://stock.adobe.com/search?k=roses

https://stock.adobe.com/search?k=roses+multicolored

Read the 4-part section on Photo Requirements in your Stock Contributor User Guide below:

https://helpx.adobe.com/stock/contributor/submit-your-content/submit-photos/photo-submission-overview.html

DOF is too shallow in several of these, rendering parts of the flower out of focus.

Acceptance on other stock sites is not a guarantee that assets will be accepted by Adobe. Higher quality standards for one, but a different customer base as well. Best of luck going forward!

It’s a beautiful and unusual rose Veronica. Im wondering why there’s so much difference with the exposure on the photos, the dark photos are just too dark. Was the rejection for quality issues? Keep in mind Adobe will only take a limit on the same subject.

Also, I have learned for stock it is best to have more depth of field, and when you’re close like these photos adding 2-3 stops will help in with approvals.

So if they come from your garden, keep playing with them and enjoy them like Jodi says.

cheers!

Editing that significantly alters the color tone is not recommended.

https://helpx.adobe.com/stock/contributor/submit-your-content/submit-photos/photo-editing-best-practices.html

It is a pretty flower, but you are competing with millions. I don’t think the flower has much stock value, so I would enjoy the flower and not worry about the picture.

Other stock agencies have their own quality standards and have no relevance here.
Here are the reasons that I see:
1. Cropping. Flowers that are not zoomed in should be placed using the Rule of Thirds. Zoomed in images should have equal space on all sides.
2. Focus. The images need to be sharp and the depth of field should be extended.
3. Exposure. Th flower is slightly underexposed and the background should either be lighter or dark enough to exclude disturbing shapes. Also, the histogram shows no blacks and no whites.
Here a corrected example: