BillyWu, gorgeous plants!
Because you gotta make some adjustments depending on where are you taking pictures.
This can be done before on your DSLR or afterwards in photo editing programs (Lightroom/Photoshop/...)
It can be a bit of hit and miss if you do it before, because you don't really see true quality on those tiny screens on the photo camera.
And it can be a pain in the ass if you do it after. Many photographers are taking pictures in RAW format and do a final editing on the PC. This ensures that no data is lost and gives you a lot of room for improvements and final touch-ups.
I can recommend Adobe Lightroom because it's easy to use and great tool for organising your pictures.