There are many ways to change backgrounds in your images, or add textures in Photoshop. But one of the easiest for small subjects like flowers is to make your own and use in the garden. I use 11×14 foamcore to mount these, one on each side, and then carry into the garden. You can cut your own foamcore or order. Amazon has offerings, here is just one available today for reference: https://www.amazon.com/Pack-11×14-White-Foam-Backings/dp/B0072ZH97S

My favorite backgrounds are mainly in one color family, like greens or yellows or browns.

1. In Photoshop click on Filters > Blur > Gaussian Blur.  You will need to take the slider almost completely to the right to get rid of all detail.
2. You can adjust levels and color balance or use hue/saturation. If you create a nice mottled look, you can use that repeatedly by coloring it differently.
3. Print out your image. You want to keep reflections at a minimum so I find matte is the best finish. Lustre sometimes works fine depending on the lighting.
4. Mount on the foamcore. One piece can have two backgrounds, one on each side as I mentioned.
5. You can have a plamp hold this in place or often you can hold it yourself if close enough or use a timer on your camera.
6. Below I have added a third option – select a highly feathered circle on your texture and brighten slightly so an individual flower is really showcased with the effect of a vignette built in!