I remember walking through the gardens looking at flowers and seeing behind the flower beds a group of palm leaves (or similar plant) growing out of one of those big 18" diameter clay pots. With the powerful sun lighting them from behind they appeared very colorful, and certainly bright enough to attract my attention. So, I am thinking that backlit flowers would be a good theme or project on sunny days. I need to remember that for the next time I feel like photographing flowers and it is a sunny day.
For these images I put the Panasonic GX80/85 with Olympus 60mm macro in my backpack, as the prime lens did not have enough reach, and pulled out my E-M1 with Olympus 12-100mm F4. Even zoomed in at 100mm (200mm equivalent) this image is cropped a bit. One reason I always bring a zoom with me is that botanic gardens have rules about walking on the paths only. This means if the desired flower or subject is off the beaten path, you have no option but to go for a longish zoom or telephoto lens.