I have been taking nature photography for over 15 years. Plants, flowers, and macro photography can yield amazing detail and color of this kind of photography. I visit places that are known areas that yield a wide range of plants and flowers. Botanical gardens are a great place to visit, but always remember to respect the gardens to not damage the plant or flower to get a photograph.
The best time to photograph plants and flowers is on a cloudy day. Sunlight creates shadows that are hard to work with. By using reflectors or shades helps me control the sunlight. With macro photography I use the Canon 180 Lens so a diffused light on my flash helps or using off camera flash.
Plants and flowers are best photographed on a cloudy day. Mainly, the sunlight can make it more difficult because of the shadows. However, sometimes the light is needed to keep shutter speeds fast and keep the ISO setting in the camera low. Therefore, I sometimes use a flash with a diffuser to even out the like. Another advantage of not using a flash or having sunlight is the use of a polarizer filter. Using this kind of filter, the rich colors of the flower can come out more.
The equipment I usually use is a lens that works best to fill the flower in the field of view. However, this will vary based on the distance of the plant or flower. A telephoto works well when the flower is more distant, but keep in mind that the depth of field is very narrow. The other use for a telephoto lens comes in handy when I focus on one single flower in a field of flowers. By using the lens wide open, the focus is usually one subject such as a flower.
Macro photography, which is another type of nature photography, usually is mostly flowers. When using a macro lens, a flash can be very useful when hand holding the camera. However, I also always use a tripod and manual focus when doing macro photography with flowers.