Take side and back lit shots with the sun behind the plant instead of behind the photographer. To avoid sun flares on the film, hold an umbrella above the camera lens, or your hand, or stand in the shade of a tree. Use a tripod if you have one. If not, hold the camera steady as you press the shutter. Holding your breath helps keep the camera steadier.
Most fuzzy pictures are the result of camera movement rather than faulty focus.
Lighten dark shadows with a flash or some sort of reflector. Aluminum foil, crumpled and then smoothed out, reflects light softly into the shadows. After you have mastered the art of garden photography, you can enter your photos in the local county or state fair next summer.