For general garden views you'll need an aperture small enough to get the whole garden in focus. However, be mindful of selecting too slow a shutter speed because plants can be blown around by even a gentle breeze, and will be blurred. Be prepared to raise your ISO setting to ISO 400 to enable you to use the aperture and shutter speed combination that you need.
Winner, Plant Portraits: Mandy Disher
A simple, almost monochromatic composition of a Cosmos Sonata. ‘I wanted to try to capture its wonderful ethereal qualities,' says Mandy.
Canon EOS 450D, Tamron 90mm Di Macro lens
To single out individual plants (or parts of a plant) within a garden, you'll need a wider aperture to throw the background out of focus and make your specimen stand out. (Using a telephoto lens will help exaggerate a narrow depth of field.) Use your camera's Depth of Field Preview to check exactly how much of your subject is in focus, or take a test shoot and zoom in on your LCD screen.
Finalist, Plant Portraits: Carol Sharp
A 75-300mm tele-zoom used at a wide aperture heped create the ulta-shallow depth of field in this picture of a wild umbellifer, which Carol found growing in a rough bit of land in Umbria, Italy. Nikon D200, 70-300mm, f/5
Can't get a shutter speed fast enough to freeze the movement of your plants as they blow in the breeze? Try setting a really slow shutter speed to deliberately blur them. This can sometimes produce great results, especially if there are other elements in the scene that are sharp. You'll need a tripod, of course - motion blur looks very different from camera shake.
Runner-Up, Garden Views: Claire Takacs
Claire composed carefully to use the ornate Snake figure as the foreground focal point, with the native Black-eyed Susan wildflowers and their reflections in the water as a backdrop. Canon EOS-1Ds, 17-40mm