I sowed marigolds and other flowers at the allotment to encourage useful insects and to deter the baddies. They've been remarkably successful. These photos were taken in the middle of October where the marigolds still growing really well and have needed no maintenance, except for a bit of deadheading every so often.
This site gives tips for other goodies in the garden or allotment: http://toadstoolponds.wordpress.com/2007/12/07/why-plant-marigolds-in-your-vegetable-garden/
