Originally Posted by kay

"plants that drink a lot" won't be enough to solve that. If there's somewhere it could drain to, then you could put in some drainage. Otherwise, you'll need to plant things that don't mind getting their feet wet now and again.

the fact you describe it as mud suggests it doesn't have a very high humus content.

A good way to distinguish between sandy and clay soils is to roll a bit of soil between your fingers. If you can roll it into a ball, or even a worm, without it falling apart, then it's a clay soil. Clay plus humus = loam, so it's not a bad thing to have.