You would have to dig pretty deep to be effective, but adding sand or small gravel and organic matter such as compost or soil conditioner will help. (I'm assuming you have clay) If the area is in a low spot with no effective way to run-off then the best draining soil in the world won't help. If you can create a path for the water to run that would help. You don't necessarily have to build a raised bed if you can sort of hump your gardens up so the water runs out of them and doesn't sit. But the water is going to go somewhere so you need to be aware of that too. Good luck! -Ais.
Ais, thanks for the word! You're right, I do have heavy clay, plus underground springs periodically moving that complicate things. I'm in the process of mixing more compost and conditioner, though around 1/3 acre of garden makes the job feel endless. We'll see. I've always thought that conditioner and compost would simply hold more water - never thought about them keeping the soil looser, therefore providing better drainage! Duh! Thanks again, Jan
Instead of fighting the soil, plant what it loves- there are dozens of beautiful choices from trees to groundcovers that can turn an unsightly "wet spot" into a unique spot. I know- had the same problem with an old unused septic tank area and some of the worst clay you'd ever encounter. I kept mulching it over with organic matter. Over several years I've planted everything from creeping jenny to cannas to maiden grass to camassia quamash ( some interest for every season).
It's now quite lovely and I never have to try pushing a mower through a bog again!