poor draining soil

If one area is lower than the rest, an option is to dig that area deeper, maybe fill with stones. Other areas will drain into the deep one. Pond plants should grow in the drain area

The usual panacea for drainage problems is to incorporate lots of organic matter (manure or compost, etc), which loosens the soil. But it really depends on why your soil is poorly drained - is it the soil type, eg clay, or is it badly compacted or is the watertable particularly high in your area? If either of the two former, then the above should help, If the latter, then you are probably stuck with it and should maybe consider planting trees and shrubs that are tolerant of such conditions. Hope this helps.