Well-drained soil is a must for nearly all flowers, the exception being bog plants that grow around and in ponds. A raised bed is an ideal solution for an area that collects excess runoff or rain. If the bed is already established or you don't want to go through the expense and effort of a raised bed, install a French drain with a PVC pipe with holes drilled in the sides.
Dig a trench that goes from the higher end of the flower bed to the lower. Continue the trench to an area of the yard that is down from the flower bed. The slope of the trench must continue to increase, so gravity drains the water to the selected area. The trench should be 5 inches wide and 6 inches deeper than the French drain pipe. It may have to keep getting deeper to maintain the downward slant.
Lay the pipe in the drain. The pipe has a narrower end and a wider end. Insert the narrower end into the connecting pipe's wider end. The pipe also has two sets of holes running down the length of the pipe spaced from 6 inches to a foot apart. The holes should be at the sides of the pipe, not facing up toward the top and bottom.
Cover the pipe with the drain sleeve cloth. Tuck the ends around the underside of the pipe to hold the cloth in place. The cloth keeps dirt, mud and debris from falling through the holes into the pipe. Water drains through the ground and into the pipe through the holes. The force of gravity pulls the water through the pipe, draining the flower bed.
Test the pipe by using a sprinkler to soak the flower bed. The water should start flowing through the pipe. If it doesn't, see where the water is pooling in the trench. You may have to make the slope a little steeper by digging the trench deeper.
Cover the pipe with soil. If you've removed sod from the lawn to dig the trench, replace the sod.