Difficult to see the photo as on my monitor it is upside down. You are sure up for a challenge though by the sounds of it.

Ok, I think I rotated the picture. I also added on drawing for one potential bed shape--long and relatively narrow. My current planting area is so wide, I am drawn to the idea of having a narrow area to help provide better delineation of the plants. Also, if it is not too wide, I will not be tempted to plant more and more plants in it. I am striving for a less crowded bed focusing on early spring display (peonies, sweet williams, allium, iris, hardy glads -- they have to be deer resistant at least somewhat). Then I hope to have a few plants to carry over interest for the rest of the year, but there I am not sure. Maybe some low mounding greenery.

Another possible design is a kidney bean shape toward the end of the yard as shown below. My existing planting area could be reined in a bit at that end but still flow out to include my cherry tree. The cherry still could be moved, but I'd rather avoid this.

Without seeing how this bed relates to the rest of your property and especially to your house it's difficult to advise. However, I think one of the problems may be that it is a rectangle. Seems it might look less like a 'blob' if the edges were gently curving.

Have you ever considered installing a dry stream bed which could channel the water toward the drain? It would in reality possibly become a wet stream during rainy weather. I've always wanted one as they can add so much interest to a garden. I'm not sure how having a retaining wall installed will solve the problem unless you have underground tiles to channel the extra water. Might be worthwhile to have a professional landscaper look at it as it will be quite an involved project.

I can never look at a space and decide what shape of bed to put in it, instead what I do is look for limiting factors to decide where the flowers shouldn't go and then use the process of elimination to pick where they will.

Think about paths, views you want to obstruct or create, problems with drainage, slopes, etc. Spend some time wandering around or just standing and looking at it from different angles, you might want to add a sitting area for enjoying the garden when you are done with it.

If it were my space I would want to blur the lines between garden and lawn by changing the shape of the bed and using grass paths throughout, then I would plant something to block the view of the green blocky thing and generally try to create more of a flowing and naturalistic look. Do you need to have a full-on retaining wall, or would it be possible to use clusters of rock and boulder to give support in a more natural looking way?

It's a lot of work, but if you create a blank slate to start with you will have an easier job in the long run. Can you dig up the plants and move them to a temporary holding area until the bed renovation is done? I think you will be happier with the results if you do.

Sorry I can't give you a definite plan, but I think drawing free form beds is the hardest thing of all. I use a hose to mock them up for myself, which you might find useful. Maybe try out some shapes and post more pictures for us to discuss.

Good luck! Keep us updated!

We are considering a dry stream for part of the yard and it would potentially end up in the upper left hand corner of the picture. The area where I am considering the peony bed does not have a large amount of water coming into it. I think a raised bed along there is not going to cause drainage issues as long as it is properly installed. I might need to keep it away from the drain to make sure it doesn't eventually sink in though.

I have had two landscapers (including one company that advertises design setvices) out to give us estimates on work. There are several projects we are looking at having done (patios, dry stream, pathways and retaining walls here). I did not get strong ideas from either one on what to do in this area though. I am still waiting on the estimates.

I have been using some hose pieces, I guess you can't really see them in the photo though.

Here is a picture panning to the left. You can see the same dwarf Alberta spruce. These mangled box elders will eventually have to go but maybe not for another year or two. Eventually the swing will go but for now my kids enjoy it and we don't have a better spot for it. We are taking out or moving the firepit. The area behind the trees accumulates A LOT of water from the back slope and roof run off is directed here. We are considering the dry stream to go from the slope (off to the left) and into this section with it somehow including a rain garden. I hadn't considered extending it farther into the sunny part... I will have to think about that. We already have a long dry bed planned, which all adds up to a lot if rock.

View from the driveway.