You haven't said the house is symmetrical, and even if it is you don't need symmetry but rather balance. I'm not clear on why you've chosen to divide the yard into "designed" and a "plant collector's" halves. You can design with special plants, integrating the two objectives. And you wouldn't be the first one to begin your design process with the plants you have or want. But what does catch my attention is the word "perennials". It may have escaped your attention that there are a lot of very special plants to collect in families like conifer, Japanese maple, and rhododendron ( you may curse me when you find out how much money can be spent on those plants :-)). I frequently recommend that people take a spin around the conifer forum to get an idea of the world of dwarf conifers. I started with perennials too, but am finding them much less gratifying and less amenable to being designed with as my interest in overall landscape has escalated. What you're after with plants like that is "bones", which is something you can do with hardscape as well. To post a photo, you could check out the gallery side, and put a link to it here in this thread, or you post from a Photobucket or other photohosting site. What you want to put into the body of your message here is the html code, starting with something like KarinL

Imagine that ... landscape maintenance NOT the most important thing in your life and you only have two jobs and 2 kids! :-) When rejuvenating shrubs like this, you cannot cut them back to where they would have been cut as part of routine maintenance (about 30" height, or so.) When they've been let go and you are trying to regrow them, you must cut them back much farther (down to about 12" to 18") and then re-grow them again as if they are new shrubs. If you don't cut them back hard like that, there will end up being unmanageable woody parts that somehow always end of being in the way. It's better to bite the bullet and just get these things out of the way in the beginning. Then begin trimming/shaping the hedge as it's coming back. With most plants that are used as hedges, you will have no trouble getting them to regrow. However, DON'T DO THIS NOW! Wait until between February and just before they would leaf out naturally in the Spring ... which is quite a large window of opportunity. If you do it now, they may produce some growth that will end up just getting frozen and lost. If you do it during the winter, they will not leaf out until the proper time, so nothing will be lost.

I'm not sure I've explained myself properly as to the requirement for professional help. The reason why professional licensure is required for civil engineers, surveyors, and landscape architects is that certain matters, like grading and drainage, are highly technical and have the potential to impact the health and safety of the public if not executed correctly. Stormwater runoff can be a major source of property damage and water pollution when not handled properly. I'm concerned about several things the original poster has mentioned, including drainage swales that were originally designed to drain stormwater off the property that for some reason are no longer functioning. If it's true that significant soil deposition has occurred (as opposed to just some buildup of vegetation, lawn thatch etc. which needs to be cleared off) then you have a VERY serious drainage problem that needs to be professionally addressed ASAP. However, you would not expect to see stormwater handled on a site like this without some drainage structures that connect to the municipal sewers or stormwater drains. This is why you see drains in lawns and planted areas - for any given quantity of rain falling you can only expect a certain percentage of it to soak into the ground (there are standard reference values for this) and the rest has got to go somewhere and not be allowed to go sheeting off into the street, into your parking areas, onto the downslope neighbor's property, etc. It seems maybe more likely to me that standing water, mushy ground etc. as described are occurring because landscape drainage structures are not functioning than because such significant changes to the surface grade have occurred that entire swales aren't working any more. But this is a guess on my part. You may just need some drains cleaned or you may need a major overhaul of the landscape drainage. There could, of course, have been a design or installation problem from the outset but a later failure of maintenance, again, seems more likely. I would look at all these factors before you undertake any surface grading, which may be unnecessary or counterproductive. If regrading the site does need to happen, you must be aware of your municipality's requirements for a grading permit. These requirements vary a lot from city to city, but they are usually triggered by grading projects that will disturb more than a certain number of square feet of surface and/or displace more than a certain number of cubic feet of fill. Lots of other specialized requirements in various places, depending on floodplains, slopes, proximity to foundations, permeable surface requirements, tree protection (where there are tree ordinances), stormwater discharge, etc. etc. Look on your city's Web site to start with: they may have all the requirements posted or just a general guideline. Grading permits may require a variety of plan drawings to be prepared and stamped by a licensed civil engineer, surveyor, or landscape architect. If you do wind up needing a lot of work on the drainage infrastructure then you'll need an engineer as landscape architects' scope does not normally include that.

@DC Water runs down hill. It's best to keep the water at a high elevation, then you are in a better position to find a lower place to discharge the water. I'm assuming the natural drainage from your neighbor is toward your house on the side in the photos. In that case you will need to try to route the water around the house. Backfill the trench with non-permeable soil compacted so that water stays on the surface. The suggestion to waterproof the foundation was a good one. See if you can grade the soil next to the house so there is a downward slope to carry the water around the corner of the house. A retaining wall may or not aid you in getting the correct grading. If you need a wall less than 2ft tall, consider poured-in-place concrete. Cheaper and less skill needed for DIY.