I would start with some shrubs and go from there. Not real tall but something for a foundation.

I'd grass it over and move the bed somewhere else. The new bed would be planted much more densely, and include some plants with serious height and mass. Helianthus 'Lemon Queen' comes to mind, or some of the larger ornamental grasses.

I'm thinking you need some kind of hardscaping, rocks for instance, and/or some type of statuary to plant your perennials around. I'd also make the edges of the bed more flowing (a garden hose is a good guide to use) something to edge the bed, to make it look more finished. Then I would find some shorter plants to put on the outer edges, to vary the heights of your plants.

I agree with tasymo with the hardscape. I would get some landscaping stones - natural or man-made - build a higher circle around that tree and plants hostas or other shade tolerant plants. Then I would put a lower wall - straight or flowing whatever your personality is along the yard side. Then (of course it could be pricey)get some height in there. Balance the other end with an ornamental tree, maybe even two since you have sooooo much space. I have lots of ground flox that is beautiful color in the spring and then adds a nice green carpet in the spaces between plants the rest of the season. But you definitely need taller things - even a birdbath or maybe some hollyhocks or other tall plants - a clematis with a trellis???

The first thing that I would do is put a nice sharp edge on the bed along the grass side. A good edge makes a bed look neat and carefully planned.

Next, I would seriously think about edging the whole bed with a low hedge. It's a box - play that up. As the hedge grows and fills in it also covers/hides/detracts attention from a lot of problems.

Since height is the basic issue, I would use a perennial that can be sheared, something like Santolina, Teucrium, Germander, Iberis (Candytuft), or Aurinia (Basket of Gold). I have had good luck in my zone 5 garden with Santolina (only marginally hardy for me) on the outside edges of raised beds with the corners done in Candytuft and Aurinia.

If your garden conditions are right, short sedums might be an inexpensive edging/hedging choice, since almost any stem would root for you and shearing would not be necessary. You could check out ones like the blue/grey Sedum sieboldii (6-12in), reddish Vera Jamison (1 foot, but sometimes flops open), or the warm yellow variegated Sedum alboroseum Mediovariegatum (listed as a 2 footer, but only growing about a foot in my clay, forms a nice rounded upright plant for me).

There are lots of taller sedums, but my Autumn Joys and the newer Maestro (a sport of Matrona) get really tall in good garden soil. Also, it's just a guess, but I think that a shorter edge will make the other plants look taller than they are, somewhat hiding your height restriction problem.

This sedum idea really depends on how much you like sedum and how much sedum you like. You might try mixing and matching some of the shearing plants up with some sedums at your local nursery and see if you get a combo you like, then using the sedums in shorter runs or for structural impact in certain areas.

I would stick with just a few types of edging plants to make the area more unified.

If you wanted to, expecially since it's a large area, you could also divide the inside of your garden into sections or shapes. Lots of Parterre ideas are available online and in books.

Remember though, that even relatively informal hedges, such as I have suggested, are WORK. You could start with a perennial hedge on just the grass side towards the center and see if you like the effect, before spending a lot of time, effort and money on the idea. You can then divide or take cuttings from you existing plants and spread them across and down the sides over several seasons.

Also you could easily incorporate the Dianthus that you mentioned into this garden. They are nice low plants that like good drainage. I am especially fond of the Chedder Pinks like Firewitch which form dense mats of bluish foliage. There are lots of other varieties, but the matting forms (versus the grassy ones) also plays into that guess/idea of mine that you need layers.

A caution though - keep the Dianthus away from your grass - I have a really bad infestation of grass in some of mine along my grass path, which I just can't seem to eliminate. In fact I would keep your entire edging/hedging planting at least a foot away from the grass edge and keep that area heavily mulched.

Some of the sedum groundcover ones such as Dragon's Blood or Angelina are pretty short( 4-6 inches), very colorful in bloom, and spread easily. They could be used to carpet the interior of the bed, lessening the too much mulch look.

Another possibility are Thymes. I'm especially fond of wooly thyme, a very low blue-green mat forming thyme. This can take some moderate amount of stepping on which might be nice along a driveway. Lots of other steppables out there in the marketplace, even one using the term as a brandname.

When I want to plant a larger-growing new plant in my garden I do not hesitate to simply dig a somewhat larger than usual hole (to give the new plant some breathing room)in the middle of my thyme or tear out a bunch of Dragon's Blood sedum and plant directly into these groundcovers. The removed bits can be patted into the ground somewhere else and usually take well with no extra care.

A good edge and some strategically placed pots of creepers might give your garden a finished look and play well with your hot color scheme.

What a great bed you have to plant flowers, and the people passing by will have something really pretty to view.

Great ideas from all.

leslie197 - would you be able to post photos of your garden? I am sure greenfreak and I could get some great ideas, as well as other viewers. I am also changing my garden to have less daylilies (100s), and more perennials. Since it is large, I am very much interested in ground covers to eliminate so much mulch and weeding.

greenfreak - Here are some of the perennials/trees I have in my established garden, I have a 'little house' potting shed, a fountain, a red dogwood tree, an hydranga tree, a Japanese maple, daylilies, several varieties of hyssop, coneflowers, a few roses, a geranium, monkshood, beard tongue, etc. and the ever pain-in-the-back weeds. I also plant some annuals if there is a need to bring some color to an area.

Thank you. Jane

Agree with Mad Gallica: grass it over and move the bed about six feet back from the curb. . .with a full-sun street-side garden, my choice would be heavily mixed ornamental grasses, with just a few ornamentals that compliment them:
Helianthus 'Lemon Queen', Rudbeckia maxima, Eupatorium purpurem, Monarda
'Jacob Cline', etc. - and you could always use the daylilies at the base of the larger grasses

Thank you to everyone for your suggestions! I realize I should have given you more details on the space, but didn't want to overwhelm with information.

mad gallica, I can't add too much height because I am bound by the visibility of the corner, my town's code, and my conscience since this is a school bus stop. I do need to keep my planting low. I have other areas I can add height which I've planted shrubs in.

I do intend on adding mass; call the existing plants the "bones" of this bed. I purposely left large spots between the daylilies and other flowers to add more as I go. I buy the daylilies at a society sale by the tuber each year and don't really know what they will look like until they bloom, so there are always a few that don't "go". I think I will transplant those somewhere else over time and clump like colors together.

tasymo, I agree that it needs some focal points and a rounded edge. After considering edging, my husband and I finally agreed on composite bender board to create that edge and I purchased it last week. I have neighbors who like to park next to my house so I keep a few feet from the street clear for foot traffic (since we have no sidewalks) and for the snow and ice (mixed with salt) that gets plowed there in the winter.

daylily dreamer, I have power lines right above this bed, and do want another ornamental tree but it would have to be no more than 20 feet high. Our town tends to massacre the trees that grow in and around power lines and both the cherry on the corner and another dogwood I have are in danger! Phlox is a great idea! I didn't even think of that. It's a nice small base too that I could build on and add varying heights behind it. Thanks. :)

leslie, wow! A lot of suggestions I really appreciate. I would have to amend for sedum since this bed tends to be heavy but that's no problem. I could do that, and I do like me some sedum! I've always wanted to try dianthus and thyme also. Since there is foot traffic on this bed, I think the thyme would be better served on the outside by the street. Not that I like that people walk there but the kids in the neighborhood might like it.

Jane, I agree, I love photos to get ideas. I guess you have the daylily bug like I do; I think I need to transplant some into other areas, since I have another 50x20 foot full sun bed to work with! Thank you for your suggestions. :)

carl, thank you also for your suggestions!

Just a couple of shots to show you the progression of this bed, in the 1 1/2 years we've been in the house. I'm really at the very start of my garden, so I have lots of time to take all your suggestions and put them to work!

The previous owners had let the corner go, for privacy's sake, but the corner was dangerous and the town requires 75 feet of clear view from the corner. This certainly didn't cut it:

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Lots of maple saplings, privet hedges, poison ivy, poison sumac, and wild roses in there. Since they were starved for light, most of the saplings were pretty leggy and growing through the utility lines above.

We had them clear most of it, looking for something to salvage. All that was semi-healthy was the cherry tree and a dogwood:

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We wanted a dog in the worst way so we had a fence installed (again, low, due to town restrictions), cleared the weeds, had it mulched till we decided what to do with it, then started planting things; dayilies, ornamental grass, spirea, euonymus.

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So that's it! Inside that fence I have more young shrubs that can provide some privacy over time; purple smokebush, viburnum, mock orange, beautyberry.

Thank you again for your suggestions, you've given me a lot to consider! :)

Janepa,
If you click on leslie197 in the Posted by line you should get my profile telling about the garden and a half dozen pictures. I also recently posted some in the shade combos and the Rozanne combos posts. I am moving more into shade plants as my garden ages. Most of the trees and shrubs were planted more than 10 years ago and the perennial gardens were started one by one after that with a lot of work done in the 2001, 2, 3, 4 etc. LOL. It is on a small suburban type lot and is absolutely packed with plants and bulbs. Most of my pictures are from 2005 and 6 when I was first active on Gardenweb. The "basic bones" plantings are now squeezing out some of the perennials. Haven't posted much lately until I got the bug again.

Greenfreak,
You've done a great job so far. Clearly out the mess there on the property edge was a nice improvement and you will surely enjoy your shrubs as they grow bigger. Watch your grasses - some of mine are so huge now that they block access and pathways - try digging a 5 foot diameter grass out of a solid block of clay.

As for the sedums, I grow mine on very heavy soil. Some work, some don't. Raising them up (sometimes and inch or two helps) and adding gravel helps. I must do this for many plants, almost all silvery foliaged things and anything in the High Country catalog, agastaches, salvias etc.

Didn't you say your garden is also a school bus stop? How about a bench to add hardscape and a place for the kids to sit? Then maybe some stepping stones. That way it would be obvious to them where you wanted them to walk.

Thanks leslie! I know what you mean! I have a monster hydrangea right in front of my front steps and if I didn't prune it each year, I wouldn't be able to get in the house! Last year it was almost to my eye level and I'm 5'10"!

I left the ornamental grasses 5 feet on either side and will probably break them up before they got that big. I see big, beautiful miscanthus all the time but I just don't have a large enough property to warrant one somewhere!

daylily dreamer, that's a really nice idea. Someone around the block from me did that, they have a four person bench on their corner. Since it's not a 4 way stop, I worry about the kids standing around in the street. Maybe I'll do that!