I think you're going to want your coreopsis mid way back. The thing with the dianthus is they'll either be cut back down after blooming or if the low spreading type, they'll be deadheaded.
Either way, your coreopsis are way too tall to be in the front.

It does sort of depend on what type of dianthus you grow. The low growing silvery leaved type are usually grown up front since they are so short (though their blooms are tall - kinda). Most yellow flowering Coreopsis are tall enough to be in the middle but the pink to red flowering types tend to flop towards the light and stay pretty low but taller than the matt of dianthus. Also the flopped over coreopsis will shade out the dianthus if you plant them right behind them so give them some space. Though you probably don't want to hear it - most of the people I know growing any of the Limerock series have not had them be foolproof perennials. They tend to look good for a year or so and then must be replaced.

Well crap! lol
I thought they were so pretty...and not yellow, I wanted something a little different.

The Dianthus i'm growing are the perennial varieties Raspberry Swirl and Raspberry Suprize.

I was planning on mulching them pretty heavily....perhaps that will make a difference. If nothing else....I can dig them up and put them in one of the buildings...I have two with nothing in them.

Thanks for your help! I really do appreciate it!

If you like the raspberry colors of the dianthus (and that's what I have also), the other sides of my perennial bed in front have iceplant. Raspberry ALL SPRING/SUMMER/FALL. Full hard after noon sun and no water but rain. I wouldn't mulch the dianthus too much if at all. They don't like wet feet and ice plant you don't mulch either. If your planting area has water(soakers) you could plant the lime colored coleus. That way you'd have the color impact you want and won't lose it as you would when the coreopsis quit blooming or get eaten by bugs.

Oh they would hate coming inside! I think they like the same sort of environment as the dianthus (kinda dry, not so rich soil, full sun) but they just don't last for years and years. I have seen them look stunning with nice healthy clumps a couple of feet wide in one season but it seems that after a year those same clumps start to falter. There are plenty of perennials that require a bit of grooming to keep them looking nice and this is one of them. They are not 'plant and leave alone' types of plants - like the dianthus or the monarda.

Speaking of which - what type of monarda did you get? most of them are really really tall and fast spreading. They also like it a bit wetter than the dianthus or coreopsis but maybe if the soil is rich but kept kinda dry it will slow them down. There are some dwarf forms out there - I know one of the clumps in my garden is a tiny little one with full sized blooms.

You could find a small mounding grass to plant between the coreopsis which would hold them up should they flop for you.

Out at Plant Delights they had a row of Purple Pineapple Lilies (Eucomis 'Sparkling Burgundy' I believe) with Coreopsis 'Limerock Ruby' and some sort of dianthus mixed in and around, it made a wonderful display of pink and purple tones against a silver carpet of dianthus leaves.

I'm just trying to warn you that there are certain perennials that grow to a certain size and then go downhill, so you have to dig them up and divide them in order to keep a nicely shaped clump on display. All the hybrids with Threadleaf Coreopsis seem to be this way. If left alone they don't look so hot after the first summer.

I have the following monarda:
Gardenview Scarlet
Jacob Cline
Raspberry Wine
and Blue Stocking

I planted those toward the back of the bed...but, not completely against the foundation. I thought they would spread and get around 2-3 ft tall.... so I spaced them rather far apart.
I only bought two of the Coreopsis....just to see how they would look. I figured they would get as big as my Pineapple sage and the Blue Black salvia I always get a clump of from my dad.
They are not close together.
I'm going to check out the ice plants...they sound interesting!

I just wanted to say thank you to Dottie.....those Ice plants are GORGEOUS!!!

You're most welcome. It's often forgotten as a no-fuss perennial that spreads and is long season color. Clippings are easily rooted also. My dianthus grows up amid the ice plant area and when the white flowers die back you wouldn't notice the dianthus is even there until spring and (if you've clipped the spent dianthus flowers) again in fall.

Do you have a suggestion for something really tall for the very back of my bed?
I have a small little piece of garden that wraps around my house that is maybe 5x5x5 that I now have canna planted in.

I would really like something that grows upright rather than spreads width wise.....do you think salvia would be a good choice?

I've seen Jacob's Cline and Raspberry Wine get head high, like 5 feet tall. In my dry bed they tend to stay around 3 or less but they don't fill in nicely without the extra water.

Black and Blue Salvia is also a big bush like plant, mine routinely blooms at 5 feet even in the shade.

My experience with salvias has been they grow at least half as wide(or more) as they are tall. That takes up a LOT of room and shades plants that might want more sun.
Is the back of the bed the house wall,a fence or what?(wanting to learn to determine reflective heat/heatsink/airflow)
You might try googling "very tall upright flower for back of flower border"

The black and blue salvia is what I have access to....I might try it!

The back of my border is my house which is made of brick.
I'm trying to figure out how to get some pictures via a slide show on here so you can see my progress thusfar. lol

I'm working on it!

why not consider tucking in your coreopsis plants around your mid-height plants and then planting tall cosmos or cleomes in the back? they'd look real pretty swaying in the wind ...

OP(that's 'original poster') or, we'll call you paradise.
Is that gutter downspout free on the ground or into a drain pipe underground?
There's a nice opportunity there for a rainbarrel of the type that have planters around the top (so you can plant things to spillover and mask the barrel.
That brick wall is screaming for some grouping of either lattice or trellis and in the full sun you can plant mandivilla and bring the color up for more visual interest.
The mandivilla is annual here and you buy it potted and replant it in your bed. If you do that, then you don't take up so much space in a narrow bed with salvias that are all bushy green until they finally bloom. Just an idea.

Oh my, you have a chainlink fence section too..great for a backdrop. Even if you hang some potted trailing 'million bells' in an annual way, you'll achieve the layers of color and a nice visual backdrop for plants in the border that aren't blooming yet.

Wow...you rock Dottie! :O)

I have been trying to find videos on youtube...as well as trying to find some pictures or plans online for help..and, I just haven't been able to find what I am looking for with my type of flowerbed.

My gutter doesn't go underground. Ther used to be pvc pipes making the runoff go out into the gravel driveway, but it was going uphill instead of down grade...so when I was working the bed and took it off...OMGoodness it had clogged up and had the more aweful smell EVER!

I want to try and collect the rainwater...we have higher water bills than power bills in this house believe it or not.lol With the gutter so close to the ground..I thought I'd have to do some deconstruction in order to make it work though.
I hadn't thought about the trellis idea....I have been trying to figure out a vine or two that would stick to the brick itself....

For the small portion of chainlink fencing on the side of the house...I have some Moonflower plants that are almost ready to be planted in the ground that I was going to allow to trail along the fence.
I have some of the 20 cent morning glory seed packets I was going to plant up over there too....I kinda like Morning Glories! lol

paradise, can you take another picture of the front of the house from the street (or from a distance so we get a broad view of what guests will see as they enter the driveway?
Can you make it a 'still' ..I'm looking and I can't seem to pause each photo for consideration.