Here are some suggestions:

Spring:

Baptisia pendula (white blooms)
Thermopsis chinensis (clear yellow blooms)
Penstemon digitalis 'HuskerÂs Red' (whitish pink blooms)

Summer:

Caryopteris 'Summer Sorbet' (chartruese var foliage)
Coreopsis 'Full Moon' (clear yellow blooms)
Coreopsis 'Redshift' (butter yellow blooms w/ rosy red markings around the eye)
Eryngium yuccafolium (silvery foliage and flowers)
Leucanthemum x superbum 'Becky'

Fall:

Solidago rugosa 'Fireworks' (yellow blooms)

I would also maybe look for plants that may have bold tropical foliage. Something like Canna 'Bengal Tiger' would look wonderful (except for the orange flowers, but they could be removed if you were so inclined). There are some crinums that flower white and shoot their blooms up to 3' or more.

I have 2 types of Feverfew, one flat daisy-like and the other flowers are like little pincushions. I tend to like the plain one more. Both come up easy from seed and may be thungs under certain conditions but I find with our heat and dry spells they are easily kept under under contol.

How about Rudbeckia Goldstrum? or Coreopsis? I can't recall the variety but it isn't moonbeam - it's the more golden yellow.

I usually just lurk around here but I wanted to say that your garden is beautiful and the first picture made me sigh! Lovely!

I am not at all sure if this plant will work for you and I am absolutely no expert - but I recently got a variegated willow for my purple/pink front yard to lighten things up and I love the brightness it adds to the spot. Good luck!

Mo

Sometimes just the commonest old thing can be just right. What about white Madagascar periwinkles (Catharanthus roseus)? The 'Cooler' series grow pretty tall and there's a solid white and a white with a pink eye if I remember correctly. They won't mind a little shading from taller plants, and will reseed like mad.

Esperanza (tecoma stans) could grow in your garden as an annual. The Texas web sites list it as deer resistant. The yellow Daturas are supposedly deer-resistant. They are stunning from a distance and the color is fairly soft.

What about Chartreuse instead of yellow or white?

Have you looked at lists of natives? I was thinking Silk grass (Pityopsis graminifolia) but I read it is a forage plant. Pretty blue/silver foliage in the summer, yellow flowers in the fall, but they'd think it was part of the buffet, I guess. It grows wild here and they don't eat it up, but there may just be other things they prefer here.

Nell

For yellow, how about achillea 'Coronation Gold'. Clear yellow flower. It gets to be at least 3 ft. tall (maybe a little more). Extremely drought tolerant. Has a very long bloom time. The flowers are easily dried for inside arrangements. I don't know for sure about deer and rabbit resistance, but mine have never been bothered by either. Will rebloom if you cut them back. Easy to divide. Have I missed anything?

Achillea 'Gold Plate' is another yellow option. It does, however, get to be @5 ft.

Liz

Coreopsis Full Moon is a hardy, taller variety for our area. I have lots of clumps from one plant I bought last year. It's claim is 3" blooms, but I'm about 1.5" short of that both years I've had it. Maybe next year?

Do deer like hibiscus? Red Texas Star would really add some height. Luna series can be grown in with the other perennials. And don't forget shasta daisies. Alaska grows 4-5' for me.

I have plenty of baptisia seedlings that I can move for spring! Light blue, but free!

I have three caryopteris 'Longwood Blue' and two 'Snow Fairy'. The foliage of the snow fairy looks great, but it hasn't bloomed well for me. I also had 3 of those die out. I didn't see any of the chartreuse foliage ones at Southern States or a few other places, but I will keep looking as I love those.

I have coreopsis 'red shift' -- that's with the burgundy gaillardia in the butterfly garden. First summer with those, so I'll see how they overwinter. I have 'Creme Brulee' up in front, but it's very short. Haven't seen 'Full Moon'.

Penstemons did well here for one year, then they were eaten by something. Not sure what -- maybe rabbits or the deer developed a taste for them.

I thought deer would eat erynigum and shasta daisies? If they don't eat shastas, that's good news! Those would be great. I have two echinops that have similar foliage to erynigum. The deer don't eat the blooms, but they'll eat the foliage to the ground after I deadhead.

Mums are supposed to be deer resistant, so I need to find some of the tall ones. Bluestone sells those only in spring.

Feverfew reminds me that my bronze fennel is blooming lots of yellow flowers right not over in the butterfly garden.

I have a lot of Rudbeckia 'Goldsturm' in the butterfly garden and have started some in the front garden. It's not visible yet out front. Plenty to go around, but the rabbits eat it like candy unless I spray repellent on it. The rabbits eat the sides off and the deer don't eat the tops, so it looks like umbrellas!

I have a lot of yellow achillea and am waiting to see if it will rebloom since I cut it back after the first bloom. I've started the terracotta over in the butterfly garden, too. It's very pretty.

Deer like tropical hybiscus, but so far, they've left my Rose of Sharon alone. It's still a new shrub for this year.

... all good suggestions and many of which I can do by moving plants around from the butterfly garden.

.........

What about:

white centranthus ruber?
ironweed?
culver's root?

Anyone have success, experience with those?

I planted so many white cleome, green laceflower to fill in this void.

I don't know why I got only 3 laceflower plants and NO cleome! It could be that my DH thought they were both weeds and he's quite the weeder! I had to go around and pick up marigolds and cosmos seedlings one day and replant them! LOL

Cameron, when looking up whether Dictamnus albus was deer resistant I found this list, probably a lot of these have already been mentioned but might be worth a look see.

Annette

Here is a link that might be useful: Deer resistant Plants

I thought deer would eat erynigum and shasta daisies?
I can't speak for other gardens, but the deer have never touched either one of these in my garden.

Mums are supposed to be deer resistant
Unfortunately, this has not proven to be the case in my garden. They will leave them alone until the flower buds start to form, and then, they get munched on like candy.

What about:

white centranthus ruber?
ironweed?
culver's root?

I haven't tried the white valerian (centranthus), but I did try to grow the pink, and it was one of the most anemic plants I've ever tried to grow. I've read that they like alkaline soil, so that may be the reason why. Mine certainly never looked like the ones in the magazines did.

I grow Vernonia arkansana (received years ago from the arboretum plant distribution), but I think any of the ironweeds are very easy to grow and do well here.

I have a little beef with culver's root. I like it, but this plant really likes the moisture (typically more than I can give it) and the foliage really degrades after it blooms.

Moonbeam with Golden Jubilee Hyssop. It should be taller. Even last year's plants were taller. But I divided that plant into 12 new clumps this spring. That could have something to do with it.

The agastache is a first year plant too, a self-sown baby. I know it will be bigger next year.

I like it the way it is. Correction: I LOVE it the way it is.

Don't know about rabbits, but deer are supposed to leave these alone:

Mexican Mint Marigold (Tagetes lucida)
Augusta Duelberg Salvia, the white version of Henry
Copper Canyon Daisy (Tagetes lemonii)
Wormwood (Artemesia 'Powis Castle')

Mexican Feathergrass (Nasella tenuissima) would be nice, too, though it may not be tall enough for you.

Once again, it is lovely to look at your garden.

I cannot personally attest to their deer resistance (although they are on the list linked to above) but how about tall white Balloon Flower? It can get to close to three feet, but better yet, it can handle some shade if you have changing conditions down the slope. It is a bright, crisp white that I think would complement your existing plantings.

Good luck with your decision!

So beautiful!

Some of my yellow and white deer resistant flowers/plants are Helianthus (Perennial Sunflower), shastas, feverfew, lamb's ears, yellow yarrow, dusty miller, and rue.

Some others from the site below are Basket of Gold (Aurinia saxatilis), Ligularia dentata, white bleeding heart, broom, shrub potentilla, foxglove. Not sure how they are in your zone.

Here is a link that might be useful: deer resistant plants

I love the way your garden looks, especially in photo 2, but if you want some changes, then go for it. I can't guarantee all of these can take your full sun, but they are deer-resistant and I think bunny resistant. We have some rabbits in the neighborhood--I see them all the time--but pretty much all the damage I get is obviously from the deer.

White swan coneflower--I really like it, I'm wondering why you aren't sure it'll look great? I bet it will.

Tall, yellow, fairly big blooms:
Heliopsis, summer sun (golden yellow double) or lemon queen (lemon yellow, very tall) or others. There are also a couple of short ones. Summer sun is 3.5 ft for me.

Coreopsis grandiflora, a tall version like Tetra Giants (I'm not sure which mine is): mine has blooms that are about 1.25", golden yellow, gets 3-4' tall.

I've heard the yellow species echinacea, I think it's Echinacea paradoxa, is a tough plant, not like the hybrids made from it.

Is there a white monarda that is tall enough? If not, it may stretch to compete with neighboring plants just fine, I think mine do stretch in fruitless hopes of getting more sun.

Agastache: there are a couple of yellows, one is hardy only to zone 6 or 7, one is hardy up here. I just got the zone 5 one this year, A. nepetoides, so I may have seeds in the fall. It grows to 7 feet and photos of the blooms look light yellow to white.

There is also agastache golden jubilee, which has chartreuse foliage to lighten the scene.

The deer almost never touch my shastas. I've had shastas for 4 years, and the only chewing was last year on my supposed crazy daisy seedlings. They left them, and all the others, alone this year. They leave my eryngium completely alone.

My deer love to eat mums, and asters, and maximilian sunflower, just about anything that blooms in the fall--except goldenrod. I think they leave that completely alone. Montauk daisy is nibbled early but usually left alone in fall.

My deer leave the "red" Centranthus ruber alone, as well as Culver Root. I haven't grown Ironweed yet. Verbena hastata also has branchlets and violet flowers, and is deer-resistant here. My mom's red Centranthus in almost all-day sun is upright, although a bit floppy. Mine, in ok sun, was totally floppy and I gave it away. I don't give my Culver's Root any extra water, maybe I should. It does fine, but is not spreading.

Did you direct-sow the cleome? I had no luck with cleome the first couple of times. When I dumped a lot of fresh seed straight into the garden in autumn, I finally got sprouts in spring.

I've been out moving things around because rain is in the forecast. Time for lunch right now...

I can see a lot of great suggestions here that I'll have to come back and read tonight.

I was so mad that I was spitting nails this morning! My gaillardia 'Golden Goblin' youngsters turned out to be plain old burgundy/gold... AGAIN! I'm not buying anymore plants that aren't in bloom in the nursery! I've been fooled twice. Won't happen a third time.

THANKS!
Cameron

I tried Chapel Hill lantana last year for the wonderful primrose yellow, huge spread and low height. It was fabulous, especially next to Walker's Low catmint and small crimson pigmy barberry. It;s supposed to be hardy to zone 6, but it didn't come back this spring. I think it was a victim of the clay and my cutting it back incorrectly. I plan to try it again.

I planted Chapel Hill lantana and the main plants did not return. However, recently I noticed little yellow -- and orange --- lantana kids sprouting from that spot in the garden. I have it planted with salvia 'black & blue'.

Nervy of me to make any suggestions for your glorious garden.
However, I look at it like art and to me it's not necessarily just light your missing, but lack of darks are just as important here, if you want more pizzaz. In art, I am always working for the contrast. Avoiding sameness in form , texture and tone (even though you have different colors, they are pretty much the same tone--intensity), automatically helps avoid the boredom--"tired of looking at"--as you say.
See what a beautiful contrast the small shrub, at the far end, adds. I would repeat that in a couple of places. It would not only encourage the eye to travel, but it would make your lights look lighter and bright pinks etc. look brighter when planted in front of it.
I don't know most of these zone 7 plants, but I do grow the Husker's Red penstemon (white bloom, blousy, long blooming perennial) and it would be beautiful here.
All that being said, I think it is wonderful as is in the calming, non-contrast design. It all depends on your goal.
gramma jan