Sunny annuals will do just fine there....things like calibrachoa, japanese blood grass, heliochrysm, bacopa....and if you need fillers, stuff like that new Kong Coleus and artemesia will be fine....even petunias will bloom for you if you keep them deadheaded.
Linda C

If the planter is extra deep, you needn't fill to the bottom with soil. Use filler material (non-absorbent, as in plastic bottles, styrofoam, etc.), cover with landscape fabric, then add soil to a depth of 12". You'll have plenty of room for annual roots to grow.

I'd do partial shade plants. I don't think 3 hours of sun, even mid-day sun, is enough for true full sun-lovers.

Some suggestions:

* Heliotrope (I grow in partial shade, and they do very well even though considered a full-sun plant).

* Geraniums (ditto comments on heliotrope).

* New Guinea Impatiens

* Browallia

* Elephant ears/caladiums

* Impatients are a possibility - I'd try a couple as filler plants and see how they do, if they do well then you know you can use them next year.

Even if the plants wilt during the heat of the day, they should perk up again once the shade hits.

If you put landscape fabric ontop of plastic bottles and such, you in a few years will have drainage problems, as the fabric will fill with silt and hold water and you will essentially have a layer of plastic in the bottom of your plantins site and no drainage.
If the afternoon shade comes from the tree line, it's "high shade" and lets through a fair amount of light.
Linda C

Have you thought about using coleus? Some mound, some trail, some are upright, and all have beautiful coloring. I wish I could remember where I was just reading about annual grasses. It sounds like they would be striking in your planter. Have you tried searching Fine Gardening online? Good luck, would love to see how it comes out!

Thanks for all the responses! I miss the days when they got e-mailed to you.

I think Michele (Mxk3) might be right that many super full-sun things won't work. If I had one more hour of sun, I'd feel better about it. Thanks for the list of things you've tried in partial shade. I did think of New Guinea impatiens..I think that might be a great one to try & I'll try some of the others. I wouldn't have thought geraniums would work; that's good to know. I'm also pretty sure true shade things, like the impatiens will totally wilt as this is hot mid-day sun and not gentle morning sun. I can do a little experimenting though and try it as you said.

I guess Linda's right too that it's bright shade in the afternoon..Maybe I'll try a few sun things and stick with the partial-shade stuff for the bulk of it. Again, I can experiment..stick a couple of petunias in and see what happens..

Luckily, dirt is one thing I don't have to worry about. The planter is part of the house & was filled with dirt when we bought it. I think it's rocks at the bottom covered with soil. The planter has holes at the bottom front face for drainage. I'm just going to remove some of the dirt and add some potting soil to lighten it up.

Yes, Tangerine, I'd thought of coleus. Sun coleus, I presume? Will they be okay in midday sun? I'm afraid this year there's little chance my planter will be a balanced thing of beauty. I'll just be happy to have plants that thrive. If I get lucky & it comes out okay, I'll post a pic.

Thanks for everyone's help!
Michele