I love scaevola, and it is great in window boxes. It makes a nice "spiller", tolerates the most horrible heat and humidity imaginable and just keeps on blooming, as long as it gets water. I wouldn't recommend lantana, just because it will be so large that it will just "consume" the scaevola.

Last year, I did my boxes in blue scaevola, yellow melampodium (million bells), and blue salvia, (Victoria). They were lovely all summer long.

This year, I am thinking of using the sedum, Ogon, along with the scaevola as my spillers, just because I like blues with chartreuse.

You could also use it with profusion zinnias (any color: pink, fire, apricot, white), or Crystal Zinnias in either white or orange.

I got some of the burpee zinnia, Highlite, seed this year and it is gorgeous! It looks very much like profusion zinnias, but the blooms are a true yellow with no gold or orange in it. I may use that with the Victoria Salvia and blue scaevola. (Can you tell that I love yellow and blue together?)

I am sure others will have great ideas too. I'll be watching! :)

Madagascar periwinkle can take the heat and comes in various shades on the red/pink/apricot side of the spectrum as well as lavender and white. There are also some that have a darker eye for contrast. There are no yellows, however. Perhaps add a dusty miller for the contrast of its grey leaves?

Another wonderful new plant that I'm now seeing in my local Home Depot and Lowe's is Diamond Frost euphorbia. It looks like baby's breath with abundant tiny white flowers. No deadheading required. It just keeps blooming and blooming. Very heat and drought tolerant.

Also for your consideration is pentas (a.k.a. Eygptian star flower) which is heat and drought tolerant. Again no yellow, just shades of pink, purple, red, and white. You'll probably want to look for a lower growing variety, such as Graffiti which is 12-15" high.

Consider the color of your house and pick flower colors that will look good against it.

How about orange zinnias? (I like orange and purple)

carrie

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On a past thread about favourite container combos, someone had mentioned planting a pot (I know, yours are window boxes but it might work, better to hear all ideas) with the lime-green sweet potato vine, and blue scaveola. They said it was lovely since the bloomed stems of the scaveola peeked and poked through the background of chartreuse leaves of the spud vine.

Last year I had a pot of blue wonder scaveola with a orangey peachey lantana in the middle, the fan flower took over and the color at dusk was almost flourescent (gorgeous) - made me think scaveola is okay on it's own for that punch of colour.

Have fun and post a photo if you can of your final decision.

Cuphea (batface plant), Cordyline 'Red Sensation', Agastache, many Coleus.

Persian Shield would look great with anything lt. blue. I plant it with plumbago and its a great combo.