Photo by  Richard Maack Durango’ yellow marigold, multicolored portulaca and yellow golden fleece flourish in an oversized container.

Lil’s design Tips
• Arrange plants in clusters to produce masses of blooms, using various colors, heights and textures. Lil Cashman likes to combine spiky pink pentas, soft dusty miller and trailing cup flower (Nierembergia).
• Plant in groupings of three or five and never in a row. If you buy six-packs of flowers, break them up: Mix three from one with two from another.
• Always include a touch of white. It adds punch and stands out in the moonlight. Angelonia, cup flower, pentas and portulaca, which do well in the heat, all can be found in white.
• Consider growing some of Cashman’s favorite summer annuals: red and orange zinnias, coreopsis and gaillardia; purple floss flower; yellow marigolds and golden fleece; and Salvia guaranitica ‘Black and Blue’. She also uses perennial lavenders, pink and red sages and salvias, and purple-blue ruellia, sometimes to create blooming second layers.
• Learn by trial and error. “I have a long list of reliable heat-tolerant flowers. But I’m still trying new ones,” says Cashman. “If they don’t work, I pull them out, go to Home Depot, and start over.” One of last year’s experiments was treating hibiscus as an annual. She used 1-gallon specimens to anchor her pots, even though she knew they would grow too large for the containers. “For $3.99, I had a beautiful plant that bloomed all summer.”
See Sources.