WATERLOO - Sometimes gardeners try too hard.

Of course, who doesn't want to "wow!" garden visitors? We yearn to impress guests with our plant combinations, the mixing and matching of colors, forms and textures to create a symphonic crescendo worthy of Yo Yo Ma. Sometimes, though, it's just noise. It can become too busy, too hectic - sensory overload. Sometimes it's the simplest plant combinations that blow you away.

Several years ago, while touring an extensive Eastern Iowa garden, I saw such a combination. It was simplicity itself, but the effect was memorable.

Dozens and dozens of heart-shaped, ruby-red caladiums were planted in a thick, sweeping circle around a tall shade tree. Encircling the caladiums was a triple ring of pristine white impatiens. The mass planting looked so fresh and cool on a hot summer day, and a pair of white-washed Adirondack chairs was an open invitation to linger beneath the shade. What a scene!

I fell in love with caladiums that day, and I have intermingled a few with hostas in a shady bed. The paper-thin foliage is appealing, and the range of colors available is mind-boggling: Any shade of red, fuschia or pink leaves with green margins, splotches or veining, white foliage with green margins, veining or splotches, chartreuse green foliage with burgundy markings. "Fancy-leaved" caladiums have distinctly heart-shaped foliage. Lance-leaved caladiums have long, narrow leafs on more compact plants.

Varieties include "Freida Hemple," red and green; "Rosebud, pink with green edging; "Carolyn Whorton," pink with red veins and green borders; "Gingerland," white with green and red irregular splotches; and dwarf varieties like "Miss Muffet," chartreuse and burgundy; and "Candidum Jr.," white and green.

Another plant for the mid- to late-summer garden is the stunning new canna, Tropicanna Black. It is a real looker, with purplish-black foliage and scarlet/orange blooms. Thriving in sun or part shade, Tropicanna Black can be planted in the garden, in pots and in ponds and water gardens.

Apparently the plants clump and it offers for to eight blooms per stalk into September. Tucking in a few cannas into a mixed border is a surefire way to add a bit of the tropics, but cannas also play surprisingly nice with other favorite late summer bloomers, such as dahlias, rudbeckia, mums and asters.

Grown in a pot, this canna can reach 4 feet tall; in the garden perhaps a bit taller. I confess I haven't seen it locally yet, but I'm keeping my eyes peeled. If nothing else, I'll put it on my must-have list for next spring.

Canna rhizomes must be lifted in fall. When leaves begin dying back, cut foliage to 4 inches, dig up the rhizomes and let dry for a few days in a protected area, then store in a cool, dry place for winter. In spring, divide clumps and replant after the last frost date.

Caladiums grow from tubers, which should be planted about 2 inches deep with buds facing up. Soil should drain well and be enriched with organic matter. Fertilize with slow-release formula at planting. Water on a weekly basis when the weather turns dry, and don't forget to mulch. In pots, plant to water regularly and fertilize every couple of weeks.

Dig and store the tubers in fall after the foliage turns yellow or after the first frost. Dig the whole plant and let it dry in a warm, dry location for about 1 week. Then cut off the foliage and tuck tubers into a box filled with peat moss. Store at 50 to 55 F.

Or treat the plants like annuals and do nothing. Then you can indulge in new colors next spring.