PROS' PLANT TECHNIQUES KEEP DOG DAYS AT BAY

By CHRISTINE ARPE GANG

While home gardens languish in the late summer heat, commercial plantings seem almost as vibrant as they were in June. What secrets do commercial landscapers keep under their sun visors?

Turns out there's no mystery. Their success boils down to good horticultural practices, grown-to-order plants and access to the latest information.

Underneath every good looking commercial flower bed is an irrigation system that keeps plants well-watered.

Adjusting these systems is a challenge because overwatering can be detrimental, especially to petunias and periwinkles.

Commercial landscapers also make use of slow-release fertilizers to give plants enough food for the season.

As a general rule, no plants are set into the ground until the soil is a well-draining, friable mix. That's accomplished by amending the clay soil with coarse builders sand, sphagnum peat and finely ground bark.

"Landscapers also tend to plant closer together with larger plants," said Carol Reese, ornamental specialist at the University of Tennessee's Experiment Station in Jackson, Tenn.

Instead of six-pack sized flowers, they tend to choose annuals in pots at least 4 inches in diameter.

"They know how to put colors and flowers together," said David Levy, owner of Willow Oaks Farm in Brownsville, Tenn., a producer of bedding plants for retailers and landscapers. "You can give two people the same plants and one's may look good and the other's doesn't."

Commercial landscapers also select their plants more carefully than home gardeners. Most contract with wholesale growers to get the best cultivars available, many of which may not be available in retail garden centers.

"I go for heat and drought tolerance," said Don Pafford, operations manager for Adsit Landscape and Design Firm in Memphis.

It's not enough to decide to plant petunias in the spring. You need to have an idea of the kind of petunias you want  spreading, trailing or mounding.

In commercial settings, annuals installed in May must continue to look good until October, when they will be replaced by pansies. They may be professionally maintained, but there's no time for pampering.

And while there are always individual preferences, a number of annuals are on almost every landscapers' list of top performers:

The Yubi series of portulacas in yellow and rose have bigger blooms that seem to stay open longer than other varieties.

"They love the heat and don't set seed," said Steve Cohan, vice president of Environmental Landscape Services in Memphis.

"We put these in the second week of May and they've been blooming ever since," he said referring to the portulacas in planters at the Ridgeway Inn in Memphis.

Pafford also likes Sundial portulacas that come in a wide palette of colors including mango and two shades of gold.

Planted with the yellow portulacas at the Ridgeway Inn are Purple Wave petunias, petunias prized for their spreading habit and persistent flowers. Wave petunias are also available in pink and lilac.

Petunias in the new Madness series, such as Sheer Madness, are more compact but just as prolific as Wave.

Profusion zinnias, especially the orange ones, are favored for lasting blooms and a compact size. The red or Cherry Profusion loses its vibrant color in the heat.

Lantanas have long been selected for their heat tolerance, and now there are some more compact varieties.

Pafford likes Yellow Samantha for its variegated foliage. Reese likes a new lavender variety.

Several of the landscapers have compliments for setcreasea or purple heart, a dark purple-foliage plant that occasionally shows tiny pink flowers.

Cohan thinks it's been overused, especially in mass plantings without other flowers to foil the strong purple color.

Coleus and caladiums are typically suited to shade gardens, but new varieties are sun-tolerant.

Cohan places the tall deep red Burgundy Flame coleus at the back of a bed layered with other annuals at the entrance of Ridgeway Terrace Apartments.

Carolyn Whorton, a white caladium with a red vein, cools down a sunny bed.

Celosia, especially Prestige Scarlet, has such great red foliage one hardly notices its less significant plumes.

Scaevola is favored for its spreading blue fan-shaped flowers. It stays low enough to form a cooling ground cover.

Joseph's Coat, a chartreuse foliage plant that forms small mounds, is being used more by commercial landscapers than home gardeners.

Cohan uses Scarlet Prelude, an effective edging plant, with begonias.

Ornamental grasses give motion to the landscape as they wave in the breeze. In the winter their amber blades glisten in the sun.

"I find the dwarf pennisetum are the best," Cohan said. "The miscanthus get too big."

But at the Gables Apartments in eastern Memphis, landscape designer Michael McClain uses several large ornamental grasses in the expansive lawn. He likes to use dwarf versions of maiden and fountain grasses in mass plantings.

These days it's difficult to imagine the summer urban landscape without masses of sweet potato vines, both the black (Little Blackie) and chartreuse (Marguerite) versions. Both are rampant spreaders; the chartreuse will stretch out 20 feet if not clipped occasionally.

Luckily, they die at frost so we don't have to worry about another kudzu on the horizon.

Lisianthus, cup-shaped blue and purple flowers, are surprisingly heat tolerant, said Reese, who grows numerous annuals in field trials every year.

Gomphrena or globe amaranth also do well.

Melampodium with its small, yellow, daisy-like flower and light green foliage is also heat tolerant.

Torenias, the tubular blue to purple flowers, are best in partial shade.

Vincas, also known as periwinkles, were once the iron horses of the garden. But recent hybrids tend to rot when exposed to too much water. "They are good for places that don't have irrigation," Cohan said.

Because perennials have shorter bloom periods, they are not used as much in commercial plantings as annuals that flower all summer.

But Cohan likes the large-petaled rudbeckia, Indian Summer, paired with purple petunias. "They bloom a long time and then come back next year," he said.

McClain likes Indian Summer, too, as well as the smaller Goldsturm. "I love perennials," he said. A dwarf buddleia (butterfly bush) that reaches only 3 feet tall, purple coneflowers and perennial salvias are among his favorites.

He's also been planting more tropicals such as alocasia and banana trees for their bold foliage.