Salt-worthy flowers are stunning—and sensible

Agricultural Research, August, 2004 by Erin Peabody

A flower grower in the Coachella Valley of southern California looks doubtfully at the water easing its way down his field's irrigation furrow. He's using reclaimed drainage water, but he suspects it's infused with multiple salts and trace elements--rendering it unfit for his just-emerging, tender crop of ornamental sunflowers.

Use of lesser-quality waters is common practice for many growers in the water-deprived western United States. But these waters, often recycled after use on other crops, may contain dissolved salts and ions that can hinder plant growth. Compounding the problem is that many growers and nurseries along the California coast must also contend with seawater intrusion into neighboring flesh groundwater sources.

Because of the difficulties facing farmers and growers in accessing high-quality water, researchers with the nation's premier salinity research facility--ARS's George E. Brown, Jr., Salinity Laboratory in Riverside, California--are working to find crops that can endure degraded, often saline, groundwater and wastewater without suffering stunted growth or other salt-induced problems.

A scientist who's investigated salt-tolerant, or halophytic, crops and plants extensively is Catherine M. Grieve, plant physiologist and research leader of the Plant Science Research Unit at the Riverside laboratory. For more than 20 years, she's been evaluating the salt-hardiness of a wide range of grain, orchard, and vegetable crops.

More recently, Grieve turned her attention to floricultural crops--the bright and dazzling flesh flowers that make their way into decorative vases, wedding chapels, and well-groomed backyards. And she's discovered an attractive bouquet of options for growers. Many of these floral crops do tolerate water loaded with salts, and some even appear to be fond of it.

A Pretty Plan

Research into salt-resistant flowers stemmed from an initiative started 6 years ago to bring relevant ARS research to the country's fast-growing floricultural and nursery industries. Second only to corn and soybeans in terms of U.S. cash value, these businesses--many small and family-owned--are busy greening up American streets and backyards. But, while prolific, the industries face a host of nagging problems--from damaging, exotic insects to diminishing water resources.

In California, where cut flowers and foliage for bouquets make up a $300-million-a-year industry, growers are having a hard time accessing their most precious resource--water. Demand for high-quality water continues to increase through competition between urban and agricultural users. This means growers may need to rely more on low-quality water resources. This water, sometimes recycled two or three times, can accumulate high levels of dissolved salts and ions.

Growers along the California coast have another hurdle. Seawater intrusion, in which ocean waters trickle into adjacent underground freshwater sources, has become a problem in southern California. These saline waters get pulled into local aquifers as wells and groundwater supplies are overdrawn.

The laboratory's research into floral species that can withstand waters high in salts or other ions and produce viable, commercially acceptable flowers should help growers to conserve resources, cut costs, and become more efficient.

The environment and public would also win. Reusing greenhouse effluents for cut-flower production would reduce discharge of fertilizer, inorganic salts, and pesticides into streams, rivers, tidal pools, and other sensitive areas.

The researchers' strategy is smart, but not new. Centuries ago, farmers in the Middle East dealt with salinity by replacing salt-sensitive crops, such as wheat, with more salt-tolerant ones, like barley. But while many studies have focused on vegetables and grains that can tolerate salty waters and soils, little work has been done to investigate salt resistance in flowers and nursery crops.

Not All Waters Are Created Equal

One of the researchers' first projects was to create different kinds of water. Specifically, they had to decide on the compositions of waters used to irrigate flower species of interest.

Producing water with a particular chemical profile was the job of soil scientist Donald L. Suarez, director of the salinity laboratory. He's an expert at predicting changes in the chemical composition of increasingly saline waters.

Salts play an important role in plant development. Too much salt may stunt growth, or even kill a plant, while some salt compositions may lead to nutritional deficiencies.

This was a critical step in the research because the water available to growers in different regions of the state varies in its makeup. These differences result from geology, geography, and other factors. For example, waters found in the state's lower, inland valleys of Imperial and Coachella differ from those available along the coast.

"Well water that's contaminated by seawater intrusion contains more sodium and chloride," says Suarez, "while concentrated Colorado River water, existing as reclaimed drainage from other crops, contains relatively more magnesium and sulfate."