Water-wise mats case study

Obra Verde Growers, located in sunny, dry Southern California, is no stranger to water conservation. In fact, the nursery’s focus on producing solely drought-tolerant liners raises the stakes.

“We have to be sure that we do not overwater, because a lot of these plants, when overwatered, will get chlorotic or get soilborne diseases,” says Joe Walker, Obra Verde’s co-founder. “A lot of these are almost considered to be desert plants and they can get into all kinds of trouble if you overwater them.”

Obra Verde is a wholesale liner operation that propagates 100 percent of its more than 100 varieties in 38-cell liners. Walker says the nursery grows a lot of extreme drought-tolerant natives of South Africa and Australia and a few from New Zealand. In fact, Obra Verde Growers has an exclusive agreement with the Department of Agriculture and Food, Western Australia (DAFWA) and the University of Western Australia (UWA) at Perth to release and market the newest and best hybrids of waxflower developed in their research station. The resulting varieties are only available in North America from Obra Verde. The California nursery supplies large wholesalers and smaller nurseries with plants that can thrive in the Western U.S.

“Most everyone we sell to turns around and finishes them in 1s, 3s, 5s for the industry,” Walker says. “They are fairly tolerant to temps, extremes and lows. We like to specialize in varieties that have some timing on color or have extremely colorful foliage to give accents to both landscape yards and the ornamental industry.”

The company works with its own line of plants as well as different breeders, running trials for companies like PlantHaven and Star Roses and Plants.

Whether it’s their own varieties or the breeder trials, everything must be drought tolerant. Obra Verde keeps moisture levels extremely low, both to test the plants and to conserve water. In the last year, Walker has experimented with a WaterPulse capillary irrigation system, and he’s been quite pleased with the results. The WaterPulse system is designed to maintain plants in containers, ranging from large, single-plant containers to propagation trays. The key feature of capillary action is that the soil will only draw up as much water as it can use.

In a trial based in one of Obra Verde’s greenhouses, Walker immediately noticed a 50 percent reduction in water use. But that was just the beginning.

“When you’re saving water, you’re also saving the time and labor of watering by hand,” Walker says. “You’re seeing a 75 percent increase in savings in labor because someone turns the valve on, comes back 15 minutes later and shuts it off instead of standing there with a hose and watering for 20 minutes per bench. It’s been quite a savings for us.”

In addition to saving on water and labor, plant health has improved on benches with the WaterPulse mats. Walker says the way water is brought up through the plants via the capillary action has reduced the frequency of waterborne diseases. He’s cut fungicide usage and says his staff is doing a lot less drenching and sprenching.

Obra Verde has noticed a few unexpected benefits, as well. For instance, in areas where the nursery was still handwatering with hoses or waterwands, the inevitable overspray drips down through the benches, which leads to weeds. And the weeds provide a nice, moist environment for fungus gnats to live and breed. However, this phenomenon didn’t exist under the beds irrigated with WaterPulse mats, Walker says.

“Where we were using the mats, we have no weed problem at all,” he says. “I didn’t even notice until we were a couple months into using them. It’s also really knocked down the problems we used to have with fungus gnats that would get into the weeds down below.”

Obra Verde sprays on a preventive basis, not curative. The nursery typically sprays the crop, walls and below the benches — everything. In areas where the WaterPulse mats have been installed, they have been able to eliminate spraying under benches.

Walker has also noticed improved uniformity. To be sure, his staff doesn’t have to work as hard to achieve even growth as they would with overhead irrigation.

“On a bench, I’ll have 15 to 20 different varieties,” Walker says. “They all are getting the same amount of water, and their growth is very even per variety compared to overhead watering. We’re also finding there are no dry spots. It’s 100 percent moist when it draws up from the base. You’re not seeing the splashing you sometimes get with overhead watering.”

He also says his liners are finishing 25 to 30 percent faster on benches equipped with WaterPulse mats. Because the plants never go into stress from underwatering or disease, they constantly have what they need.

“You can take the tensiometer and do readings from one end to the other and they all read the same,” he says. “You do that with a hose or waterwand device to water, and you’re not going to get that.”

Incorporating the mats into his growing operation was easy. Walker says he spent about 30 minutes per bench for the install and setup. The benches don’t need to be 100 percent level; the water still goes where it needs to go. Filtering the system before setup is an important step that can save the user maintenance later. If a grower needs more water or fertilizer for a particular variety, an injection system at the WaterPulse head unit can be set up. Everything is controlled via in-line valves off the manifold. Walker is planning to expand his use of the system at Obra Verde.

“Any time we can get a faster finish time or cut down on labor in any way, that is all very important,” he says. “Water use has gone way down. All of those factors add up to profits.”

Matt is managing editor of sister publication Nursery Management magazine.