A little understood enemy is threatening the creek in the Placerita Canyon Natural Area.

A nonnative Middle Eastern plant, it is capable of sucking the stream bed dry and causing fires. It is of concern all over the southwestern United States.

Alarmed, naturalist Robert Grzesiak formed a volunteer nonnative plant removal group. He calls their efforts “native plant restoration” because removing dominating foreign plants allows natives to re-establish themselves.

The group struggles to remove nonnative plants, especially tamarisk.

Grzesiak knew mature tamarisk can choke a waterway. He was determined this would not happen in Placerita Creek.

When fire struck in August 2017, Grzesiak saw a rare opportunity.

Fire had ripped along Placerita Creek through the Disney Ranch and over the Placerita Canyon Natural Area. It denuded the banks of Placerita Creek of its thick, lush blanket of green – making it easy to root out nonnatives, especially tamarisk. There in the dry streambed, thousands of tamarisk shoots were exposed.

Robert Grzsiak, leader of the Native Plant Restoration Volunteers

Grzesiak knew the group had to act. He saw tamarisk’s damage to water flow and native wildlife in the Santa Clara River.

Four years ago, on a 90-mile hike, Grzesiak and fellow ecologists Ron Nichols and Denny Truger walked the entire length of the Santa Clara River from the desert to the ocean.

A retired clinical scientist, Grzesiak took extensive notes of the plant life on the river. One thing he observed was the tamarisk’s green stalks sucking water from the river. In addition, this nonnative plant was capable of blocking flows, causing flooding, and vastly reducing habitat for native animals. He learned of successful eradications of invasive, nonnative plants in Santa Monica and other places.

In the Mojave Desert, following a tamarisk removal project, water actually began to flow again. Native desert animals returned. In the Santa Clara River, the city of Santa Clarita had removed the dangerous plant.

How much easier would it be to take out tamarisk if the mature versions were gone?

A lot.

Longtime volunteer Maria Ellena Christiansen digs out tamarisk.

Now the group would meet to take advantage of the big fire.

On a recent Monday, this writer found Grzesiak working alone, long before members of his eradication group assembled. As they began to arrive, they slowly assembled around him, 12 in all. He reviewed what they had accomplished.

“Today, I want you to focus on tamarisk,” he commanded, waving his hand downstream.

Turning to volunteer Dan Kott, he asked if Kott remembered where tamarisk efforts had left off. As Kott led a portion of the group downstream to resume the previous month’s removal operation, Kott marveled at the number of shallow holes in the stream bed.

“We’ve literally removed thousands of these tamarisk shoots. That’s the power of working together,” Kott said. “The nonnative plants have an unfair advantage. When they are eliminated, not only do native plants come back, but so do native animals that developed here along with the plants which with they evolved.”

By way of example, Knott said native oaks provide shelter and food for 150 animal species, whereas nonnative eucalyptus shelter and serve only 25 kinds of wildlife.

Volunteers think they will see Placerita Creek return to its original state.

Ingrid Brown believes wildflowers will come back as a result of the group’s efforts.

“It will be like Palmdale’s poppy fields. It was once like that around here – carpets of wildflowers like you see in the springtime at Carrizo Plains.”

She is the group’s most faithful member. Brown has never missed a monthly meeting since the group started.

As head of the group, Grzesiak rarely, if ever, misses the eradication efforts.

“Robert often works here alone three days a week,” said Kott.

James Kocham, a Placerita docent-in-training, removes tamarisk from Placerita Creek.

Why is the former scientist so passionate about removing this tree?

“Severe tamarisk infestations will not allow native cottonwood and willow trees to grow,” Grzesiak said. “Tamarisk can extract salt and concentrate it on the surface by way of leaf litter, thus suppressing growth on the surface. Tamarisk does not conserve water like the natives; it loses vast amounts of water through evaporation. It can suck a stream dry because it grows in very densely.

“Since its sap is very salty, it is avoided even by insects and fungi. It is of minimum use to birds for nesting. It can grow so dense that stream beds and rivers become subject to flooding due to blockage during a severe storm. The density of growth makes stream banks more vulnerable to fire. Fire encourages the dominance of the invasive plant because it regrows.”

This writer asked if keeping the park free of tamarisk would be difficult.

“No, since we are removing it early. But it needs to be patrolled yearly to prevent pockets of the plants from re-establishing,” Grzesiak said.

And if the patrolling is not done?

“A mature tamarisk can produce half a million seeds per bush or small tree that can float downstream, or in the wind. Also, the shrub can reproduce by root or stem fragments after flooding,” he said.

A regular check on the Placerita stream bed is essential, he said. “Once riparian plant life (native plants near water) matures, our restructured stream bed will become resistant.”

The restructured stream bed is the re-establishment phase of the project.

That day the group advanced its eradication project about a quarter mile.

“Including this Monday, we have now completed about a mile and three quarters of the 2-mile stream. Monday was our third session on the fire scared creek,” Grzesiak said.

Besides Grzesiak, Brown and Kott, other Placerita Nature Center volunteers that day included Marie Ellena Christensen, James Kocham, Sara Vinceli, Mike Maloney, Cindy Gold, Rob Stark, Henry Cauz, Roger Mclure and Jim Harris.

If you’d like to assist the Native Plant Restoration Volunteers, contact Senior Ranger Supervisor Frank Hoffman at the Nature Center, 661-259-7721, Tuesday-Sunday from 9 a.m. to 5 p.m. The office is closed Mondays.

Jim Harris is a member of the Placerita Canyon Nature Center Associates.