It’s been three years since the crew for the Wallis Annenberg Wildlife Crossing Native Plant Nursery set up shop in Calabasas, with dozens of difficult-to-assemble metal tables, a spartan trailer and a million native seeds hand-collected from the surrounding hills.

That’s three years that nursery managers Jewlya (pronounced “Julia”) Samaniego and Jose Campos have nurtured thousands of native plants from seed, despite plenty of rattlesnakes, hordes of pot-gnawing squirrels, the vile smelling essence of cougar pee to repel the squirrels, blistering summers that required twice-a-day watering, even on weekends and holidays, and a couple winters of mud, erosion and endless rain.

A man and a woman walk under shade cloth through tables covered with native grasses and plants.

Jewlya Samaniego, right, and Jose Campos, co-managers of the Wallis Annenberg Wildlife Crossing Native Plant Nursery, grew more than 5,000 native plants from seeds hand-collected from the hills around the structure. Over the next few weeks, those plants will be moved from the nursery and planted on the crossing in 10-by-10-foot grids. (Al Seib / For The Times)

Now it’s graduation day, when native plants coaxed from seedling trays to 1-gallon pots stand ready for planting on the crossing itself this month.

“It feels like going off to college,” said Samaniego, a slender mother of four whose oldest is in the throes of college planning. They’re ready to go and you want them to go, she said, “except, ‘Wait, are you sure you’re really ready?'”

Ready or not, the 5,000 or so plants have to go because the wildlife crossing over the 101 Freeway in Agoura Hills is ready to receive them, with its special, once lifeless soil that was brought to life with inoculations of the same microbes and mycorrhizal fungi that thrive in soil of the surrounding hills. After the soil was added this summer, workers seeded the ground with a cover crop of native plants particularly good at kick-starting that fungi: Santa Barbara milk vetch, golden yarrow, California poppy and giant wild rye.

Four people walk past tables covered with native plants in the rustic outdoor nursery in Agoura Hills.

In the late summer and early fall, many California native plants are brown and dormant, but they’re still very much alive and will soon be planted on the wildlife crossing, where they’ll grow and bloom come spring. Here, nursery managers Jewlya Samaniego and Jose Campos give crossing overseer Robert Rock and junior landscape designer Makala Gibson a tour of the 5,000-plus plants they’ve grown from seed. (Al Seib / For The Times)

Those seeds have sprouted and grown on the crossing these last few months, especially the milk vetch, but they’ll be cut back to just a few inches this month to stress the plants and encourage the fungi to produce even more nutrients in the soil to help them out.

“We don’t want to introduce salt-based chemical fertilizers, so you have to continuously rely on them,” said Robert Rock, chief executive of Chicago-based Rock Design Associates and the landscape architect overseeing the $92.6-million project. “We want to rely on natural chemicals in the soil, like from our cover crop, which jump-starts that natural nutrient capacity of the soil.”

Samaniego and Campos have always consider their jobs to be more than just raising plants in a nursery. They had training with native plants from Antonio Sanchez, manager of the Santa Monica Mountains Native Plant Nursery, and then Katherine Pakradouni, the first manager of the wildlife crossing nursery who collected the first million seeds on five-mile foraging hikes around the nearby hills.

But the emphasis on building soil microbes was new to them, Campos said, adding: “I had the idea we were doing some restoration work, but this is basically restoring the land over the freeway. We’re kind of rebuilding nature.”

Rock, Samaniego, Campos and a few other associates met at the nursery Monday to load up about 30 plants from the nursery to prepare for Tuesday’s planting ceremony. Samaniego, who has Indigenous Chumash and Tataviam ancestry, planned to wear regalia of the Tataviam people, whose historic home ranged from the San Fernando Valley to the Simi Valley as far east as Antelope Valley. Other longtime supporters of the project would get a chance to plant during the first official planting from the nursery.

Tall brown stalks of native wand buckwheat are bare, except for tiny balls of pink flowers.

Summer dormancy has turned the tall stalks of wand buckwheat brown and bare, except for tiny balls of pink flowers, but the plants should leaf out again in the spring. Al Seib / For The Times

The red, deep-throated flowers of California fuchsia.

The red, deep-throated flowers of California fuchsia typically don’t appear until the late summer and early fall. These plants go dormant in the winter. Al Seib / For The Times

The celebration is one of several events planned this week during Urban Wildlife Week, culminating on Saturday with the 10th anniversary of P-22 Day, a free festival from 11 a.m. to 3:30 p.m. at Griffith Park, the one-time home of L.A.’s famous cougar.

During Monday’s preparation, Diego Banda, CalTrans principal assistant resident engineer for the wildlife crossing, helped carry plants up the steep steps to the top of the crossing 75 feet above the freeway. Then he and his team helped Nadia Gonzalez of Puente Strategies, the project’s media coordinator, lay down plywood boards to minimize soil compaction during the ceremony, while Rock, Samaniego, Campos and junior landscape designer Makala Gibson dug holes for the plants chosen for the ceremony: bush sunflower, California fuchsia, more Santa Barbara milk vetch, California aster and purple needle grass.

The nursery is growing a lot of other native plants too — white sage, toyon, buckwheats and other sages, to name several — but Rock said many of those plants are looking ragged right now after summer dormancy. “It might look like we’re planting dead plants, and that’s hard to explain to people,” he said. The plants that were chosen for Tuesday’s ceremony look greener, he said, and have more visual appeal.

As the plants for the ceremony were being pulled from the pickup, Rock rescued a little frog stowaway from the nursery and carried it to the top of the crossing, releasing it near a section made muddy by the temporary sprinklers.

A man in cap carries four plants in gallon pots out of a pickup.

Jose Campos, co-manager of the Wallis Annenberg Wildlife Crossing nursery unloads four pots of native California asters for planting on the crossing. Al Seib / For The TimesJewlya Samaniego, left, Robert Rock and Makala Gibson watch Jose Campos dig a few more holes for a planting ceremony on Oct. 21 on top of the Wallis Annenberg Wildlife Crossing. Al Seib / For The TimesA tiny frog that had been living at the Wallis Annenberg Wildlife Crossing nursery hitched a ride to the crossing on Oct. 20, on plants that were being brought in for planting the following day. The confused stowaway tried to hop away onto the freeway, but project overseer Robert Rock rescued the frog and released it at the top of the crossing. Al Seib / For The Times

The frog is the second nonflying critter spotted on the crossing. Back in June, Beth Pratt, California regional executive director of the National Wildlife Federation and leader of the Save LA Cougars campaign, who is overseeing funding and fundraising for the project, spotted a Western fence lizard basking in the sun at the top.

Rock said it will be at least another year before the crossing will be connected to the Santa Susana Mountains to the north and Santa Monica Mountains to the south and opened to wandering wildlife.

Stage 2, the most complicated and difficult part of the crossing project, began early this summer, but the work has been barely visible except from the top of the crossing or along Agoura Road on the north side of the freeway. Crews have been moving water lines and soon, they will bury power lines along about 175 feet of Agoura Road to make way for a tunnel that will cover the road and support a small mountain of soil, connecting the crossing to the southern hills.

Already, there are weekday traffic delays on Agoura Road as a giant drill bores a line of deep holes on either side of the road. After each hole is drilled, a crane slowly lifts a 70-foot-long wire straw called a rebar cage and, inch by inch, lowers it into the hole. Once in place, the cylindrical cage is filled with concrete to create a foundation for the concrete wall and roof of the tunnel.

A tall crane rises above Agoura Road and the Stage 2 construction on the south side of the wildlife crossing.

Construction on the south side of the Wallis Annenberg Wildlife Crossing involves drilling deep holes for concrete pilings that will serve as the foundation for the 175-foot-long tunnel that will cover Agoura Road and support the small mountain of soil that will connect the wildlife crossing to the Santa Monica Mountains beyond. (Al Seib / For The Times)

The wildlife crossing was built in precast sections, brought in from Perris, Calif., to limit freeway closures, Rock said, but the tunnel work on Agoura Road will all be poured on-site. The goal is to keep traffic moving with periodic daytime closures as long as possible this fall, he said, but by the end of this year, when the main tunnel construction begins, the road will have to be closed entirely for the safety of the workers and drivers.

“We’re doing our best to reduce the impact to the community and not do full closures until they absolutely have to,” Rock said. “But people use that road as a short cut and they’re accustomed to zipping through there. We’re letting people know they need to slow down.”

The tunnel construction likely will stretch from the end of this year until early summer, he said. Then will come the huge job of moving soil from a hill on the north side of the freeway, created when the freeway was built in the 1950s, to cover the tunnel on the north side and connect the crossing. But that earth-moving work likely won’t start until the late summer or early fall.

“People see the site now and they don’t think progress is being made,” he said. “But we have to start first with the non-sexy pieces of construction: utility and foundations. Then you’ll start seeing the visual transformations.”

In the meantime, Campos and Samaniego have been collecting more seeds around the hills because once the plants are emptied from the nursery for the crossing, they must start planting a much bigger batch of plants, including oaks and other native trees, to cover the shoulders of the crossing once the soil is in place.

It’s a lot of work, Samaniego said, but a task they’re eager to start.

Jewlya Samaniego and Beth Pratt at the Wallis Annenberg Wildlife Crossing.

Jewlya Samaniego, co-manager of the Wallis Annenberg Wildlife Crossing Native Plant Nursery, and Beth Pratt, California regional executive director of the National Wildlife Federation and leader of the Save LA Cougars campaign, were among the project’s supporters invited to plant the first of the 5,000 native plants grown at the nursery during a special ceremony at the crossing on Tuesday. Samaniego planted a Santa Barbara milk vetch on the left, and Platt put in a bush sunflower. (Jon Kopaloff / Getty Images for #SaveLACougars and the National Wildlife Federation)

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This story originally appeared in Los Angeles Times.