For Maria Mircheva, sugar pines are the most charismatic trees in the forest.

The largest pines in the world — the conifers reach nearly 200 feet and grow 24-inch cones — dominate a swath of territory from Oregon to Baja California, Mexico, but their numbers have dwindled alarmingly over the last two decades due to an invasive fungus called blister rust. The pines, which once constituted 25 percent of Tahoe forests, now account for less than 5 percent of local trees, Mircheva said.

The environmental advocate wanted to help save the behemoths, and in 2007 she began work as the executive director of the Sugar Pine Foundation. The group restores natural regeneration of the sugar pines, hosting plantings with professional crews and volunteers in the spring and fall to combat the fungus.

They’ve planted more than 60,000 blister rust-resistant seedlings over the last five years.

“We’ve already planted 8,000 trees this spring all around the lake,” Mircheva said. “We’ve been pretty successful. We’re planting the seeds in people’s heads and in the soil. It’s important to restore the forests to their natural density and composition.”

Less than one-tenth of the seedlings planted this year will grow to adulthood, a success rate that Mircheva said is still much higher than in the wild where one seed in 5,000 survives.

And the foundation’s young trees have another trait working in their favor — they’re genetically resistant to blister rust.

Sugar Pine Foundation staff collect green cones from healthy pines in the local forests, plant the seeds and then inoculate the baby trees with the fungus. If 50 percent or more of the offspring from a particular tree lives, the foundation will harvest the parent’s cones and hopefully spread the resistance, Mircheva said. Out of 500 sugar pines tested, 65 proved resistant to the fungus, she said.

About 20 percent of South Shore sugar pines have contracted the fungus, according to Mircheva, and there are even more sick trees on the north and west shores.

The plantings help, she said, but results can be slow. Several 3-year-old pines, less than a foot tall, poked up through the pine needles on the forest floor from a planting two years ago at Zephyr Cove Park. The seedlings are finicky babies than need fertile soil and just the right mixture of sun, shade and precipitation. Sugar Pine Foundation staff encouraged Tahoe Regional Planning Agency employees, who planted hundreds of sugar pines at Zephyr Cove Park Tuesday, to come back and nurture the seedlings.

“If you want to mark your seedling so you can come back and water it, that helps. If you want to name one, feel free,” Sugar Pine Foundation Development Coordinator Tressa Gibbard joked.