About 4,000 down and 46,000 to go: The National Park Service is setting out to give some love to the Santa Monica Mountains by planting 50,000 native trees over the next year, and it could use your help. On most Fridays and Saturdays through April 2022, you can register to plant and water coast live oaks, willows, elderberries, valley oaks and sycamores across the park.