“Hunting for Easter eggs isn’t the only tradition to draw holiday observers outdoors this weekend.Tree planting has become a similarly emblematic ritual for a more secular holiday, Earth Day, which kicks off its 30th anniversary this morning.Since the first Earth Day in 1970, observance of the annual eco-event has expanded to include such actions as reducing personal energy use, eating less meat, and substituting bicycles for cars. But over the decades, tree planting has remained an earth-friendly favorite.The answering machine of Bainbridge Earth Day organizer Michael Sheehan this week confirmed as much.I’ve had a bunch of calls from people, Sheehan said. They’re like, ‘Can we please do tree planting?’Insuring that this zeal won’t go unanswered, park maintenance supervisor Roger Belieu has obtained 700 trees from Puget Sound Energy’s (PSE) Community Forestry Program, which volunteers will plant at Gazzam Lake Park today. The event begins at 10 a.m. at the main park gate off Marshall Road.For three years, park district employees have removed tenacious Scotch broom weeds from the former family resort, and now Belieu hopes to begin to return the site to a natural state.In areas where we were trying to get rid of invasive plants, he said, we’ll be able to reforest that with native species.Volunteers from Americorps and the Kitsap County Alternatives to Detention Group will help islanders plant the park with native douglas and noble fir seedlings, purchased by PSE with a grant from the National Tree Trust. Once the seedlings grow, they will shade out sun-loving invasive species, and help reestablish a native forest.The tree planting should be a festive occasion, organizers said, with free Cliff Bars and other donated refreshments. Bainbridge Gardens will provide additional native plants to set out, such as red twig dogwoods and evergreen huckleberries.For those lacking a green thumb, PSE’s community forester, Jim Trainer, will provide advice, and hopefully improve the survival rate from past years’ planting efforts, said park district planner Perry Barrett.We’re hoping to be closer to 70 percent (seedling survival), Barrett said, but in the past, it’s been a lot closer to 50 percent.Last week, park district employees demonstrated proper tree planting procedure at Battle Point Park, where, since 1978, they have set out more than 650 new trees on the site’s open, grassy fields.A lot of trees sit in almost sort of a bowl from all the clay, said maintenance worker Rob Robinson, as he surveyed a hole destined for a Western Red Cedar, and they die from being flooded.To ensure proper drainage, Robinson lined the bottom of the hole with planting compost, and then set the tree in and covered the roots, being careful not to mound dirt up against the trunk.The young cedar may soon be joined by up to 2,000 neighbors, if Belieu receives a grant from the National Tree Trust to establish a nursery of native trees at Battle Point Park, near the community garden.The park district would use the nursery to replant barren areas, such as Gazzam, and to maintain existing forests, Belieu said. We lose a lot of trees to windstorms, he said. Plus, there’s a lot of diseases like root fungus that jumps from species to species.Maintaining forests and planting new trees is important not only to support other plants and animals, but also to counteract the effects of global warming by converting the greenhouse gas, carbon dioxide, to oxygen, scientists say.Nevertheless, those driving to Gazzam in a Ford Expedition this Earth Day may not realize that it would take the average tree many lifetimes to counteract the global warming effects caused by such a 12-miles-per-gallon behemoth, according to some studies.Thus, Earth Day should be about more than just planting trees, said Mercedes Lawry, deputy communications director for the Seattle-based national Earth Day campaign.We should all examine all types of our behavior and how they affect the environment, she said, from considering what kind of vehicle you drive to changing your traditional light bulbs to energy efficient versions.”