Members of the Liz Christy Garden, at Bowery and East Houston St., celebrated the 40th anniversary of the city’s first community garden. There was the famous hat party, with this year’s winner sporting a chapeau in the shape of a watering can. There were free hot dogs and nonalcoholic drinks, and a band played. Founded by legendary greenthumb Liz Christy, today the lush swath of foliage across from more recent arrival Whole Foods Market is home to an eight-story-tall Metasequoia, or dawn redwood, the biggest example of the tree in the city. Dawn redwoods were once thought to be extinct, but a former Liz Christy gardener, today only recalled as “the soldier,” brought back a seeding from a remote area of China where a stand of the stately trees was discovered.