ON MILD spring mornings, Sunnyside residents Eileen and Matthew Walsh can be found digging up weeds at a small community garden not far from their home.

The garden, which opened two years ago this June, is the only discernible patch of green amid a landscape of paved streets. It's also a memorial to those who lost their lives on 9/11, including the couple's son, firefighter Michael Brennan.

"Just to think that he'll be memorialized forever and people will know his name - it makes us feel close to him," his mother said. "No matter what, you can't change what happened, but you see things blooming, and it's a really warm feeling."

The L.I.C. Roots Community Garden/Firefighter Michael E. Brennan Memorial is having its third annual plant sale starting today.

Anyone can become a member of the garden for $5 a year. All proceeds go toward its maintenance.

Before the plot of land became a living legacy, it was intersected by rusting railroad tracks and served as a parking lot.

Noah Kaufman, a city worker and gardener, and other community leaders decided there was a better way to use the vacant lot.

"There was a need for environmental restoration, and the city hadn't caught up with that," Kaufman said.

To create an open space for residents and students from nearby schools, Kaufman founded the nonprofit group L.I.C. Roots Inc. in 2003.

He knew that Eileen Walsh, who worked at the adjacent Robert F. Wagner Jr. Secondary School, was grieving the death of her son. Brennan, a member of Ladder Co. 4, died at the World Trade Center.

"It just made sense to commemorate Michael's bravery, as well as so many other innocent people," said Kaufman, chairman of the group's board of directors.

Volunteers from Brennan's firehouse helped tear up the cement. With support from the city Parks Department and the Council on the Environment of New York City, the garden officially opened in 2007.

"It's getting prettier each year, and it's a reminder that a lot of good can come from something tragic," said Eileen Walsh, who is now treasurer of L.I.C. Roots.

The plant sale and membership drive will continue until Wednesday at lunchtime.

The garden is at 47th Ave. at 30th St., in Long Island City.