City crews are in the process of adding about a dozen trees to Massachusetts Street and replacing the cumbersome tree planter boxes with more pedestrian-friendly tree grates.

Mark Hecker, a supervisor with the Lawrence Parks and Recreation Department, said crews would be planting trees and removing planters for the next month, as long as the weather cooperates.

Currently, crews are working on four planter boxes at the northwest corner of Eighth and Massachusetts streets. The work has taken eight parking spots out of service temporarily.

Hecker said crews would be replacing trees and planter boxes in locations where trees have died or become diseased. He said there were about 12 locations north of Ninth Street that would be replaced.

The tree grates are slotted metal plates that surround the base of the tree. They will be flush with the sidewalk, unlike the planters, which extended above the sidewalk about 6 to 8 inches. The flush surface allows pedestrians to again use that part of the sidewalk, adding 2 to 3 feet of walkable space.

“It gets a little crowded down there with all the outdoor dining spaces,” Hecker said. “This just gives walkers a little more space.”

As part of a pilot project last summer, the city installed two grates on the east side of the 600 block of Massachusetts Street.

Hecker said the new grates cost about $800 each. He said his department’s plan was to buy a few of the grates each year to use where dead or diseased trees needed to be replaced.

The city has about 400 trees along downtown streets.