Things are about to perk up for the trees that line Massachusetts Street.

Their dry branches will sprout green again, and passers-by will walk in cool shade, hearing fresh leaves shifting in the wind.

Linden, fruitless ginkgo biloba, Japanese tree lilac and rosehill white ash are the species that spruce up the landscape. Lindens make up the majority of the trees up and down the street. Ginkgos grow in the newer raised planters near the ends of the block, like the ones in front of Round Corner Pharmacy, 801 Mass., and Teller’s, 746 Mass. The tree lilacs accent the corners, and ash grow near the crosswalks in the middle of the blocks.

Because most of these trees now grow in confined concrete planters, the Lawrence Parks and Recreation department employs special strategies to keep them healthy.

In a park, a tree’s roots sprawl out two to three times the width of its crown, or the outline made by its branches, says Rod Croucher, downtown field supervisor for the city’s horticulture division. In concrete planters, however, roots can spread only minimally, so landscape crews must prune the trees accordingly, keeping the height and width of the tree’s shape in conjunction with its root system.

“It’s a balance,” says Crystal Miles, horticulture manager for Lawrence Parks and Recreation.

Adequate water is a concern, too.

“You’re dealing with a big pot,” Croucher says, so it dries out faster. Crews during the summer water the trees twice a week, depending on temperatures and drought conditions. They also use mulch, which helps keep the base of the trees moist.

But the “main ingredient is water,” Croucher says.

Healthy leaves

In the early 1970s, the city planted rose hill white ash trees in the concrete planters, which were built during the installation of parking spots along Massachusetts Street.

“They were a design element that came with saw-tooth parking,” Miles explains.

But nowadays, those trees aren’t faring well in their downtown environment and have been prone to diseases caused by insect infestations. Borers and microscopic spider mites have caused unsightly growths and cracks in the bark.

“They’re kind of a trashy tree,” Croucher says of the ashes.

The city has decided to phase out ash and bring in ginkgos as replacements, which have proven disease- and insect-resistant in the area, Croucher says.

The city is also phasing out concrete planters as they replace dying trees to make the sidewalks more accessible for pedestrians. A metal grate will cover the base of the tree and be level with the sidewalk.

With the exception of the ash, downtown trees are tough and can handle being planted around streets and sidewalks, where human and automobile traffic is high, says Scott Wisdom, sales associate at Sunrise Garden Center, 1501 Learnard Ave.

Trees are field-tested across the United States and Canada to see which ones do best in different climates, Croucher says. Through trial and error, horticulturists find out which species do better in certain conditions, and that’s how people like Croucher choose which species to use.

Antonio Mateos, of Lawrence, rests on a bench in downtown Lawrence next to a tree surrounded by bricks that create a planter. Lawrence Parks and Recreation crews employ special measures to care for downtown trees, many of which grow in concrete planters and, soon, metal tree grates.

Downward spiral

The trees downtown usually live for 15 to 20 years, growing a little each year. Some are still around from when the city started planting them more than 30 years ago. These over-the-hill trees are scattered throughout the area, but passersby can see some of them in the 800 block of Massachusetts Street.

Trees get old just like humans, and as they reach maturity, they start to decline with age. This process speeds up with trees in the planters because they can’t grow as they would in an open space.

“Mature size is directly related to soil volume,” Miles says. Just as humans’ bones get brittle and organs wear out, trees stop growing and become more susceptible to disease.

“Insects will come in when they sense the tree is stressed out,” and Croucher says.

Stressful times for trees include drought and extreme heat. Injuries like broken branches from rowdy humans or lightening strikes can also cause the tree to start declining. Although insects cause diseases that damage trees, different factors play into how fast a tree declines and eventually dies.

“Everything depends on the roots,” Croucher says.

For instance, trees may be damaged when they are moved into a confined space like the concrete planters, or the metal grates the city is in the process of installing.

Each year, the city replaces about 5 percent – 15 to 20 – of the more than 300 trees downtown, depending on circumstances.

Money well spent

The Parks and Recreation department buys field-grown trees from local and out-of-state wholesale nurseries for about $150 a piece. The labor and equipment costs run about the same, bringing the total price of installing a new tree to around $300, Miles says.

Trees lend aesthetic appeal to the environment that we sometimes take for granted. When Kansas temperatures crank up in late summer, Massachusetts Street would be a lot hotter without the shade that the lindens give. Trees also add color to the downtown landscape when the tree lilacs release their white flowers in spring and the ginkgo turns gold in fall.

Diverse factors play into the recipe for growing a healthy tree. The city does its best to keep the trees downtown thriving, and a seasonal crew devotes its time to taking care of them.

Croucher says, “We leave (them) as long as we can.”