Gardeners call it the "hellstrip," that skinny bit of often-neglected grass sandwiched between the street and the sidewalk. Now, some are sprucing it up, transforming it from perennial eye-sore to showpiece.

Homeowners in cities and towns across the country are seeing opportunity in these plots—also called "parkways" or "tree beds." They occupy choice real estate in front of a home, potentially contributing to visitors' first impressions, not to mention a resident's own view beyond the edge of a well-tended lawn.

In Medfield, Mass., Betty and Neal Sanders have planted tough perennials such as Joe-pye weed and creeping junipers in the strip between the sidewalk and the street. Channing Johnson for The Wall Street Journal

Even diehard gardeners find, though, the strips of land—surrounded by concrete and asphalt—are subject to challenges including road salt and snowplows, foot and bicycle traffic, sniffing dogs and wayward trash.

Betty Sanders has lush gardens on two acres in Medfield, Mass., but every time she pulled in or out of her driveway, the strip in front of her house gnawed at her. "It just looked ratty all the time," she says.

So, she and her husband recently used compost and shredded leaves from their own property to plant flowers in similar shades of blues and yellows that echo the rest of her garden. Now, "it's a garden that introduces the rest of my property," she says.

Whether or not they are technically part of a homeowner's property can vary from city to city, even neighborhood to neighborhood. Homeowners are typically responsible for basic maintenance, like mowing, whether or not they legally own the property. Regardless of ownership, the strips are typically in the "public right of way," meaning that homeowners have little recourse against passersby who trample on the petunias, says Eduardo M. Peñalver, a Cornell University law professor who specializes in property and land use issues.

A view of Francis Michael Dawson's home in Santa Maria, Calif., before he transformed his hellstrip. Francis Michael Dawson

A view of Francis Michael Dawson's home in Santa Maria, Calif., after he transformed his hellstrip. Francis Michael Dawson

In Takoma Park, Md., Jackie Braitman saw the weedy strip in front of her home as a chance to visually lengthen her small front yard and create "more of a sense of welcome," she says. While the strip is technically owned by the city, she chose to do something fairly elaborate, planting two pink-flowering crape myrtle trees on the strip directly across from two crape myrtles on her own property. The effect is an "allée" for pedestrians, she says, as two sets of tree limbs reach towards one another, forming an arch over the sidewalk. Beneath the trees, Ms. Braitman, an architectural designer, chose plants that can withstand heat and other stresses, and that still have attractive foliage even when not in flower. Many of these plants are repeated in her own yard—such as coral bells (heuchera), Thunberg spiraea (Spirea thunbergii 'Ogon') and "Knock Out" roses.

She spent about $500—most of which went towards the cost of a professional landscaper who put in the trees, which were about $100 each.

Some gardeners see in these plots an opportunity to experiment with plants that they couldn't otherwise get to grow in their own yards. Ellie Dorritie, a retired postal worker in Buffalo, N.Y., says the full sun exposure in her planting strip allows her to garden with different plants than what she can get away with in her much shadier yard.

Her garden scheme? "Cram it in," she says. "I ask, 'Does it bloom? Will it fight for space?' If the answer is yes, it goes in."

For the most part, she says, neighbors are respectful and appreciative. There was one tiff a few years ago with cable company workers who wanted to dig up the plot for an installation. After a few tense words, "they gave in," she says. While the entire sidewalk was ploughed up in order to make room for fiber-optic cable, "they didn't touch my strip," Ms. Dorritie says.

In response to what some city officials see as growing enthusiasm for gardening in hellstrips, a number of municipalities are offering more latitude for planting in them, while still requiring that certain rules are met.

Seattle last year removed its permitting requirement for gardens in "planting strips." Homeowners must adhere to certain plant height restrictions: Plants can't exceed two feet near an intersection; areas within 10 feet of driveways must be clear of plantings that block the view for motorists and pedestrians, says Rick Sheridan, spokesman for the city's Department of Transportation. While he isn't aware of any specific accidents related to overzealous gardening in the strips, his office has received complaints about plants obstructing views at intersections, he says.

In California, Santa Monica says it supports "parkway" plantings, though the city technically owns the plots, as long as certain height requirements are met. Residents must get a permit before planting anything more extensive than a few annuals, says Russell Ackerman, a specialist in the city's Office of Sustainability and the Environment. In the last two years, his office has offered grants of up to $5,000 for homeowner water-efficient landscaping projects and most of those applications include plans for parkway planting as part of the total makeover, while about a third are focused on just the parkway, he says.

"Space for gardening can be limited because we're a dense urban area," says Mr. Ackerman. "Some people really latch on to that parkway and plant it up."

Horticultural experts issue a few warnings to enthusiastic hellstrip gardeners. Jennifer Britton, assistant professor of landscape design at Montana State University, cautions against planting vegetables because of contaminants that can run off the nearby road.

Nina Bassuk, program leader of the Urban Horticulture Institute at Cornell University, says gardeners should make sure that their hellstrip planting doesn't interfere with established trees. Trees play an important role in urban areas, she says, for providing shade, mitigating stormwater runoff, and helping improve air quality. So be careful when shoveling near root systems.

Some gardeners say they like the social aspect of gardening next to the sidewalk. "I spend a lot of time out there futzing," says retired anthropology professor Jane Adams, "and I got to know everyone. The kids would stop and tell me how much they enjoyed it." Her space in Carbondale, Ill., is filled with wildflowers such as cone flowers and tickseed.

Write to Anne Marie Chaker at