What do you call that strip of lawn between the street and sidewalk? How about "tree lawn," or "streetscape," or maybe even "hell strip." Whatever you call it, if you live in Denver, you're responsible for its planting and maintenance.
That said, there are many options beyond the obvious choices of grass and trees.
Denver guidelines require property owners put living plants in "normal-sized" tree lawns that are 5 feet or wider. Non-living alternatives - mulches, rocks, and pavement - are allowed only in narrower strips or in commercial corridors. Use care with bark mulches to avoid bark blowing or floating into the street where it can wash with storm water and plug drainage ways.
The plants permitted in normal, wide tree lawns include ground covers, low-growing perennials and shrubs in addition to trees. Many of these also may require little water and maintenance. When planted in mass, they can create a design effect similar to turf.
The heights of shrubs must be low so as not to block sight lines for traffic safety. Vegetation must not block pedestrian or traffic movement. Prickly plants that could present a hazard are discouraged.
Pick plants based on the amount of foot traffic and sunlight. Since the area often includes trees, shade is generally a consideration unless the trees are young. Native, low-water-using grasses such as buffalo grass do poorly in shade.
Bluegrass is moderately shade-tolerant, handles foot traffic well and will grow on 24 inches of water a year, rather than the 35 to 40 inches many people apply.
Some matted ground covers will tolerate light foot traffic along quieter streets. A tree lawn of thyme or sedum performs well in Denver. Walkways and steppingstones are a good idea to provide sidewalk access for people exiting and entering cars. Note that any landscaping projects for residents living on designated historic parkways and boulevards require approval from Denver Parks and Recreation.
An advantage to landscaping tree lawns with low water use plants is that you'll waste less water. Narrow landscape strips are difficult to water efficiently because water sprayed in the air easily blows off-target. The limited target area presented by narrow tree lawns inevitably leads to water falling on streets and sidewalks, leading to runoff and waste.
In using automatic or handset spray heads, be sure heads are properly aligned to wet plants and not hard surfaces. Soak-and-cycle irrigation, which allows water to soak in before applying more, also will reduce runoff. Hand watering, soaker hoses or drip irrigation are efficient ways to water.
Whatever plants are chosen for these areas, keep in mind street trees and their water needs. Reduced watering last year resulted in many stressed street trees showing scorched leaves last summer. Trees stressed last year will be less tolerant of additional stress this summer and special efforts should be made to supply adequate water. (tree-watering recommendations).
Susan Baird, planner for Denver Parks and Recreation, says that since Denver's earliest days, planted tree lawns have provided the aesthetic character that ties neighborhoods together.
"It's the visual rhythm of green trees above that frame a space below, complemented by a continuous, horizontal green tree lawn, that gives Denver its distinctive character," she says.
Baird recommends using masses of silver-leafed and other color plants. "Our modern definition of green has expanded beyond bluegrass to add richness to our urban design," she says.
The chosen plants should match the level of maintenance in which residents are willing to invest. How much and how often will watering be necessary? How will it be applied and what is the time required? Will the plants require mowing, pruning, deadheading, weeding or mulching, and how often?
Take advantage of todays wider plant choices to match plants to your tree lawn conditions and intended maintenance requirements. The result will benefit both your property and neighborhood.
Photo of flowering street strip: Judy Sedbrook
Photos of green tree lawn and low growing junipers: Susan Baird
Photo of watering with soaker hose: Carl Wilson
© CSU/Denver County Extension Master Gardener 2010
888 E. Iliff Avenue, Denver, CO 80210
Date last revised: 01/05/2010