Why Lawn Grass Is Not Green

From an aesthetic or ecological point of view, a lawn is preferable over concrete, stone and asphalt. The latter trio absorb light energy but then slowly re-radiate as infrared, adding to the heat-island effect of urban areas. Grass instead keeps things cooler. While growing rapidly and absorbing carbon dioxide and water, it invests a fair amount of light energy into the bonds of cellulose. If mulched when mowed, its carbon conditions the soil.

But what’s wrong with grass in the city? Most lawns in temperate areas of Europe and North America consist of Kentucky bluegrass. To be kept in a juvenile state and to be given a competitive edge over plants of the C4 variety, lawns leave behind a deep ecological footprint: they have to be watered, fertilized, mowed and weeded.

Few take measures to conserve water and electricity by relying only on rain and using a manual reel mower. Only a minority use compost instead of synthesized fertilizer, which is energy-intensive and which can lead to runoff and eutrophication. And in most neighborhoods, people don’t get on their hands and knees to remove plantain, dandelion and other “weeds”.  Instead they reach for herbicides, some of which contain glyphosate, a probable carcinogen.

We can learn from history, as researched by the authors of this Calgary website. The popularity of lawns is historically rooted in status—they first became fashionable among 17th century English and French aristocracy who were the only ones financially capable of hiring others to maintain the luxury. Kentucky bluegrass and Bermuda grass became adopted only in the 19th century when people did not realize the shortcomings of  “monoculture”.

Why can’t lawns be an example of biodiversity and showcase a variety of low-growing, low-maintenance plants? Many plants that normally grow taller will succumb to the selective pressure of an electric or manual mower and will even flower when only a few centimeters tall. Legumes such as black medic, white and red clover fix nitrogen from the air and require need little or no fertilizer. Thyme and oregano, which generally prefer well-drained soils and are ideal for sloped terrain, need less water than grass. Young leaves of maligned dandelion actually make a good addition to salads. Species of stitchwort and wild violets produce small but subtle flowers.

Ralph Waldo Emerson lived at a time when lawns became popular. Yet he realized that “a weed is a plant whose virtue is not yet known”, a statement quite consistent with his transcendentalism. Our surroundings could bring out our better nature. Ecological lawns could help urbanites become more environmentally responsible.