According to the Barbara Stein, author of Noah’s Garden, a perfect lawn perpetually requires intensive inputs due to the fact that it is completely cut-off from the natural system that would otherwise support it. Additionally, the roots that grow from lawn grass become a “feltlike mat” that is between 2 and 4 inches deep. The tangled roots inhibit the growth of other plants and require large amounts of water input during the hot summer months, as well is 5 “feedings” of nitrogen, phosphorous and/or potassium. With so many inputs, including additional herbicides to remove any potential invaders, the grass grows rapidly which requires that it be cut frequently which in turn encourages the growth of new blades because the plant is never able to flower. In turn, the carrying capacity of the lawn extremely low because there is a lack of biodiversity that is necessary to support fauna.
As grass has evolved to endure grazing it grows sideways below the reach of grazers (or lawnmowers) in order to protect the nodes from consumption and/or destruction and the tillers of the plant grow from the root of the plant, as opposed to the stalk itself. Furthermore, grass is defensive in nature – there is silica in the blades, needled awns in the seeds, and the ability to use leftover nutrients in the roots in order to toughen the cellulose in preparation for the following growing season. There is also an indication that different grasses “green” sequentially as an adaptation to grazers.
As a result of these adaptations, grass looks best in the spring because that is when it is naturally vibrant, has had enough time to “rest” and it is not going against its natural cycle of “tanning” and relaxing in the summer when the weather is hot. It is suggested that an inch of water be applied to lawns along with various fertilizers, herbicides and pesticides in order to maintain the youthful, green spring glow. These inputs need to applied because “lawn” grass engages in C4 photosynthesis which incorporates CO2 with a 4 carbon compound. This form of photosynthesis takes place in the inner cells and occurs much more rapidly than C3 photosynthesis under high light intensity and temperatures because of the compound PEP Carboxylase delivering the CO2 more rapidly. C3 photosynthesis incorporates CO2 with a 3 carbon compound. This form of photosynthesis takes place in the leaves and is most effective in cool and moist locations with normal light conditions.
For more information on the effects of chemical inputs, check out this post on eutrophication.