It's hard to overstate the impact lawns have on American ecosystems. In 2005, NASA published the results of a
study that found "lawns – including residential and commercial lawns, golf courses, etc. – could be considered the single largest irrigated crop in America in terms of surface area." The immense amount of land and water dedicated to turf grass makes good management practices crucial.
One of the most disastrous effects of poor turf management is eutrophication. Eutrophication occurs when nutrients enter waterways spurring population explosions of aquatic organisms, like algae. Algae blooms on the water's surface block sunlight from reaching bottom-dwelling plants. In addition, as the algae die, the process of decomposition depletes oxygen in the water, leading fish and other animals to suffocate. The impact of eutrophication has been so devastating in some parts of the country, like the Chesapeake Bay, that many states have enacted strict guidelines for lawn fertilizer applications.
By adopting a holistic approach to lawn care, the High Line horticulture team has been able to keep the grass healthy without relying on chemical fertilizers, pesticides and herbicides. We started with a mix of perennial rye and tall fescue grass varieties that can handle heavy foot traffic. Because root depth mirrors stem height, we mow at 2 ½" to promote root development. With deeper roots, the grass can access water several inches down, reducing water use. Leaving the grass a little higher also enables it to shade out most weed seedlings. The few weeds that do pop up can easily be pulled by hand.
One of the biggest challenges of maintaining a lawn used by tens of thousands of visitors is compaction. Compaction causes the pores in the soil to collapse and prevents oxygen, water and organisms from moving through the soil. In the summer and fall we aerate the lawn mechanically. We also add compost and compost tea to boost nutrient levels and encourage populations of beneficial soil organisms. The movement of these organisms helps aerate the soil. They also cycle nutrients and help protect the grass against pests and diseases.
By managing the lawn organically, we meet the human desire for open, green space, without posing a threat to the other creatures that share our immediate and broader environment. The High Line's design integrates turf into a dynamic planting that hosts an array of other life forms. In this way, the needs of humans are balanced with those of other creatures. While visitors enjoy lounging in the grass, birds, spiders and insects reap the benefits of the surrounding gardens.