Garden the Planet - Water Conservation

Cultural manipulation includes creating microclimates, using mulches, establishing optimal soil composition, using pervious paving material, and practicing regular fertilization and pest control maintenance. One of the key tenets of water-conservation landscaping is working with nature.

Microclimates can be achieved by configuring vegetation, building materials and topography elements to create sub-spaces which protect the setting from adverse climate variables such as sun, rain and wind exposure to create a more favorable setting. In these sub-spaces things occur which otherwise would not be possible. Microclimates offer a nurturing environment for non-native as well as native plants to thrive. They also provide a place where people may recreate or relax that is more moderate than the typical climate for that site in that season. Leverage microclimates by grouping plants with similar environmental requirements.

In the context of water conservation, microclimates can be established by using shade selectively so that it benefits plants at certain times of the day or during certain seasons of the year.^[1] Shade can be created immediately by using existing walls and buildings or by erecting fences, arbors or other structures of 6 feet or more in height. Shade can also be established by using vegetative material such as trees and shrubs, however the desired effect will take a moderate to long period of time to be realized depending upon the growth rate of individual plant material. As an additional benefit to the microclimate, the new plant material can be configured to work with existing or imposed vertical planes to temper or block wind. Finally, strategic siting of ornamental trees, shrubs and ground covers can mitigate soil erosion.

Mulch has numerous advantages for the landscape, notably water conservation. Mulch aids with soil temperature regulation, minimizing environmental extremes. Mulch helps prevent erosion by enabling more even distribution of water to the soil. Finally, certain mulches deliver nutrients to the soil during decomposition. Mulch is composed of varied materials from organic to inorganic. All mulch promotes water conservation by inhibiting the evaporation of moisture from the soil. Organic mulches, especially leaf mold, promote the soil’s ability to retain water. Compost, leaf mold, pine needles, bark chips and straw all have an appropriate place in the garden as organic mulch. Additional decorative organic mulches have limited placement, such as cocoa bean or buckwheat hulls.^[2]

Inorganic mulch may also help soil retain moisture. Products such as recycled rubber mulch, gravel and expanded shale may be more expensive initially however they do not break down and seldom need replacing, unlike organic mulch, so the cost savings over time may be advantageous. Recycled rubber has the added advantage of reducing landfill waste.

Soil Quality

Optimal soil conditions allow landscape plant material its best advantage for plant performance. A rule of thumb for modifying lawn soil conditions recommends soil rejuvenation to a depth of six inches, annual beds to eight to ten inches, and perennial beds and shrub borders to 18 to 24 inches.^[3] Rejuvenation might be necessary every three to five years if routine amendments have been applied. Soil composition largely impacts water retention also; a 100 square foot area of sand can retain 60 gallons of water, while a loamy soil can retain 90 gallons and a clay soil as much as 160 gallons of water.^[4] In the context of landscape maintenance, one inch of water will penetrate sandy soil to 12 inches, loamy soil to 10 inches and clay soil to five inches.^[5] Soil aeration should be routine, but not necessarily every season.

Pervious paving allows rain and irrigation water to flow into the earth underneath it, rather than draining into storm drains, rivers and streams. According to the EPA, stormwater runoff can send as much as 90% of pollutants - such as fertilizers, pesticides, and oil and other hydrocarbon liquids found on the surface of traditional parking lots - directly into our rivers and streams.^[6]

Pervious paving can be achieved by using pervious concrete or asphalt, or using soft-set stone instead of hardscape. In all instances water is delivered to the soil beneath, reducing storm and irrigation water runoff.

Practicing regular fertilization and pest control maintenance will allow plant material the best potential to survive and thrive by eliminating competition and prey from the landscape environment. Weeds fight successfully for sunlight, water and soil nutrients, depriving the desirable plant material from these essential elements. Pests such as insects, parasites and disease weaken desirable plants, reducing their natural ability to survive. Conversely, providing an on-going nutrient regimen for plant material promotes healthy growth and reproduction necessary to resist environmental stresses. Organic and inorganic fertilization practices are routinely incorporated into the water conserving landscape management program.

[1] Taylor's Guides. Water-Saving Gardens. Boston: Houghton Mifflin Company, 1990, p. 25.

[2] Smith, Miranda. Gardener's Problem Solver. New York: The Reader's Digest Association, Inc., 2004, p. 54.

[3] Taylor's Guides. Water-Saving Gardens. Boston: Houghton Mifflin Company, 1990, p. 12.

[4] Ibid, p. 11.

^[5] Ibid.

[6]National Ready Mixed Concrete Association. Fact Sheet. "Pervious Concrete: When It Rains, It Drains." 2005.

Environmental improvement through horticultural practices.

Water Conservation.

CULTURAL MANIPULATION