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The Cost Benefit Analysis of Implementing a Sustainable Native Landscape

By Kristin Hess & Leslie McGuire, regional editor

Idaho fescue and Siskyou blue are seen on the left. Chilean aster, a perennial herb, is on the right. Although the first three years of a native landscape are just as labor intensive while the plants are being established, it will be nearly self-sufficient by year four.

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This study compares the conversion expenses for replacing an actual non-native landscape with a native landscape. Proposed by Middlebrook Gardens, an award winning firm that focuses on sustainable landscape architecture and designs, it also includes a comparison of the maintenance costs of the native landscape over a 20-year period. The proposed site is the front lawn area of the San Jose Mercury business site in San Jose, Ca.

Even including the costs of demolition and implementation, the native landscape is still more cost effective. The San José Mercury News pays $4,500 per month to cover most of the services regularly performed on the entire property. These services include mowing and trimming the lawn and other plants, fertilizing every six weeks, annual herbicide applications and tree trimming (up to 15 feet) every six months.

Valley Oak (Quercus lobata): Often, when water tables are low, bubbler systems may need to be installed to soak the young oaks every month.

Implementation of Native Landscape

To replicate the natural rolling hills of the Santa Clara Valley, the total cost of demolition, grading and mounding is estimated at $32,400. Once the area is prepared, new native plants will be planted. Twenty-two oak trees will be planted on the site and three buckeyes, each costing $40.

The lawn area will be sown with nine pounds of grass and wildflower seed, which average $18 per pound. The cost for all seeds will come to $160. Approximately 700 one-gallon plants, each $15, will be planted on the site at a total cost of $10,500. Three pots will be planted with two plants and two pots will have three plants. The pots will cost $250 each and the plants will total $200.

Sketch of the proposed native landscape design for the San Jose Mercury News front lawn area. Various types of oaks are scattered with understory plants nearby. Chaparral, grasses and some small boulders cover the entire area.

All expenses for the pots will total $950. No chemicals will be used in the implementation of the landscape. Because the water table is high, no additional irrigation systems will need to be installed.

In this case, the irrigation system will remain as is, requiring no additional expenses. Three-inch Pro-chip mulch, made from recycled wooden palates, will be added to the new landscape. This will serve as a pest control and water retainer. One thousand three hundred forty-five cubic yards of mulch at $40 per cubic yard will be required for the lawn area, or $53,800. The total cost of implementing the native landscape is $98,810. In addition, a contingency fee of 15 percent, or $14,821, and a design fee of 10 percent, or $9,881, are added to the total cost of the landscape. The final, all-inclusive cost of implementation is $123,512.

Toyon are drought resistant trees that produce small white flowers during June and July then red berries through the winter. They are susceptible to pear blight.

Water Use and Irrigation System Repairs Comparison

Current non-native landscape water use: Recycled, or grey water, has been used on the landscape since 1999. The lawn is watered every day for 10 minutes and in the dry months (generally from June to October), an additional 10 minute watering period is necessary daily. On average, $2,721 is spent each year to water the front lawn area.

Coast live oak (Quercus agrifolia) with a grassland of Idaho fescue and California fescue covering the ground. This oak has a lifespan of 400 to 600 years. It is susceptible to crown rot and root fungus if planted in poorly drained soil. It is not, however, susceptible to sudden oak death.

Proposed native landscape water use: Because initial water needs are very high in the first three years, the proposed native landscape will require the same amount of water currently being used on the landscape for the first two years, and the watering schedule will remain the same as the current. In the third year, the amount of water used will be reduced by half. The watering schedule will shift to every other day in the winter and only once a day in the summer. The total annual cost for water in the first two years will be $2,721, however, annual cost for the third year will be $1,361.

Once the landscape is established, it will adapt to the local conditions, requiring little human intervention. The annual cost to irrigate the landscape would be $75. These water needs will remain the same throughout the remainder of the life of the landscape.

Current non-native landscape irrigation system repairs: An average of $1,040 is spent annually on irrigation.

Bigberry manzanitas (Archtostaphylos glauca) have a lifespan of 50 years. Pruning is recommended for the chaparral twice a year for the first three years. This process replicates a fire disturbance and will allow for new growth on each plant.

Proposed native landscape irrigation system repairs: Because the native landscape will be watered less frequently after the first three years, fewer repairs due to wear and tear are expected. Since damage is most commonly due to wear and tear, there is expected to be a significant decrease in overall repair costs after the first three years. Since repairs, on average, cost $1,040 per year, these expenses are assumed for only the first three years of the native landscape. Damage is also frequently caused by lawn mowers, but these repairs will not occur once the lawn is removed.

Fertilizers and Chemical Controls Comparison

Current non-native landscape: Because recycled water contains more nutrients than potable water, fewer fertilizers may be needed than in a landscape not using recycled water, as mentioned above. However, 200 pounds are applied every six weeks. Plants and flowers receive a treatment of 15-15-15 and the lawn receives a high-nitrogen fertilizer of 27-4-3.

Toyon (Heteromeles arbutifolia): After the first three years, water requirements will be reduced to only 15 minutes each month in the dry months (generally June to October). Winter and spring months require no water.

The herbicide glyphosate is used on a regular basis to control weeds. Every six weeks, 50 pounds of glyphosate is applied in the landscape. For fruit control, 50 pounds of herbicide CT-125 is applied to the landscape once each year. The flower pots do not receive any chemical treatments.

In addition to the $104 for fertilizers and herbicides included in the monthly maintenance cost, an additional $200 is spent every three years on fungicides.

Fawn lilies and Indian warrior are seen near the rock outcropping: The landscape will create its own balance as it does in nature, and any replacements could cause disruption. Grasses and wildflowers will reseed themselves once the natural lifespan ends.

Proposed native landscape: Chemicals are not used on the proposed native landscape since pests and diseases are extremely rare for plants that have adapted to this area through evolution. The plant becomes more susceptible to disease when weakened by a form of stress. There are two possible factors that could result in disease or illness of the plant–a predator from a nearby non-native plant, or severe environmental conditions, such as prolonged drought. Expenses to be considered in such an event would be those necessary to remove the diseased portion of the plant or the entire plant. It is also possible that by simply adding water and relieving the stress of the plant, its ability to resist pests and diseases will be improved. Due to the expected 20 percent attrition rate, the plant would not need to be replaced if removed. Weeds are kept under control with a thick mulch of three inches and there are no expenses in this category.

Plant Replacement Comparison

Current non-native landscape: Every six months the flowers in each of the flower beds are changed to accommodate the landscape to the seasonal changes of either summer or winter. One hundred twenty flats with 36 jumbo flowers are purchased every six months. Ninety of these are planted in the front lawn area. In July and January an additional four flats of annuals are purchased to refresh the flowers pots. Flowers remaining after refreshing the pots may be used to replace those that have died in other parts of the landscape. The total cost to replace the annuals each year is $6,300.

Plants in the landscape are replaced at the end of their lifespan. Typically, five-gallon plants at $30 each are used for each replacement. Every three years, the eight fortnight lily plants are replaced, a total cost of $240 every three years. The lifespan of the escallonia and Formosa firethorn are long enough to not need replacing within the next 20 years. Heavenly bamboo is expected to be replaced every ten years and Indian hawthorn every 20 years. Each will be replaced only once in the 20-year life of the landscape, an additional $60. Plants may also need to be replaced after being killed by an unexpected disease or pest. The olive and magnolia trees are not expected to need replacing within the next 20 years.

Proposed native landscape: There is an expected 20 percent loss rate after the first year, but as plants fill in the landscape, this loss is barely noticeable and plants rarely need replacing. If a plant was to be replaced, the total additional cost would be approximately $45 per five-gallon plant, as native plants are more costly than traditional plants. It is expected that after the first three years, one plant will need to be replaced every two years, for a total cost of $450 throughout the 20-year landscape life. All 12 potted plants will need to be replaced about once every three years at $40 per plant. This will be an additional $540 every three years.

Trees and grasses will not require replacing. An attrition rate of 20 percent is designed into the plan, with the expectation that not all will survive, due to competition for resources.

Labor Comparison

Current non-native landscape: A crew of two men work every Wednesday for approximately two and a half hours on the lawn area. Seventy percent, or $3,150, of the total $4,500 bill is devoted to the front lawn area and 55 percent of the total bill is for labor. This translates to approximately $1,730 of labor devoted strictly to the front lawn area each month. There are occasional additional charges for services not included in the regular maintenance schedule. Complete tree thinnings are performed by an arborist every three years, totaling $1,200 per visit for the entire site. Approximately one-fourth of the trees on the site are on the lawn area, so one quarter of the bill, or $300, is for this area.

All lawn on the property is aerated every year as well as spread with gypsum for optimum health, costing $500 each year. Fifty pounds of gypsum is applied and $350 is spent annually on this service for only the front lawn area.

Proposed native landscape: Labor will be required once a month for approximately 24 labor hours to hand-weed the grassland meadow areas until they are established, or for the first three years. A supervisor would also be present for four hours of the eight-hour day. Hand-weeding the grasses would cost $1,220 each month, or $14,640 each year.

Once the grasses are established, their cutting would take place every six months for three labor hours. A supervisor would be present for one and a half hours. Grass cutting would cost $218 every six months, or $436 every year. At this time, additional seeds can be sewn as a precautionary measure only, since the grass and wildflowers would most likely reseed on their own. Only one half pound of seeds may be necessary and would cost $18 per pound.

It is likely that within a five-year period, the grasses can get too thick. Every five years, it is expected that eight hours will be devoted to cutting grasses to thin them out. This will be a total annual cost of $580.

Pruning requiring two people and a supervisor would cost $450 per visit, a total of $900 each year. Once the landscape is established, the lifespan of the chaparral plants can be extended three times by coppicing them every four years. The total time necessary to coppice a parcel of this size is estimated at 12 labor hours with three hours of supervisory presence, which would cost $675 every four years.

Middlebrook Gardens suggests trimming the trees every five years once they are planted. This would require 16 labor hours with a supervisor for four hours, a total of $900 every five years. It is anticipated that an especially harsh environmental stressor, such as prolonged drought, severe storm, heat wave, and floods will occur every three years. In such cases, six labor hours may be needed to repair the site.

Interest Rate Comparison

Interest rates of five, 10 and 15 percent were used to discount the annual costs of each landscape. In all rates, the proposed native landscape showed that money would be saved over the 20-year life of the landscape. When using a five percent discount rate over 20 years SJMN will spend $606,164 to continue maintaining the current landscape, while the proposed native landscape would cost $189,581 to maintain over 20 years, including demolition and implementation. At this rate, the economic payoff would occur at the beginning of year four.

When using a 10 percent discount rate, the current landscape would cost $416,918 to maintain, while the native would cost $180,881 over the 20-year period. At this rate the economic payoff would occur in the middle of year four.

Lastly, at a 15 percent discount rate, the current landscape would cost $329,627 and the proposed native would cost $175,001 over 20 years. At a 15 percent discount rate the economic payoff would occur at the end of year four. Even at a conservative 15 percent discount rate, the native landscape is still more cost-effective than the current landscape.

Alrie Middlebrook, firm president, Middlebrook Gardens

Founded in 1976 by Alrie Middlebrook, firm president, Middlebrook Gardens has become the premiere firm specializing in sustainable landscaping for both commercial and non-commercial properties. The environmental benefits are obvious—they eliminate the need pesticides, insecticides and extensive irrigation. Winner of the 2004 Business/Environmental Award in the Open Space and Habitat Preservation/Restoration Category by Acterra, Middlebrook Gardens wants to encourage other landscape architects and designers to practice sustainability.

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December 7, 2019, 3:42 am PDT

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