Planting Trees During A Drought
San Antonio City Forester Michael Nentwich concedes not everyone thought the 2010 massive campaign to plant 9,000 trees in San Antonio parks was a great idea, given the ongoing challenge of South Texas’ earth-baking droughts.
Volunteers plant one of the 9,000 trees that have been added to the San Antonio, Texas, parks since 2010. Photo courtesy of San Antonio Parks and Recreation Department
Two years and a historic, extended drought later, the San Antonio Parks and Recreation Department is happy to report an 83-percent survival rate for trees planted in city-owned parks during the first year of the campaign. The second year proved to be tougher, but the stats are still within the acceptable range.
This success, according to Nentwich, can be attributed to watering strategies that not only nourished the trees, but conserved water.
“We knew we faced challenges with this important effort to increase our tree canopy and that it would take a lot of effort to ensure success,” Nentwich says.
“We also knew that if we waited for an ideal time to plant, it would never come. We were prepared with a watering plan to maximize the survival rate while remaining cognizant of the critical importance of water conservation.”
For those who felt water should not be used on new trees during a drought, Nentwich is quick to point out that the amount of water over a three-year period needed to establish a number-15 size tree—commonly known as a 15-gallon tree—is approximately the same as an average San Antonio household uses in 4.5 to 6 days.
The amount of water used to care for a 15-gallon tree is about 1,500 to 2,000 gallons over a 3-year period. In comparison, the average household uses about 10,000 gallons of water per month or 120,000 gallons per year.
“The benefits of planting trees in terms of reducing storm-water runoff; increasing the recharge of our sole source of drinking water, the Edwards Aquifer; providing clean air and cooler temperatures; and increasing commerce far outweigh the usage needed to water the trees,” Nentwich says.
“Since trees are such a valuable part of our community, it makes sense to replace those we are losing due to drought.”
A Texas Forest Service (TFS) report released in February estimates 5.6-million trees were lost across Texas as a result of the 2011 drought. TFS estimates it will cost $560 million to remove those trees, many of which pose safety issues. The estimated loss of economic and environmental benefits provided by the trees is $280 million per year.
And it’s not just Texas. The National Climatic Data Center reported in July that 55 percent of the continental United States was in moderate to extreme drought.
Tapping Into Water Sources
Those figures make planting and maintaining new trees critical to urban areas, says Nentwich. Under his direction, staff members worked hard to help every new tree survive, while making sure every drop of water used was effective and efficient.
Water conservation efforts played a big role in the tree-planting initiative. Photo courtesy of San Antonio Parks and Recreation Department
New trees were watered with water trucks on a 7-day, 10-day, or 30-day cycle, depending on when they were planted. The trees were fitted with 20-gallon TreeGator slow-release irrigation bags. The bags drain in about 6 to 8 hours.
“Coupling the bags with mulch allowed us to water less frequently and more effectively,” Nentwich explains. “The water penetrates much deeper into the soil, and keeps the root ball moist for a longer period of time. The system is extremely efficient and effective.”
When available, the department also uses recycled water to maintain trees. A new practice over the past year involves reusing city swimming-pool water when the pools are drained at the end of the summer season. Six-thousand trees received 320,000 gallons of pool water the first summer.
Another unusual source of recycling occurs when the local water company has to flush pipes in order to improve water quality in some of its storage tanks. Normally the water would flow into the streets from the fire hydrants. Instead, that water flows into the department’s watering trucks.
The San Antonio Water System (SAWS) has made available 64,000 gallons of water, providing for more than 3,200 trees as of mid-July.
Since completion of the plantings in 2010, a regular watering schedule has been maintained. Trees are watered by hand from watering trucks or from quick couplers available in the parks. Trees are watered weekly for the first month. In months two through four, they are watered every 15 days. For the following two to three years, depending on the weather, they will be watered once a month.
Picking Trees To Plant
The majority of the trees were 15-gallon, or 1 to 1-1/2 inch in caliper. Small, medium, and large species were planted, depending on factors such as park location, soil type, the shade the species can provide, their height, and sometimes their fruit.
Large species include live oak, red oak, burr oak, chinquapin, oak, cedar elm, Mexican sycamore, pecan, walnut, and Mexican white oak, among others.
Medium species include Lacey oak, thornless retama, and anaqua.
Small species include Mexican and Texas redbud, Mexican plum, Mexican-buckeye, crepe myrtle, possumhaw holly, Texas mountain-laurel, and desert willow.
“Picking the right species for this area obviously plays a major role in assuring the success of the trees,” Nentwich says.
“We also wanted to use a variety of species to improve the diversity and beauty of the parks while we work to increase our tree canopy and the environmental benefits the trees provide.”
Collaboration And Cash Flow
The $1.4-million campaign was funded from a tree-mitigation fund and a tree-canopy fund, monies collected from developers who pay fees and possibly fines for violation of the city’s Tree Preservation Ordinance.
The average cost per planted tree was $158, depending on tree species and container size. The trees were purchased through use of an annual contract with an outside vendor.
As an off-shoot of the park planting initiative, the department, in order to beautify the central business district, planted 1,000 trees along major thoroughfares, boulevards, and sidewalks, as well as in open space within the downtown area.
This initiative, which cost $500,000, was funded from the general fund for site preparation and the tree-mitigation fund for purchase and installation of the trees.
In a third effort, the city collaborated with the local electric company, City Public Service Energy (CPS Energy), the TFS, and SAWS, to develop a community-planting rebate program known as Green Shade, funded by the American Recovery & Reinvestment Act.
Both commercial and single-family residential customers of CPS Energy are able to purchase as many as three trees and receive a $50 rebate for each tree.
In a related program, citizens may apply for and receive 25 trees to be planted in their neighborhoods as part of the Tree Planting Challenge. Up to 100 trees are available in each of 10 city-council districts.
Calculating The Benefits
In addition to the lessons learned regarding planting techniques and water conservation, Nentwich says the city has garnered important information on how best to continue to increase the city’s tree canopy.
“Partnering with the community through tree adoptions and tree rebates is less expensive and therefore more cost effective than long-term care and establishment of large amounts of trees,” he explains.
“Community forestry programs also help build public understanding of the importance of trees to the quality of life.”
The overall long-term goal of these efforts is to increase San Antonio’s tree canopy from 38 to 40 percent by 2020, a goal resulting from a survey conducted by the American Forests Association in 2007. The survey recommended that 454,600 trees be planted to offset the effects of urban living.
Because the long-term mortality rate for newly planted urban trees can be as high as 50 percent, Nentwich doubled the number and rounded it up to 1 million.
“We can’t emphasize enough how important trees are to the quality of life in an urban area,” Nentwich says.
“In a South Texas summer, trees can reduce ambient temperatures by 12 degrees. They reduce energy costs, reduce storm-water runoff, fight soil erosion, filter the air, produce oxygen, and reduce pollution.”
And they add beauty to the community, a benefit that cannot be measured.
“We still have a long way to go, but we’re making strides,” Nentwich asserts. “We’re off to a good start, and using the lessons we’ve learned along the way, we will strive to reach our goal.”
Kelly Irvin is the public-relations manager for the San Antonio Parks and Recreation Department in Texas. Reach her at Kelly.Irvin@sanantonio.gov.