Citrus College is about to spend $400,000 to plant drought tolerant xeriscape, California oak trees that will utilize synthetic turf and decomposed granite.
However, the technique is highly controversial among plant scientists who say xeriscaping, also known as drought tolerant planting, is environmentally unsustainable.
The method can deplete groundwater, destroy natural soils and contribute to the urban heat island effect, which raises temperatures in cities.
Rather than contributing to the health of our environment, drought tolerant plants condition the soil for desert dehydration. Desert plants can deplete natural aquifers over time. They kill microbiota in the soil, which is the living part of the earth.
On May 3, Cal State Fullerton faculty member, certified arborist and plant physiologist, Sarah Taylor-Laine visited Citrus to assess the health of its trees.
She noted many of the trees on campus are sick or dying. Improper trimming, watering, invasive tree varieties, climbing spikes, lawn mower damage and even fertilizing with decomposed granite stresses the trees to the point of vulnerability.
“Decomposed granite can limit both water percolation to the soil, and gas exchange,” Taylor-Laine said. “Decomposed granite can react with water to form a caustic solution.”
The caustic moisture burns tree roots, killing them slowly over months or years.
“Anytime you get an unhealthy plant, they are more susceptible to disease, fungi and polyphagous borer beetle,” APU and Cal Poly Pomona Professor Ann Croissant said.
Croissant holds degrees in biology, plant physiology and botany.
She founded the Glendora and San Gabriel Mountain Conservancies, which have won several prestigious research grants since being founded in 1991.
She encourages returning the region to its native plant varieties, which replenish natural aquifers and slow forest fire expansion. She also rails against popular drought tolerant planting techniques.
“Groups like the Sierra Club react to climate disaster,” Croissant said. “[The conservancies] try to prevent them. It’s a ‘hands-on’ approach to stewardship.
Citrus College director of facilities and construction Fred Diamond said he had never heard of the Glendora Conservancy.
“We’re spending hundreds of thousands of dollars to landscape,” Diamond said. “We have planted hundreds and hundreds of drought tolerant plants. Some of those are the native grasses.”
Ground supervisor Randy Cable brushed off the possibility of talking with professor Croissant or any other plant scientists, unless he had chosen them as consultants.
Cable didn’t speak for most of the joint interview, but when he did, it was unpleasant.
“Sounds like you’re trying to criticize something you don’t know what you’re talking about. This is what I do for a living–taking care of this campus, not just for water–for usage, for students, for aesthetics, for safety,” Cable said.
Diamond also dismissed the concerns.
He said, “Of course we would use native grasses, blah blah, blah, blah, blah [sic]. A lot of times they die. Over at student services, when a landscape architect put in all of that grass…I forget the name of it. Every bit of it, during the drought…It all died. It was a native plant, a grass.”
Native plants often perish from over watering or other mismanagement. Cable says they can only water on campus three times a week for 30 minutes at a time during the summer.
In addition to campus trees being poorly maintained, some are potentially dangerous. Several trees in the parking lots of our campus are decayed or on the verge of dying. Laine-Taylor who regularly testifies as a tree expert in liability lawsuits noted many potentially hazardous trees.
“This is another tree I wouldn’t hold a tea-party under,” Laine-Taylor repeatedly said to highlight the danger of collapsing limbs on the campus.
Eucalyptus trees particularly concerned her because of the brittle wood of the invasive variety. They are susceptible to limbs falling.
Diamond noted other campuses have them and that falling trees are always a liability. Cable scoffed at liability issues raised by having Eucalyptus on campus.
“There is no law. There is no law,” Cable said.
Relevant case law comes down from the California Supreme Court. In Coates v. Chinn (1958) the court found Eucalyptus presented a danger to passers-by because of trees “natural propensity” to “drop their limbs.” Laine-Taylor said Eucalyptus are inadvisable to plant in areas with high foot-traffic.
When these concerns were raised to Diamond, he repeated his own pet phrase, “Every expert has their opinion.”
Cable joined the refrain, “Everything you do, you’re going to have someone with an opposing opinion.”
When asked if they would reconsider the project, Diamond said “The job’s been put out to bid. It’s pretty much solidified.”