Street trees are a significant and highly visible portion of the City’s urban forest – essential to improving the quality of life in our urban environment. It is in our own best interests to protect, plant and care for the trees that line our streets.
This was the message Stephen Duprey of the Urban Forestry Division brought directly to the Hancock Park Garden Club membership at its March monthly meeting.
There are some 700,000 street trees in Los Angeles. With the impact of the drought on their health, the infestation of the deadly shot hole borer and other insects and diseases, as well as the limited staffing and budget constraints of the Urban Forestry Division, the fate of our urban canopy is truly at risk. Duprey encouraged local residents to get involved in caring for our trees, and informing others about saving the communal canopy.
A few key points taken away from Duprey’s talk include:
- The Shot Hole Borer (two types: Polyphagous and Kuroshio) probably originated in SE Asia and were first found in LA County in 2012. The beetles carry a type of fungus that is pathogenic (disease causing) to susceptible trees. They tunnel into trees to lay their eggs and introduce the the fungus, which then causes dieback. The diseases and the tunneling activity disrupt the flow of water and nutrients that the tree needs to survive and also weaken the tree’s trunk and branches.
- Trees most susceptible to the Shot Hole Borer are common trees such as sycamore, cottonwood, willow, avocado, white alder and box alder. Look for entry-holes. wet dark staining or gumming, or white powdery exudate on trees (see photo here). Many photos and descriptions of the beetle attacks can be found at www.pshb.org.
- Researchers are actively looking for solutions to control the beetles and disease but to date there is no known method that offers complete control . Stay tuned to www.pshband.org and www.eskalenlab.ucr.edu for further news and developments.
- Besides disease, the biggest threats to tree are from weed whackers and insufficient deep watering. Below is an example of how you can clear an area around your trees to keep the grass away and prevent weed whackers from hacking at the tree. Fill it with mulch so you can keep spoil moist between waterings
- The City of LA has adopted the Native Tree Protection Ordinance, which protects seven of the most common native trees of our area: Coast Live Oak, Valley Oak, California Black Walnut, California Bay, Western Sycamore, Toyon and Mexicana Elderberry. These trees are to be spared from illegal tree removal.
- Permits from Street Services are required for root trimming, tree planting and tree removal. New street trees should ideally be planted in 4’x6′ or 4’x8′ mulched areas, keeping other vegetation away from the base/trunk of the tree, and providing drip irrigation for deep watering of the tree.
- Use LA’s 3-1-1 service (by phone) or download the 311 app to report concerns about trees that are in the public realm.
- Sidewalks need repairing? The City of LA has a new sidewalk repair program, SAFE SIDEWALKS LA which will invest $1.4 billion over 30 years to make sidewalks accessible to everyone. Get started at www.sidewalks.lacity.org or call 3-1-1.
- While there is no ordinance preventing it, the use of artificial grass is strongly discouraged because it kills the beneficial insects and bacteria the live in soil. It can also get very hot, making it unpleasant to walk on for people and pets. Artificial turf is best used in small areas. If used in the parkway, make sure to cut the turf away from the base of any trees so they can be watered. Even mature trees need water or they will be susceptible to pests and disease and eventually die. The loss of mature trees can dramatically change a neighborhood and potentially reduce property values. It is widely documented that mature trees increase property values in neighborhoods.