Altadena Heritage Tree Page

Welcome to our Tree Page with information on selecting, planting, caring for and maintaining your trees. We also have information on upcoming or recorded events regarding trees.

 Altadena Heritage has been working to maintain our existing tree canopy as well as increase it. While Altadena is not an urban center but rather suburban, it has a very high “Urban Heat Island Index.” This is because prevailing onshore winds carry heat from the LA basin up to the foothills until they are stopped by the San Gabriel Mountains right in Altadena. We published an article on this in our newsletter.  

Planting Trees Really Helps

Planting trees is a very effective way to combat the Urban Heat Island effect, the others being installing cool roofs and cool pavements. Trees cool the air by transpiration and by shading heat absorbing surfaces. Some additional benefits of trees:  they take pollutants and carbon dioxide out of the air, emit oxygen, encourage active transportation (walking, bicycling) by providing shade, stimulate economic activity, and improve health and wellbeing. 


Learn to Select, Plant and Care for Your Trees

We have reached out to tree experts to help us provide a series of workshops and additional information to help residents make the right decisions about choosing, planting and caring for the best trees that suit our climate and contribute most to the cooling and improvement of our environment.  

This effort is supported by a generous grant from Southern California Edison.

2020 Tree Workshops

September 26, 10 am – 12 pm

Right Tree, Right Place – Tree Selection and Siting

Led by tree expert and plant pathologist, Dr. Jerrold Turney

October 24, 10 am – 12 pm  

Pruning and Tree Care

Presented by tree expert
and plant pathologist,
Dr. Jerrold Turney

November 7, 10 am – 12 pm  

A Tree Planting Demonstration

Presented by tree expert and plant pathologist Dr. Jerry Turney

Tree Resources

Altadena Heritage has compiled the following list of online resources to learn more about trees – how to access, select, plant and care for them.

General Information

L.A. County Public Works will plant a tree in your parkway for free if space meets criteria. Call 818-249-3094 to request a parkway tree.

SelecTree, Cal Poly San Luis Obispo – Website
Provides a wealth of information on any particular species of tree.

Tree PeopleWebsite 
Very active in Los Angeles. This is a great website with lots of information about the Urban Forest, trees, gardening, how to get involved, etc. The DIY section is very good.

California ReLeaf – Website 
Provides grants to communities for arbor day events and for large planting projects. They advocate for planting large trees, as those will have a larger impact on climate change and the urban heat island effect. Website has webinars, videos, slide show presentations, newsletter, links to many resources.

California Urban Forests Council –  Website

L.A. and Orange Counties Regional Urban Forests CouncilWebsite 
Presentations of past seminars available here. Publishes a tree guide.

International Society of ArboricultureWebsite 
Lots of advice for the tree owner, including how to buy a high-quality tree. Will help you find certified arborists in our area and check their credentials.

Urban Tree Foundation – Website  
Research-based advice on tree buying, planting, and care for the professional and the homeowner. See especially this guide: PDF

Tree Care for Birds –  Website  
Best management practices to protect birds and other wildlife during and beyond nesting season. Good resources page and some great photos.

Selecting the Right Tree

LADWP Home Tree Guide – Website

Tree People’s LA City Approved Tree List – click on plant lists – Website

Pasadena Cool Trees Guidebook (2018) – PDF

How to Choose the Right Tree for the Right Place – Website

The Large Tree Argument – PDF

Buying High Quality Trees – PDF

Selecting the Best Site

Pasadena Cool Trees Guidebook – PDF

LADWP Home Tree Guide – Website

Tree Planting & Care

CALFIRE Nursery Standards & Specs  – PDF

Planting to Protect Against Wildfire

With wild fires such a current issue for Altadena residents, here are some articles to help you plant and care for a more fire resistant landscape.

  • A Guide to Defensible Space –
    PDF & PDF
  • Very High Fire Severity Zone Map –
  • Ca Buildings in Fire Zones – Website
  • Pasadena Cool Trees Guidebook – PDF

  • LADWP Home Tree Guide – Website

Fire Resistant Landscaping

Fire-safe Plant Lists

  • Diablo Firesfe – Website
  • Fire Safe County- PDF
  • Tuloume Firesafe –  PDF

Trees NOT to Plant in Southern California – and Why

The following list of trees should not be planted in Southern California due to widespread lethal tree diseases that have no effective treatment. The pests/diseases that are of greatest concern are Bacterial Leaf Scorch and Invasive Shot Hole Bore.

Bacterial Leaf Scorch

Bacterial Leaf Scorch has been present in California for more than 100 years. In 1990 Oleanders started dying and were diagnosed as infected with Xylella fastidiosa in 1993. Soon thereafter Liquidambar styraciflua, Plums, Crape Myrtle and Olive were observed dying and diagnosed as infected with Xylella fastidiosa. Xylella fastidiosa is the causal agent of Bacterial Leaf Scorch. These five hosts are now dying throughout Southern California. Any trees planted will likely die in 5-10 years and have no chance of reaching mature size before they die.

Trees NOT to plant due to Bacterial Leaf Scorch

  • Liquidambar
  • Olive
  • Plum (especially Purple Leaf Plum),
  • Crape Myrtle
  • Oleander

Invasive Shot Hole Borer (ISHB)

Invasive Shot Hole Borer (ISHB) was first found at Whittier Narrows in Los Angeles County in 2003 but was not identified until several years later.

From 2003-2010 the beetle was found on a few ornamental trees, then in 2010 it was the presumptive cause of the death of a large number of box elder street trees in Long Beach. In 2012 the beetle was collected from a backyard avocado tree in South Gate, and from several tree species at local botanical gardens. It now appears to be established in Los Angeles, Orange, and Riverside Counties and has also spread to selected areas of San Bernardino, Ventura and Santa Barbara Counties. A single beetle was caught in Santa Cruz County in 2014. 

The host list for ISHB is now over 60 different tree species. Some hosts are preferred hosts and others are less attractive to the beetle. Preferred hosts of ISHB should not be planted as they will likely die in 5-10 years and never reach mature size before dying. I have observed that all species of Acer (Maple) and Platanus racemosa (Western Sycamore) are highly susceptible and are dying throughout Southern California and should not be planted.

Trees NOT to Plants Due to Likely Death From ISHB
    • Acer buergerianum – Trident maple
    • Acer macrophyllum – Big leaf maple
    • Acer negundo – Box elder
    • Parkinsonia aculeata – Palo verde
    • Platanus racemosa – California sycamore
    • Platanus hispanica – London plane
    • Populus fremontii – Fremont cottonwood
    • Populus nigra – Black poplar
    • Populus trichocarpa – Black cottonwood
    • Quercus lobata – Valley oak
    • Quercus robur – English oak
    • Ricinus communis – Castorbean
    • Salix gooddingii – Black willow
    • Salix laevigata – Red willow
    • Salix lasiolepis – Arroyo willow

Jerrold Turney Ph.D.

Consultant in Plant Pathology and Arboriculture
ISA Certified Arborist #WC-2364
Pest Control Adviser License #75603