- Recognizing the difference between a Registered Consulting Arborist and a Certified Arborist
- Tree protection in your city (or county)
- Benefits of the urban forest
- Trees and energy conservation
- Dealing with drought stressed trees
- Planting trees
- To prune or not to prune?
- Topping trees
- Hiring someone to prune your trees
- Tree Tales
The Registered Consulting Arborist (RCA) designation is provided by the American Society of Consulting Arborists (ASCA). The requirements for becoming an RCA are much more stringent than those for becoming a Certified Arborist, and include more years of experience, attendance in an intensive training program, and production of professionally reviewed consulting reports. To read more, or to find a Registered Consulting Arborist in your area, visit the American Society of Consulting Arborists website.
A Certified Arborist has fulfilled an examination, and experience and education requirements, set forth by the International Society of Arboriculture (ISA). To read more, or to find a Certified Arborist in your area, visit the International Society of Arboriculture website.
Both have demonstrated knowledge of arboriculture, and both are likely to work with trees. Both are required to continue their education to maintain their certification or registration and, therefore, should understand current arboricultural issues and techniques. Although both titles indicate that the person has education and experience related to trees, neither title can guarantee or ensure quality work.
Each city and county in Southern California deals differently with tree protection issues. While some municipalities have no protection measures, many have a Tree Protection Program, an Oak Tree Ordinance, or similar programs or laws. Ignoring the measures a local government has in place can lead to project delays, fines, or other means of enforcement.
If you are concerned about municipal requirements or restrictions related to trees, contact the city in which the tree is located (or the county, if in an unincorporated area). While the city or county department which administers a tree protection ordinance does vary from place to place, information can usually be obtained by contacting Planning, Public Works or Parks and Recreation. Start with the website or general telephone information line for your local government.
(this information comes from the Center for Urban Forest Research, Pacific Southwest Research Station, USDA Forest Service, Davis, California. Spring 2003)
Research has shown that healthy city trees:
- Create cleaner, healthier and more breathable air.
- Cool parking lots and parked cars.
- Mitigate the impacts of urban heat islands.
- Shade homes and buildings making them cooler and more energy efficient.
- Block winter winds.
- Retain rain on their leaf and branch surfaces, lessening the impact of storm runoff.
- Increase real estate values.
- Provide neighborhoods with a sense of place.
- Attract more shoppers and more money to business districts.
- Attract new business, homeowners and tourism.
- Reduce domestic violence and crime.
- Improve children’s performance in school.
- Shorten hospital stays and reduce need for medication.
- Lessen exposure to damaging solar radiation.
- Provide restorative experiences that ease mental fatigue and stress.
In Southern California, the need to conserve energy is more critical today than ever. With careful planning, trees can be effectively planted to reduce energy needs on both residential and commercial properties.
A tree’s placement and species, in combination with the climate and season, will affect that tree’s contribution to energy conservation. Buildings under shade will absorb and retain less heat, particularly when trees shade a building’s east and west walls from direct summer sun. In winter, unshaded south walls allow more warmth inside a building. While evergreen trees provide the same degree of shade year-round, deciduous trees provide shade in spring and summer but expose portions of a building to the sun’s rays in fall and winter.
Shade is just one way that trees can modify climate. The air around trees stays cooler, because a tree’s natural processes intercept solar energy and convert water from liquid to vapor form. Where high-speed winds force outside air into a building (for instance, through poorly sealed windows), tree canopies serve as windbreaks.
The information provided here draws from the research of Greg McPherson, James Simpson, and others at the U.S. Forest Service (USFS) Pacific Southwest (PSW) Research Station. Follow the work of the USFS PSW Urban Ecosystems and Processes team, including a beta project that quantifies the value of individual trees: Visit iTree Design to see how much energy—and money—your trees could be saving.
Tree Selection– Proper tree selection for our dry climate will exclude many popular trees in southern California.
Trees that are not appropriate in southern California include European birch, coast redwood, southern magnolia, and many others. Among native trees that may require more irrigation than is available in many cases, are alders, sycamores, and willows.
Trees that should better tolerate our “new normal” include many native and Mediterranean trees, such as:
- Native: coast live oak, blue oak, scrub oaks, Catalina ironwood, black oak, native pines, California bay laurel, California buckeye, and many large shrubs/small trees (such as toyon, Catalina cherry, sugar bush, etc.)
- Mediterranean: cork and holly oaks, Grecian laurel, carob, olive, cypress, etc.
- Other tolerant tree groups: pines, araucarias, acacias, silk oak, junipers, bottlebrush, Melaleucas, some eucalypts, etc.
Watering Practices– One of the challenges that occurs when implementing drastic landscape changes to address drought conditions is that existing trees in the landscape that have relied on frequent irrigation may suffer from inadequate water. This can manifest in various ways:
- Tree species that cannot be sustained in our environment (see above) without abundant irrigation water.
- Withdrawal of all or most irrigation from surrounding landscape neglects water requirements of remaining trees.
- Shallow roots as a result of historical excess irrigation, or frequent but shallow irrigation.
- Drought tolerant trees that are not tolerating this “new” level of drought.
- Salt buildup in soils from applied irrigation water.
For additional information on these topics please contact us.
Selecting the right kind of tree requires a little bit of planning and research. The Sunset Western Garden book is one of several resources for understanding the environmental needs of plants, particularly in Southern California.
Some things to consider about the planting location:
- How much sun will the tree receive?
- How much water will the tree receive?
- Are there any obstacles to growth, such as utility lines overhead, or a sidewalk or building nearby?
- Will the tree be planted in a place where falling leaves or fruit on the ground would be a nuisance? (for example, over a driveway or pool)
Some things to consider about the tree you select:
- What is the mature size of the tree?
- What is the natural shape of the tree? (narrow, broad, weeping)
- Does the tree drop fruit or seed pods which could be considered undesirable?
- How much water and sunlight does the tree need, and how much can it tolerate?
For a more detailed overview of tree selection, visit the International Society of Arboriculture website.
Many newly-planted trees are tied to a planting stake. While a stake may provide needed support soon after a tree has been planted, the nursery stake should always be removed, and if the tree is able to stand without it, no re-staking may be required. In any case, all stakes should be removed as soon as the tree is able to stand up without them (usually within one to two years of planting). If a tree at this stage is very top-heavy, it may be desirable to prune the tree until it can support itself without stakes. A tree that is staked for too long will never be strong enough to support itself without the stake, and the stake ties can injure the tree as the tree grows and the ties become tighter.
We are often asked to provide pruning recommendations, and clients are surprised when we tell them their trees do not “need” to be pruned. It is a common misconception that pruning is ”good for the tree”. Actually, rarely does a tree need to be pruned for its own sake: trees manage their canopies on their own and are able to adapt and survive in their natural environment without any human intervention.
Pruning removes a tree’s stored energy and nutrients that are utilized for tree growth, pest defense, and disease resistance. Pruning also reduces a tree’s photosynthetic rate by decreasing the amount of leaves. Lastly, pruning creates wounds that are an easy place for entry by insects and/or diseases. For these reasons, pruning less is better for a tree than pruning it more.
However, there are situations where a tree’s owner may “need” it to be pruned. Such situations typically benefit human safety or enjoyment and may include removing an unsafe limb or generally improving the safety of the tree, view pruning, power line clearance, etc. Sometimes, trees are pruned simply because the owner wants it to be.
Of course, it’s your tree and you may prune it as you like (within legal restrictions). But we warn tree owners not to be misled by eager pruning contractors, neighbors, friends, etc., who tell you that your tree ”needs” to be pruned. As a very general statement, pruning is not good for trees, and a lot of unnecessary pruning happens in southern California.
Topping (reducing the height of a tree by indiscriminately cutting main branches back to stubs) is a common practice in Southern California, but is considered unacceptable by arboricultural professionals. Just one instance of topping can destroy a tree’s natural branching structure, leaving the tree ugly, potentially unsafe and in need of repeated maintenance.
When a tree is topped, it responds by producing vigorous (but weakly attached) shoots where the improper pruning cuts have been made. The wood where the cuts were made is very likely to decay, further weakening the attachment of these new shoots, and creating potentially unsafe conditions as the tree grows larger. These shoots grow more quickly than those on a properly-pruned tree, and will need to be pruned more often.
There are other methods to reduce the size of a tree, which will be more effective and safer (and quite possibly less expensive) in the long term. For a more detailed overview of topping, visit the International Society of Arboriculture website and look at their handout on “Why Topping Hurts Trees“.
Knowing you have hired the right person to prune your trees can be difficult, but a good rule of thumb is to always hire a Certified Arborist. To search for a Certified Arborist in your area, visit the International Society of Arboriculture website.
Clients sometimes ask us to recommend a pruning company. Although we are in no way affiliated with any pruning company and assume no responsibility for the quality of anyone’s work, we do provide a list of pruning companies which we believe are competent. To request our pruning referrals list, please contact us using the online form.
Please note: We are not affiliated with any organization listed in this website. We do, however, share a common professional interest in educating the general public about trees.
For further useful information, visit Jan’s editorial blog Tree Tales.