Four Flood Sensitive Species to Watch After Last Month’s Showers

/in , /by

Given our Southern California service area, we talk a lot about drought-tolerant trees. In the best of years, rainfall is light; in the worst, it is nearly nonexistent. This is obviously an important consideration when selecting or caring for trees.

But, as you’ve undoubtedly noticed, we’ve experienced quite a bit of rain lately. To be frank, we’ve received a bit more rain than we’d have liked. And while the safety and well-being of the people and pets living in the hardest struck areas is obviously the primary concern in the immediate aftermath, there are other, longer-term considerations following significant rain events.

Trees need water to survive, but too much water can be deadly. Floodwaters can change the structural integrity of soils, subjecting the roots to failure; they suffocate the roots, depriving them of life-giving oxygen; and, even after the flood waters have receded, they can encourage the proliferation of fungi and bacteria.

Some trees are more susceptible to these problems than others are – you’d have a hard time drowning a mature bald cypress (Taxodium distichum); they have adapted to living in swamps. But some trees become so stressed by flood conditions that they become vulnerable to fungal disease and insect attacks following even relatively minor floods.

If you have any of the following species growing on your property, pay special attention to their condition and vigor over the coming weeks. Chances are, most healthy trees will benefit from the increased moisture over time, but previously stressed or diseased trees will be among the first to fail. As always, reach out to your favorite local arborists, if you suspect your trees may be in danger.

Coast Live Oaks

One of our region’s most ubiquitous and ecologically important trees, coast live oaks (Quercus agrifolia) are somewhat susceptible to flooding. They primarily suffer from root suffocation following storms, but insect and fungal attack also take their toll on these trees.

Cherry Trees

It’s important to understand that there are a variety of factors involved with the flood tolerance of cherry trees. Some cherry rootstocks are very flood tolerant, while others are highly sensitive to saturated conditions. Just be sure that you keep a good eye on your cherry trees over the next month or so, and solicit professional help at the first sign of trouble – if not sooner.

California Redbuds

The pretty little trees with the lavender/pink/purple blossoms and heart-shaped leaves, redbuds are a great choice for many places. In fact, as California natives, they’re moderately drought tolerant. But also, as California natives, they’re not particularly well-suited for surviving droughts. Keep an eye on your redbuds over the next few weeks as they finish blooming.

Walnuts

Walnut trees (Juglans spp.) of all species, varieties and cultivars are fairly intolerant of extended droughts. Many walnuts forced to endure extended periods with wet feet develop water mold infections (typically caused by species of the genus Phytophthora), which can quickly trigger their demise. Some farmers use flood-based irrigation techniques with walnut trees, but these do not last very long and are done under controlled conditions, in which the water can be drained quickly if need be.

 

***

We don’t share this info to frighten you; most of the local trees will surely survive this unexpected bounty of water. But be sure to keep an eye on your trees over the next several weeks, and pay special attention to the foliage. If you see the leaves start to do anything out of the ordinary (yellow, die, curl, etc.), get help at once.

Trees are no match for mother nature’s wind

/in , , /by


Watch the Video Here:

http://www.foxla.com/news/local-news/232272129-story

POSTED:JAN 27 2017 10:10PM PST

UPDATED:JAN 27 2017 10:10PM PST

(FOX 11) –

Winds were erratic throughout the day. In some places, they were like a breeze. In other areas they were so strong they knocked down trees as if they were toothpicks. In some cases, they dropped on top of homes. In others, they damaged sidewalks as the roots of large trees pulled out of the ground.
.
One big one landed on a freeway! A big eucalyptus landed on the 405 in the Irvine area causing a backup in traffic for awhile.

High winds made the drive on the 215 tension-filled for high profile vehicles drivers. The wind was so strong at one point it pushed an 18-wheeler over like a tinker toy in the Devore area.

Michael Green is an arborist. We looked at video after video of fallen trees and, for the most part, he felt the recent rains and the high winds were a fatal combination for some trees.

Said Green, “The heavy rains do play a role in that”… rain saturates the ground… loosens the soil.. and with winds “trees will topple over.”

So you can imagine how Keith Harvey felt when he saw that happen on top of his house! The one in Rancho Cucamonga. Harvey told us, “I was like, get our grandson. Get him up and get him out of there. When I got here just seeing a big old tree on the house I’m like … okay… wow!”

Michael Green says you may not have a “wow” moment if you maintain large trees around your home. He says, get them inspected from time to time,  “and pruned because…. with pruning the can reduce the weight of a tree if its too large you can do some pruning to mitigate it.”

 

Ocean_Avenue_in_Santa_Monica

Santa Monica’s Urban Forest: A Lesson in Success

/in /by

Santa Monica is often heralded as one of the most tree-friendly cities in the country and that is a hard contention with which to argue.

After all, this is a city with a citizen-run Urban Forest Task Force, a $2 million dollar annual tree budget and one of the most extensive urban forest master plans in the country. With luck, cities throughout the state and country will follow Santa Monica’s lead and adopt more tree-friendly policies.

A History of Tree Hugging

Santa Monica’s commitment to trees and the urban forest is nothing new, and the city has been taking steps to ensure the health of the area’s trees for many years.

Way back in 2001, a study performed by the U.S. Forest Service and scientists from the University of California, Davis, found that the city of Santa Monica benefitted greatly from the urban forest and the money spent to maintain the forest was paying dividends. According to the report, the city’s residents realized benefits exceeding the $1.5 million dollars spent annually on tree care by 50 percent.

By this point in time, Santa Monica could already boast a better citizen to tree ratio than most other Californian cities; the nearly 30,000 trees lining the city’s streets and parks in 2001 meant that the city harbored one tree for every three residents. At the same time, approximately half of the cities in California only possessed one tree for every four residents.

Current Canopy Cover

Approximately 34,000 trees currently clean the air and provide shade for the city (2.7 trees for every citizen). The city cares for all trees growing on public lands and the public right-of-way, while property owners must maintain the trees on their own land. Santa Monica schedules pruning according to several different schedules; some trees are scheduled for annual pruning, while others are only pruned once every two, three or five years, as is appropriate for the species and individual specimen.

A 2010 survey of the city’s street trees, commissioned by the city found that 15 species form the bulk of the urban forest. Some of the most numerous species include Mexican fan palms (Washingtonia robusta), Indian laurel figs (Ficus microcarpa), Canary Island date palms (Phoenix canariensis) and southern magnolias (Magnolia grandiflora). Most of the city’s street tree species hail from different areas of the world; none are native to the Santa Monica area.

Nevertheless, several species native to the greater southern California area grow well in the city, and most stakeholders embrace the use of these species as much as is possible. For example, several coast live oaks (Quercus agrifolia) and California sycamores (Platanus racemosa) grow within city limits, as do a few naturalized species (those that are not historically native to the area, but have become naturalized), such as the Peruvian pepper trees (Schinus molle).

Practical Protection

In December of 2011, the Santa Monica city council adopted an urban forest master plan that sought to protect not only the individual trees, but also the entire urban forest for the next 50 years. The plan outlines the city’s approach to urban forestry, including the criteria for tree selection, tree removal and tree replacement.

One of the most helpful components of the plan provides an appeals process that citizens can use when applications for removal are denied or removals stand at odds with the desires of the local community. This contrasts with many other municipalities throughout the country, which offer little to no recourse for citizens dissatisfied with the city arborist’s decisions.

Recognition

Because of the efforts of the Santa Monica city council, the Urban Forest Task Force and the citizens at large, Santa Monica has been recognized repeatedly as a leader in urban forestry. Perhaps most impressively, the city of Santa Monica has been awarded with “Tree City USA” status for each of the last 34 years.

To obtain such a designation, cities must follow four core standards of sound urban forestry management. These standards include the establishment of a tree board or department, the adoption of a tree ordinance, spending at least $2 per citizen on urban forestry and celebrating Arbor Day.

Amid California drought, fears rise of trees dying, falling

/in , /by

APTOPIX California Drought Trees

TreePeople volunteers water a tree at the Los Angeles Equestrian Center Martinez Arena in Griffith Park, Friday, July 31, 2015, in Los Angeles. As Californians and the communities they live in cut back water usage and let lawns go golden, arborists and state officials are worrying about a potentially dangerous ripple effect. Nearby trees are going neglected and becoming diseased or dying. (AP Photo/Nick Ut)

LOS ANGELES (AP) — As Californians and the communities they live in cut back water use and let lawns turn brown, arborists and state officials are worrying about a potentially dangerous ripple effect: City trees going neglected and becoming diseased or even falling.

With cities ordered to reduce water use by 25 percent during the state’s four-year drought, many residents are turning off sprinklers — not realizing that trees can be permanently damaged by a sudden reduction in the amount of water they receive.

“You don’t want to be cutting back the water to the trees,” said Ruben Green, an arborist with Evergreen Arborist Consultants in Los Angeles. “The tree can’t adjust.”

Across the state, 12 million trees died over the past year due to lack of water, according to the U.S. Forest Service. While the bulk of those deaths occurred outside urban areas, conservationists and officials are now focusing on cities, where mandated water reductions are becoming visible in drying limbs and scorched leaves.

Fears that parched trees could pose a danger were heightened this week when a 75-year-old, 75-foot-tall pine tree fell on a group of kids from a camp at a Southern California children’s museum, leaving a boy and girl hospitalized with serious injuries. An independent arborist and another from the city of Pasadena are conducting an investigation into the cause, which has not been determined to be drought-related.

Green visited the site of Tuesday’s tree collapse and said it appeared unlikely the drought was to blame because the area around the tree looked well irrigated and its root system appeared compromised — a sign of rot, decay or injury, not necessarily the drought.

Still, the collapse highlighted concerns about the health of urban trees. Los Angeles alone has more than 25 square miles of parks and some 327,000 trees.

Green and other arborists said they have seen an increase in the number of diseased trees in the city. As they get less water, they become more prone to illness caused by pests. In addition to bark beetles, Green has seen a newer pest drilling tunnels in the trunks of “dozens and dozens of trees.”

Arborists say the number of falling trees and limbs does not appear to have risen in Los Angeles, but there are concerns that could be next. They also are worried that if a strong El Nino brings a wet California winter, already distressed trees will collapse when a storm hits.

“We’re really right on the brink of starting to face more serious issues,” said Cindy Blain, executive director of California ReLeaf, a nonprofit network of urban and community foresting groups around the state. “This is a critical time.”

A new six-person crew removes potentially hazardous trees from Los Angeles parks. So far this year, it has moved out 550 trees — surpassing the 300 removed in an average year.

“They are starting to fail due to the drought, and we want to make sure these trees don’t potentially pose a hazard to the public,” said Laura Baurenfeind, principal forester with the city parks department.

Turf areas in city parks are being watered three times a week, down from at least five when drought regulations were not in place. To help nearby trees compensate, the city and nonprofits are installing makeshift basins to filter water to trees.

Meanwhile, a public education campaign is underway. California ReLeaf has partnered with Save Our Water, a coalition of the California Department of Water Resources and Association of California Water Agencies, to better inform residents about proper tree care during the drought.

Blain said many of the people she’s spoken with say they have forgotten about their trees or gotten worried and began watering at the tree’s base. Trees should be watered from the edge of their canopy.

If a tree goes too long without enough water, it will become unable to soak up liquid at all.

Like many Californians, Bruce Birkett has reduced lawn watering at his childhood home in Los Angeles in response to the drought. Recently, though, he’s watched in grief as the giant cedar in the front yard became brittle and brown.

“That was hard,” he said, “watching this lovely tree looking poor.”

Lodgepole Pine Forest from Cascade Mountain

Without Sufficient Water, California Trees Face Additional Challenges

/in /by

It is not exactly breaking news that the current drought is responsible for the deaths of a significant number of local trees.

In fact, recent estimates by U.S. Forest Service suggest that the drought has killed off at least 12 million trees from National Forest lands. Before the end of the summer, millions more are expected to perish. And although they are not true trees, Joshua trees (Yucca brevifolia) – perhaps the most iconic denizens of the desert and well suited for amazingly arid conditions – are even starting to die, courtesy of the drought.

If the current drought does not end soon, dead trees may number more than 14 million. However, what often goes underappreciated in times of drought is that many drought-stressed trees succumb to pests and pathogens, which they could normally fight off.

Beetles and Trees

Bark-boring beetles and trees have a long, intertwined history. Several different beetle species afflict as many tree species, but those that attack pine trees are of special consequence at the moment.

Adult female pine beetles seek out weakened pines and attempt to bore through the bark. After penetrating the bark, they make tunnels in the tree’s phloem, and begin depositing eggs. The beetles carry a fungus on their bodies that helps convert the tree’s tissues into digestible form for the hatching larvae. Once mature, the beetles tunnel out from the bark, seek out new trees and repeat the process.

The process can spell doom for the trees. By killing portions of the tree’s phloem, the beetles prevent the tree from transporting sugar to its roots, which ultimately starves portions of the root mass. Once this portion of the root mass dies off, portions of the trees are cut off from water.

While one beetle is unlikely to kill a tree, the insects rarely attack trees singly. Instead, the adults release pheromones upon locating a suitable tree; these pheromones attract other bark beetles in the vicinity, thereby forcing the tree to contend with scads of the beetles at the same time. The mass attack likely helps guarantee that some of the beetles will survive the tree’s defenses, and perpetuate the species.

In most years, trees repel the vast majority of these insects with their sap. As the beetle tunnels through the wood, the tree begins exuding sticky sap from the hole, thereby trapping the insect or pushing it out of the hole completely. However, thanks to the water-stressed state of these drought-stricken trees, they cannot produce adequate sap flows to stop the invaders.

Worse than Normal

Make no mistake – these beetles are a natural component of local ecosystems that have played their part in ecosystem dynamics for millennia. Normally, the beetles only manage to take out the sickest and weakest trees in the grove. In this sense, they are helping to cull unfit trees from the habit.

However, as drought-stressed trees are unable to mount an effective defense, the beetle population is exploding. In some areas, their population has increased in size tenfold. Additional factors are also at play, and they are contributing to the population growth as well.

For example, the lack of hard frosts during recent winters has prevented the bulk of the beetle population from dying off. Our region’s abnormally warm temperatures have also played a role in the problem, as the beetles grow, mature and reproduce more effectively in warmer weather. In fact, some bark beetle species now produce two generations per year, rather than one.

What Is the Solution?

Unfortunately, those working on the problem do not agree on the best path forward. Some believe that the only method to save the forests is by thinning the stands drastically. This would help make it harder for the beetles to move from one tree to the next. However, others believe that this approach will have little effect on the insects, and is likely to remove more trees than the beetles will.

For the time being, the best answer is to study the problem in more detail, and learn about the interactions between beetles and the trees that feed them.

Jersey barriers

Irricades: An Aussie Solution to a Californian Problem

/in /by

As we strive to cope with the current drought – which has now lasted about 4 years – we must be sure that our state’s street trees do not get lost in the shuffle. Not only do street trees improve property values, reduce crime and improve the health of those living near them, they help mitigate some of the effects of the drought.

For example, street trees actually help keep our cities cooler by about 5 to 9 degrees Fahrenheit, which reduces the evaporation rate and allows more water to stay in the soil. They also provide shade, which – when placed over external air conditioning units – improves the efficiency of our climate control systems and reduces our carbon footprint. Street trees also help to break up the heat island effect, which further cools our cities and towns.

So, given that our trees are important, but water-intensive, resources, how do we go about protecting them efficiently?

The Right Way to Water

One way is by providing water slowly, which ensures that the water we do allocate to trees is effectively absorbed by their roots, instead of simply running off the soil and down the watershed. Additionally, we must ensure that we deliver the water effectively and do not waste water by spraying it on the tree’s trunks, canopy and the adjacent sidewalk, as sprinklers often do.  In fact, up to half of the water a sprinkler broadcasts over an area evaporates before a tree’s roots can absorb it.

Slowly watering trees is not only beneficial from a water conservation viewpoint, it is better for the trees themselves.  Lightly watering a tree on a frequent schedule – such as we do when watering our lawns — encourages the development of shallow roots. While this is not a problem for grasses, it is less than ideal for trees. Shallow roots prevent the tree from tapping in to deep water sources, which would help them survive future droughts; but shallow roots also predispose trees to wind throw.

Unfortunately, it is not easy or cheap to water a large number of trees slowly and efficiently.

Or is it?

Enter the Irricade

In 2014, Tree People – an LA-based nonprofit group, dedicated to growing a “green and climate-resilient Los Angeles” — began experimenting with an Australian solution for watering urban trees. They call them irrigation pods or irricades, and they have proven to be surprisingly effective.

Essentially, irricades are hollow traffic barriers (sometimes called Jersey barriers or  K rails), filled with water and fitted with a soaker hose. The irricades are placed in suitable areas near the trees (but far enough away that their weight does not harm the tree’s roots) and the soaker hoses are placed in the appropriate places around the root zone.

As the water (about 160 gallons, depending on the exact model used) slowly drains from the barrier and through the soaker hose, it gets absorbed by the soil, and, ultimately, the tree’s roots. Because they distribute the water via a soaker hose, rather than a sprinkler head, the waste is minimal. Further, because the water slowly trickles into the soil, irricades do not waste water via runoff.

There are four primary reasons irricades are so effective:

  1. They rely on existing, “off the shelf” components that are not cost prohibitive.

  2. They hold a useful quantity of water. Most small street trees require only one irricade, while the largest trees require no more than three.

  3. They require minimal labor to utilize. Aside from setting the irricades in place, they need only be filled and inspected weekly.

  4. You can use recycled or gray water to fill the irricades, which saves even more water.

Tree people and the Los Angeles Department of Parks and Recreation placed an initial batch of irricades in several places in 2014, and other locations have followed in their footsteps, so you may have seen irricades without realizing what you were looking at.

Some have complained that they are an eyesore, but most residents have responded favorably. One things for certain, given their renewed vigor, the trees benefiting from the devices are grateful.

foggy forest

The Coastal Redwood Forest’s Foggy Future

/in /by

Most of California’s trees have evolved to live in our periodically parched state. Some species, such as wax myrtles (Myrica californica), produce glossy leaves which reduce water loses, while others, such as black oaks (Quercus kelloggii), send roots deep into the ground to access water few other plants can.

Yet some other trees have evolved a more unusual method for surviving in the arid west.

Creative Water Collection

The Pacific coast’s most iconic trees, the Coastal redwoods (Sequoia sempervirens), are somewhat drought resistant (at least mature trees – saplings are rather susceptible to drought stress), but large trees require large quantities of water. They do not produce especially waxy leaves or deep taproots, so how do they obtain their water?

They – and several of their ecological neighbors — obtain supplemental water in the form of fog. In fact, redwoods often satisfy up to 30 percent of their water needs annually from fog. Fog is a great source of water for the trees and plants of coastal forests, and, historically, its presence has been relatively consistent.

Further, because fog is typically more common during California’s summers than any other time of the year, the water is available at the time it is needed most. Our summers, as you know, are a touch on the dry side.

Methodology

Much of the fog floating in from the Pacific Ocean condenses on leaves and other surfaces, rolls off onto the ground and soaks into the soil. Unfortunately, much of this water evaporates back into the warm summer air before the trees can absorb it with their roots.

Most trees do not significantly benefit from fog blowing across their boughs. However, having evolved in a place where fog was regular and rain was rare, coastal redwoods have evolved the ability to absorb water directly through their leaves.

By absorbing water in this fashion, the trees can help prevent water stress in their leaves. It also helps keep the surface of the leaf cooler, and reduce the rate of transpiration. But most importantly, this water penetrates photosynthesizing cells, which require water to function.

No Monopoly for the Method

Coastal redwoods are not the only species to exhibit this ability; tanoaks (Notholithocarpus densiflorus) and several other inhabitants of these fog-drenched forests are also capable of foliar absorption. In fact, according to a 2009 study by Emily Limm, Kevin Simonin, and Todd Dawson, sword ferns (Polystichum munitum), madrones (Arbutus menziesii) and Douglas firs (Pseudotsuga menziesii) all absorb more water than redwoods do.

This widespread reliance on fog as a water source helps illustrate its importance to the ecosystem. As we learn more and more about the forest, we may find other ways in which fog helps nourish the habitat.

Is Fog Becoming Rarer?

One unsettling factor in all of this is that some climate models predict that global warming may increase the amount of fog, which would likely be well-received by the species of the forest, while others predict that less fog will coat the coast in our warmer future. If the amount of fog decreases, the redwoods and their fellow flora are sure to suffer.

According to the work of University of Washington researcher Jim Johnstone, the amount of fog blanketing coastal California has decreased by about one-third over the last 100 years or so. If his conclusions are correct, it means that not only have the state’s redwoods been suffering from acute drought stress for about 4 years, they have been slowly suffering for nearly a century.

However, other researchers, analyzing different data sets have found the reverse to be true: More fog is coating the coast than ever before, and it is likely to increase in the future.

As is so often the case, only time and further research will reveal the truth.

wildfire

Drought and Wildfire

/in , /by

The current Californian drought presents more problems than are apparent at first glance.

In addition to causing problems for farmers, trees and lawns, the drought is that it predisposes the state to more frequent and more intense wildfires.

Not All Forest Fires Are Created Equally

It is important to distinguish between the different types and spreading characteristics of wild fires, as each has a different effect on the forests.

Ground fires are usually of low intensity, and although they can deplete the rich leaf litter and nutrients of the floor, they are not as hazardous to mature trees. Ground fires burn fuels found below the surface litter.

By contrast, surface fires use fuels found on the surface of the ground, including leaf litter, pine needles, bark, twigs, and fallen branches. Surface fires are of higher intensity than ground fires are, yet they are not as intense as crown or canopy fires. Crown fires are incredibly intense, but they typically require strong winds and plenty of fuel to perpetuate.

Forest Fires Are Natural

Wildfire is a natural component of many western ecosystems, and most native plants and trees have evolved mechanisms for perpetuating the species despite the challenge. For example, giant sequoias (Sequoiadendron giganteum) and ponderosa pines (Pinus ponderosa) have evolved thick bark to help protect their trunks from the heat of forest fires.

Other trees, such as Jack pines (Pinus banksiana), have evolved cones that only open and release seeds once they are exposed to the high temperatures of a fire. By releasing their seeds at this time, the seeds find a bare forest floor, which they need not share with competitors. Many other trees, such as coast live oaks, depend in part on the caching habits of jays, squirrels and other creatures to ensure some of their acorns survive fires, and can sprout in the aftermath.

Paying for the Past

One factor that contributes to the danger of wildfires is the fire-suppression strategies of the recent past. Operating under a philosophy to suppress all wildfires, large amounts of fuel accumulated in the forests, as routine, low-intensity fires were not allowed to clear out this dead wood. Accordingly, when a fire does occur, this plentiful fuel can cause the fires to grow in intensity. Rather than a low-intensity ground or surface fire, a raging canopy fire develops, which kills a great number of trees – even those that are adapted to fire. Current strategies seek to allow low-intensity fires to burn in a controlled manner, which may help prevent canopy fires.

Special Species

Some trees are especially problematic during droughts. For example, coastal redwoods (Sequoia sempervirens), which typically grow in the fog-drenched coastal regions, often go into decline during droughts, and many die. When they do, they increase the chances of a ground fire – which are normally of low intensity – leaping into the canopy, courtesy of the trees’ dead foliage. Of course, many other species can also help fire to ascend into the canopy, but the size of redwoods increases the potential for problems.

Moving Forward

As reported by Time.com, California state officials have already documented more than 120 wildfires on National Forest land.  To help reduce the chances of severe wildfires in the future, the Forest Service is trying to restore the ecological balance of many areas. This includes, among other measures, removing invasive species and planting natives, many of which have evolved various forms of fire resistance.

Most scientists predict droughts to become more severe, more frequent and longer in duration as the Earth’s climate continues to change. These droughts are sure to cause an increase in the frequency of wildfires, while non-native species and past fire management strategies are likely to exacerbate the fires that do begin.

Therefore, while it makes good sense to do what we can on a local level to address these problems, such as thinning overcrowded forests, taking steps to conserve water and planting native species, it is going to require a global effort to address the problems of climate change, and the sequelae that follow.

Myrica_californica

Drought-Tolerant Trees

/in /by

Drought is common throughout the history of the western United States, and it is only likely to become more common  in future. Accordingly, it is wise for Californians to select and plant drought-tolerant trees whenever possible. While now is not an ideal time to plant new trees, as new plantings require a fair amount of water to become properly established, most of these suggested species represent excellent choices, once the drought concludes.

Get to Know Your Natives

Because California has suffered droughts throughout the millennia, many of the state’s native shrubs and trees have evolved adaptations that enable them to survive long, dry periods.  Most of these are capable of surviving droughts once well established.

  • California redbuds (Cercis occidentalis)

  • California sycamore (Platanus racemosa)

  • Pacific wax myrtle (Myrica californica)

  • California bay laurel (Umbellularia californica)

  • Coast live oak (Quercus agrifolia)

  • Scrub oak (Quercus beberidifolia)

  • Valley oak (Quercus lobata)

  • Desert willow (Chilopsis linearis)

  • Hollyleaf cherry (Prunus ilicifolia)

Excellent Exotics

California is not the only place in the world with drought-tolerant trees, and many exotic species are equally suited for surviving low-water periods. While native trees are generally preferable to exotics, you can select some species that are unlikely to spread invasively or cause ecological problems.

  • Jujube tree (Ziziphus jujuba)

  • Kei apple (Dovyalis caffra)

  • African sumac (Rhus lancea)

  • Pomegranate (Punica granatum)

  • Olive trees (Olea europaea)

  • Japanese persimmon (Diospyros kaki)

  • Persian mulberry (Morus nigra)

  • Carolina laurel cherry (Prunus caroliniana)

  • Australian willow (Geijera parviflora)

  • Mulga (Acacia aneura)

  • Bailey acacia (Acacia baileyana)

  • Japanese Zelkova (Zelkova serrata)

  • Arizona cypress (Cupressus arizonica)

  • Honey locust (Gleditsia triacanthos)

  • Strawberry tree (Arbutus unedo)

  • Afghan pine (Pinus eldarica)

  • Bay laurel (Laurus nobilis)

Proper Establishment

In addition to selecting species suitable for drought-stricken regions, you must plant and establish them properly to give them the best chance for long-term survival. For example, when you water the newly planted trees, be sure to soak the soil deeply and infrequently. In contrast to frequent, shallow watering, deep, infrequent watering causes trees to develop deep root systems. These deep root systems enable trees to draw water from deep within the substrate during parched periods.

Further Reading

For more information on drought-tolerant trees, see these resources: