Should Homeowners Prune Their Own Trees?

While homeowners and property managers can certainly perform minor pruning tasks, significant pruning jobs should always be left to professionals.

Tree pruning is not only incredibly dangerous, but it requires considerable expertise and skill to ensure the tree has the best chance of recovering and thriving. Because few amateurs are equipped to mitigate the dangers involved or sufficiently educated in tree care to avoid harming the tree, it is generally wisest to have a certified arborist carryout this type of maintenance.

Consider the following guidelines when trying to determine if a given task requires professional assistance:

Can you access the target branches from the ground?

Amateur tree pruners should never leave the ground when working. Climbing a tree requires a variety of tools and equipment that few homeowners have, and it also requires a wealth of knowledge regarding safe tree-climbing practices.

It is also important that you do not use a ladder to access high branches. Ladders and pruning are a dangerous combination, which leads to dozens of serious injuries each year. Contact an arborist any time you must access branches more than about 6 or 7 feet above the ground.

How large are the target branches?

Generally speaking, large branches are more dangerous to remove than small branches, and their removal represents a greater threat to the tree than the removal of small branches. Accordingly, you’ll probably want to contact a certified arborist if you need a branch removed that has a diameter in excess of an inch or two.

Are you trained in the proper operation of a chainsaw?

Chainsaws are incredibly effective and helpful, yet dangerous tools, which cause life-changing accidents each year. And while chainsaws are typically treated as standard household tools, they require far more respect than many people give them. If you plan to use a chainsaw to prune your trees, be sure to enroll in a chainsaw safety course first to avoid potentially deadly accidents.

Is the tree healthy or are you removing the branches in response to stress or disease?

Pruning a diseased tree requires more care and expertise than routine pruning. So, while you may be capable of pruning your fruit trees to improve their form, you should probably contact a tree-care expert if you are trying to remove a diseased, mushroom-ridden or pest-infested branch. Only by doing so can you be reasonably sure you won’t make the problem worse.

Do you have the necessary safety gear?

Minimally, you’ll need a hard hat and safety goggles or glasses to prune a tree. However, you’ll also need steel-toed boots, ear protection, and protective chaps if you will be using a chainsaw. You may also want a pair of thick gloves, to help prevent splinters and cuts.

Do you know the proper cutting techniques to use when pruning?

Improper cutting techniques can create jagged wounds, which will take the tree longer to seal up. In some cases, it can even cause the removed limb to strip bark from the trunk, thereby exposing a large portion of the tree to pests and pathogens.

To avoid creating these types of wounds, arborists typically use the three-cut method to remove large limbs. The three-cut technique requires that the pruner cuts halfway through the target branch from the bottom (about 1 foot away from the trunk or parent branch) first. Then, another cut is made about 6 inches inside the first cut, but this time it is made from the top to the bottom. The first cut severs the fibers from the bottom of the branch, preventing them from stripping the trunk bark, and the second cut releases the limb. The third and final cut is placed about 1 to 2 inches outside the branch collar and serves to remove the remaining stump.


If you need help pruning the trees in your yard, contact your friends at Evergreen Arborist Consultants. One of our trained tree-care experts will visit your property, assess the trees in question and recommend a proper course of action. And, if pruning is the right course of action, we’ll already be on hand to carry out the work.

The Magic of Mycorrhizae

Trees are amazing organisms that provide food, shelter and other resources for a variety of living things, including everything from mistletoe to humans. But while it is important to recognize the contributions trees provide to the rest of the planet, it is equally important to recognize the ways other species actually help trees to survive.

Many times, these relationships are symbiotic, or mutually beneficial. Some such relationships are obvious and visible — squirrels and jays, for example, help spread acorns throughout the landscape as part of their feeding and caching behaviors, which helps the trees colonize new areas and perpetuate the species. However, other symbiotic relationships occur out of plain sight.

Microorganisms in the Soil

Although soil appears to be little more than a mixture of dirt, rocks and bits of dead leaves, it is actually a thriving ecosystem, containing an unthinkable population of microorganisms. Some of these microorganisms are beneficial to trees, while others are harmful. Still others fail to interact with trees in any meaningful way.

One of the most important groups of microorganisms that interact with trees are beneficial fungi that live on and inside their roots. These fungi – called mycorrhizal fungi – play important roles in the biology of the trees. Mycorrhizae are fairly ubiquitous in healthy, undisturbed soils and they naturally colonize the roots growing in the area. However, urban soils, which often suffer from compaction are often deficient in these beneficial fungi, which can cause local trees to struggle.

The Mycorrhizal Connection

Mycorrhizal fungi and tree roots form a very tight-knit partnership. In fact, they are often referred to as a single entity: mycorrhizal roots, thanks to their strong bond and blurry boundaries. There are two basic ways in which the fungi interact with the roots: Many mycorrhizae coat the find absorbing roots of plants and trees, forming a type of living shield around the roots. However, some are actually able to penetrate the roots of trees, colonizing the spaces between the individual cells.

The Effects of Mycorrhizae

Mycorrhizal fungi help support tree health in a number of important ways. Some of the most important include:

  • Mycorrhizae help tree roots to absorb more water from the surrounding soil, via the increased surface area they provide to the roots. This not only makes the trees more efficient, it makes them better prepared to survive droughts and reduces their supplemental irrigation needs.
  • Mycorrhizae also helps to absorb more of the life-sustaining nutrients necessary from the soil. This means that trees with mycorrhizal roots require fewer fertilizers and soil amendments to remain healthy.
  • Mycorrhizae help protect tree roots from pathogens and harmful fungi. This is accomplished by helping to support the tree’s health (which naturally increases its ability to fight off pathogens), partially shielding the roots from contact with the pathogens, and by out-competing many of these harmful microorganisms for the resources they need.
  • Mycorrhizae help plants survive transplanting efforts, as they improve the tree’s ability to absorb water and nutrients from the new soil, which helps them to acclimate to their new location more quickly.


If you believe that your trees may be struggling in the often-sterile soils that characterize urban areas, give your favorite local arborists a call! We’d love to help analyze the soil situation of your property and make suggestions to improve it, so that your trees can reach their full potential.

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

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.


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.

The Native Habitat of Redwood Trees

Coastal redwoods (Sequoia sempervirens) are some of the most iconic trees in the world. They grow taller than any other living trees and more massive than all but a handful of others. They’ve shared our planet for millions of years, and over this time, they’ve played an important role in the ecosystems they’ve played a role in creating.

But these amazing trees are not able to grow just anywhere. In fact, the entire global population of naturally growing redwoods is restricted to a 450-mile-long strip, stretching from southern Oregon to Salmon Creek Canyon, near Monterey.

Redwood Range

In total, redwoods have access to about 1.6 million acres of suitable habitat, although they are not the dominant tree species in much of this area. Redwoods represent more than half of the hardwood present in only about 640,000 of these acres. Redwoods occasionally grow at elevations of up to 3,000 feet, although most are found below 2,500 feet. Above these heights, redwoods fail to reach their characteristic size, and other trees begin replacing them in the landscape.

It actually appears that this range is shifting slightly to the north, probably in response to climate change. Fewer new redwoods are growing in the southern end of the trees’ range, while seedlings are popping up in previously uncolonized portions of the northern end of the range.

Climate and Weather

Redwood forests benefit from one of the most hospitable climates in the world. Mean annual temperatures vary between about 50 and 60 degrees Fahrenheit, and the temperatures rarely drop below 15 degrees Fahrenheit or climb above 100.

The forests literally drip with moisture. Most of the precipitation falls in the form of rain, although fog also contributes a substantial amount of moisture to the region. Like most of the Pacific Coast, the region receives most of its rainfall in the winter, with very little rain falling in the summer.

Redwood History

Redwoods were not always restricted to such a small geographic area. In fact, 100 million years ago, redwoods covered most of the northern hemisphere. However, about 20 million years ago, the climate began shifting, which allowed vast glaciers to extend farther south into North America and Asia than they previously had. Ultimately, this killed off mostthe redwoods alive at the time; only a relative handful were able to persist in small pockets of California and China.

But this range was reduced even further in the 19th and 20th centuries, as aggressive logging practices and habitat alteration removed thousands of redwoods from the gene pool. Currently, the redwood forest covers only about one-twentieth of the land that it did 150 years ago.

The Function of Fog

Redwoods reside near the Pacific Coast, penetrating inland as far as 35 miles in some places (although the forest contracts to about 5 miles wide in many areas). The primary limiting characteristic of this range is fog penetration. Fog is crucial to the health of redwoods. In fact, fog is more important than rainfall level in defining the coastal redwood forest type. While redwoods can be grown in areas without nearly constant fog, such as commercial orchards or residences, they do not do so naturally.

Nevertheless, these are still large trees with significant water needs. Large individuals may pull 500 gallons of water a day from the ground. Accordingly, while their habitat is restricted to only those areas that receive regular fog coverage, they do not grow equally well in all areas within these areas. The largest individuals and densest groves typically occur in riparian areas alongside major streams and in flat, low-lying areas – both of which have ample water stores. However, redwoods cannot grow in saturated soils, and soils carrying about two-thirds of their total water capacity are associated with the most productive portions of the forest.

The abundance of moisture in these forests (which are sometimes classified as super-humid) causes transpiration and evaporation rates to fall. Additionally, soil moisture levels remain higher throughout the year, further reducing the water stress that afflicts the trees growing in nearby but fog-free areas in the region.

The Neighbors of Redwoods

Redwoods are the dominant species in many of the forests they help create, although several other trees grow alongside them. Douglas firs (Pseudotsuga menziesii) are one of the most common species growing among the redwoods, but western hemlocks (Tsuga heterophylla) and Sitka spruce (Picea sitchensis) also occur with some regularity.

A litany of animal species live amid the towering redwoods. Small animals – including rodents, birds, reptiles, amphibians and invertebrates – represent the bulk of the local fauna, as occurs in most natural habitats. Rodents are particularly well-represented in the region, including two very large species: the porcupine and North American beaver. Nearly one-third of the country’s native bird species have been documented to occur in the redwood forest, including representatives of all major lineages, from flycatchers to owls.

However, large animals also live in the land of giant trees too. Black-tailed deer and Roosevelt elk – the largest of the United States’ native elk subspecies – browse vegetation amid redwood groves. Black bear, mountain lions and coyotes hunt through the forests, but their numbers are much lower than those of deer, elk and other herbivores, as is common in all habitats.

Frequent Fires Fuel Adaptation

Redwoods, like most other California natives, have a number of adaptations that allow them to survive the relatively frequent fires that occur in the state. Young trees – those less than about 20 years old – frequently die in these fires, but the stands rapidly regenerate in the form of clones, which sprout from the below-ground root systems. Older trees survive most fires, thanks in part to their 12-inch-thick bark. Most trees simply suffer bark damage, which is easily replaced over time.

Interested in Growing Avocados? Check Your Soil First

In the past few years, an increasing number of homeowners have been bitten by the fruit-tree bug. Instead of roses or marigolds, people are interested in growing their own citrus, pear, apple or avocado trees.

But whether you want to start producing tree fruits with an eye toward profit, or you are simply interested in stocking your kitchen with fresh fruit that you grew yourself, it makes sense to select a species and variety that warrants a high price tag. You’ll either pocket more cash while selling your crops at the local farmer’s market or save more money at the grocery store, but you’ll help your bottom line in either case.

And if you are interested in producing a high-priced tree fruit, it is hard to find a better example than the avocado. Avocados are relatively expensive fruit in the first place, but because of climate change and other socioeconomic factors, it is likely to increase drastically over the next several decades. In fact, future harvests are expected to fall by about 40 percent, which will cause the price of avocados to skyrocket.

But you must be sure that you are equipped to care for avocado trees before you start shopping for your stock. You’ll obviously need access to a reliable (and affordable) water supply and plenty of sun exposure, but one of the most critical aspects of avocado production relates to the soil you have available.

Make sure that you address the following soil characteristics before setting out to install your new trees:

  • Soil Structure: Avocados are shallow-rooted trees, whose roots are incapable of penetrating into compacted soils, so it is always best to break up the soil in the planting hole before introducing the tree. They prefer very coarse, well-drained, loamy soils, and they will struggle to thrive in heavy clay soils. Additionally, it is imperative that avocados not be planted too deeply, as this can stress the root systems and damage the trunk. Avocado trees cannot tolerate soggy soil, particularly while the temperatures are low, so it is better to err on the shallow side when you are planting these trees. Many California-based avocado farmers grow their trees on raised mounds, to help ensure adequate drainage and prevent root rot.


  • pH: Avocados grow best in slightly acidic soils, with a pH of between 5 and 7. Alkaline conditions limit the ability of avocado trees to absorb iron and zinc, which will ultimately lead to their demise. You can use elemental Sulphur to help reduce the pH of the soil when necessary, but you must be sure to plan ahead and address these issues before planting your avocados, as it can take six months or longer to properly adjust the pH.


  • Salt: Avocado trees are very sensitive to salt. Salt spray from the ocean, salt in the local water supply and salt in the soil are all problematic, so it is important to consider the salt content of these things and your geographic location before deciding to grow avocados.


  • Fertilization: Avocado trees respond best to small, frequent applications of fertilizer, rather than infrequent and heavy applications. Nitrogen and potassium (particularly after the trees begin to produce fruit) are the most important nutrients to supply to young avocados, while supplemental phosphorus rarely appears necessary. By the time they are about 10 years old, most avocado trees have produced a thick layer of mulch, comprised of their shed leaves. This usually eliminates the need for supplemental nitrogen.

Tree Growth Explained: The Magic of Meristems

From a macro view, trees appear to grow in many different ways through the course of a season. Their leaves unfurl and enlarge in the spring and their fruit swell in the summer.

But this is not true growth – after all, the tree will shed these structures eventually.

True growth occurs when trees produce new wood. This kind of growth produces tissue that persists from one season to the next.

But even this growth is a very location-specific phenomenon, and it only occurs in a few places throughout the tree.

These places are called meristems.

Apical Meristems

Apical meristems occur at the tips of branches and roots. They are responsible for a tree’s longitudinal growth along its axis, or, put more plainly, they are the place from which branches and roots grow longer. Arborists and botanists consider growth from the apical meristem to be primary growth.

However, apical meristems also produce the cells that will become the plant’s secondary growth center – the lateral meristems.

Lateral Meristems

Lateral meristems are found in the thin ring of tissue around the circumference of a tree’s trunk, branches and roots. These lateral meristem regions (which exist along the entire length of the branch or root in question) are responsible for increases in girth, rather than length.

Lateral meristems occur in two different tissues of each branch. The innermost ring is called the vascular cambium, while the outer meristem layer is called the cork cambium. Each produces new tissues from both the inner and outer surface of the ring.

More specifically, the cork cambium produces cork cells on its outer surface and phelloderm cells on its inner surface. The cork cells will eventually die and become the outer bark, while the phellogen is a parenchyma-rich layer of cells that serves to store starch for future use.

Further inside the tree, the vascular cambium produces phloem tissue on its outer surface and xylem cells (wood) on the inner surface. Phloem tissue transports starches along the length of the branches, while xylem transports water from the roots to the leaves and supplies support and stability to the tree as a whole.

The Arboricultural Implications of Meristems

With the understanding that trees only grow from these regions, it is important to apply this knowledge to the ways in which we prune trees. There are a number of ways to use this knowledge, but the following include some of the most important:

  • Because it removes a large number of a tree’s apical meristems, topping is a destructive practice that should be avoided. Removing a branch’s meristem often results in the branch’s death, and it forces the tree to grow from lateral branches, rather than the branch tip.


  • Tree branches do not move higher off the ground with time. Because trees grow from the tips of their branches, and not from the trunk’s base, limbs do not move higher with time. This means that an obstructing limb will remain in the way unless you remove it. Arborists must perform a procedure called a crown raising to deal with these types of limbs.


  • Narrowly spaced, co-dominant stems force material to grow inside the wood of the junction. When a tree produces a pair of trunks, the expansion in girth causes the tree to produce wood around the bark material, sandwiched between the two. This makes such junctions weak, as the bark does not attach well to the wood inside the junction.


Three Great Tree-Identification Apps for Your Smart Phone

There are few aspects of life that remain untouched by technology.

Even the ways we interact with the natural world have changed thanks to the technology available at our fingertips.

For example, if you wanted to identify a tree20 years ago, you’d have to break out a field guide or a dichotomous key. But in the year 2017, all you need is your phone.

A variety of different tree-identification apps are now available, each of which help users determine the identification of the trees around them. We discuss a few of the most popular products below.

Virginia Tech Tree ID

If you spend any time researching trees on the internet, you’ve no doubt stumbled across Virginia Tech’s incredible dendrology portal, that includes a wealth of photographs and high-quality information. But they’ve also produced a stellar tree-identification app, so you can access this incredible data from your phone, while you are actually looking at the tree you are trying to identify.

One of the primary “selling” features of the app (which is actually available free of charge right here or here for both iPhone and Android, respectively), is its flexibility. The app features a number of filtering options, which allow the user to narrow down the potential species in question to just those within the user’s area. In fact, users can narrow down the search criteria so much that the app effectively becomes, in the designer’s words, the “Woody Plants of Where You Are Standing.”

Another exciting feature offered by the app is the ability to send tree-identification questions to “Dr. Dendro,” who will help you distinguish between closely related taxa.


LeafSnap is an electronic field guide – actually, a collection of online field guides – that help users to learn about trees. The app includes a lot of basic information about trees, including many high-quality photos of various species; but LeafSnap’s claim to fame is undoubtedly the LeafSnap feature. To use the LeafSnap feature, the user takes a photograph of a tree they wish to have identified. The application then uploads the photo to a central database, processes the image with an algorithm, and provides the user with a species identification.

LeafSnap also has several interactive features, and the information you collect is automatically shared with scientists around the world. This provides them with the chance to study an incredibly large dataset, and understand what is happening among wild populations in nearly real-time.

A diverse array of scientists, researchers and developers are responsible for the work behind LeafSnap, including representatives from Columbia University, the University of Maryland and the Smithsonian Institution. LeafSnap is available at no cost (you can download it here), but unfortunately, it only includes trees of the northeastern United States, and it is only available for Apple-based systems.

Botany Buddy

Botany Buddy is an interactive plant information app that offers helpful information to users. Botany Buddy not only helps users to identify unknown plants and trees with its 1,300-species-strong database of both native species and ornamentals, it also suggests suitable plants and trees for various situations that may confront professional landscapers or homeowners.

Unlike some other apps, Botany Buddy does not require users to be connected to the internet to access their personal dataset, which can be an important feature when you’re out on the trail, miles away from civilization. Botany Buddy is free to download, but it is only available for iPhones and other Apple products. You can download Botany Buddy at the iTunes store or here.

Mushrooms: Potential Harbingers of Doom

Many homeowners and property managers are surprised when the arborist or tree-care professional they enlisted to prune a tree, spends the bulk of his time explaining the dangers of a tiny little mushroom, growing out of their 100-foot-tall tree.

Surely such a tiny, insignificant little outgrowth poses no threat to the mighty oak growing above it – or does it?

People tend to view mushrooms as rather benign components of the natural world, whether they are growing in the forest or on the trees beside their homes. But in actuality, mushrooms provide important clues about often-unseen world. And while they don’t always foreshadow future tree problems, their presence should never be ignored.

The Anatomy of a Fungus

Mushrooms are the fruiting bodies of fungi. Functionally similar to seed pods, most mushrooms contain millions of tiny spores inside their gills. When the time is right, the mushroom releases its spores, and they float in the wind, until reaching a suitable growing site. There they will start a new fungal colony and begin the process anew.

But while mushrooms are visually obvious, most of a fungal colony lives out of sight. The exact location in which they grow depends upon the species in question and its preferred food source, but many live in the soil or the wood of trees. Taking the form of numerous threadlike filaments called hyphae, the fungus lives in these places, digesting various tissues with which they are in contact. The hyphae will produce mushrooms that break through the surface of the soil or tree once the environmental conditions are right.

You can see these hyphae for yourself by venturing out to the local forest and scooping back a bit of soil. Often, you will see many white or gray threads heading in many directions – these are fungal hyphae.

Decay, Destruction and the Circle of Life

The feeding activity of some fungal hyphae can break down the cellular structure of a tree’s wood. As this happens, the tree’s structural integrity is compromised, and if allow to progress for a length of time, large branches may drop or the entire trunk may fail.

And this is why your arborist spent more time worrying about the mushroom than he did pruning your tree. Not only does the presence of this mushroom indicate that the tree may require removal, it serves as a warning that the branches and trunk may have already become instable. He may not even be able to climb the tree safely.

But it is important to remember that while fungi may be deadly for your growing trees, these same organisms are necessary for life on earth. Were it not for these wood-eating fungi, the world would be overrun with dead trees, and the nutrients inside the dead wood would be forever removed from the food chain.

Additionally, fungal decay provides opportunities for many animals. For example, red-cockaded woodpeckers of the southeastern United States are unable to penetrate the healthy hardwood of the longleaf pines growing in their native lands. However, the birds easily excavate nests in pines that have advanced heartwood rot (which results from fungal decay), as the rot softens the wood considerably.

Not All Mushrooms Are Alike

It is important to recognize that the world is home to thousandsmillionsof different mushroom-producing fungi, and not all of them are destructive to trees. Some, for example, feed on organic material in the soil more than the roots or the tree’s tissues. Accordingly, mushrooms do not always indicate a problem.

The best strategy for dealing with a mushroom growing from your tree’s trunk or roots is to contact a qualified arborist, who can identify the mushroom (often by sending it to a diagnostic laboratory for analysis) and then recommend a prudent plan of attack. The tree may require removal to ensure continued safety, but the arborist may also be able to simply remove an infested branch; if you are really lucky, he’ll tell you that the mushroom is from a non-pathogenic fungal colony, and you don’t have to worry about it at all.

But in all cases, prompt assessment is crucial so contact your favorite arborist without delay.

Alex Shigo: The Father of Modern Arboriculture

No matter the field, subject or industry in question, it is always important to understand the role important predecessors played in shaping the world modern world.

For example, horn players should learn about Miles Davis; baseball players should learn about Mickey Mantle and Babe Ruth;and artists should learn about Picasso, Da Vinci and Dali.

But if you are an arborist, tree-care professional or simply someone who loves to learn about trees, you should familiarize yourself with the work of Alex ShigoPh. D. – better known as the father of modern arboriculture.

The Early Years

Alex Shigo was born in Duquesne, Pennsylvania in 1930. He was a talented and dedicated musician from an early age, who played clarinet for the official United States Air Force Band as part of his service during the Korean War. After the war was over, he enrolled in Waynesburg College, where he eventually obtained a Bachelor of Science degree in biology. Soon after, he was admitted to West Virginia University, where he obtained both a Master’s and Doctoral Degree in plant pathology.

Career Path

In 1960, Dr. Shigo was hired to perform tree pathology work for the U.S. Forest Service. Dr. Shigo stayed with the forest service for 25 years, before he retired and began working as an author and lecturer, sharing his knowledge of trees with all who cared to listen or read. A prolific writer, Dr. Shigo authored and co-authored 160 different books, academic papers and popular pieces during this time.

Major Contributions to Arboriculture

A pioneering thinker in the world of tree science, Dr. Shigo turned many time-honored tenants of tree care on their head. Dr. Shigo’s contributions to the world of arboriculture could fill volumes, but a few of his most important lessons and breakthroughs include:

  • In the 1950s, Dr. Shigo began using a newly available technology – the one-person chainsaw – to learn more about trees. During this time, Dr. Shigo dissected more than 15,000 trees to better appreciate their biology. Researchers had already been carrying out tree dissections for many decades, but most of these dissections were carried out on in a crosscut-manner. By contrast, Dr. Shigo began dissecting trees along their vertical axis, which revolutionized our understanding to the spread of decay through a tree.


  • Thanks in part to these dissections, Dr. Shigo re-wrote our understanding of tree wounds. Specifically, he argued that trees do not heal – they seal up wounds and grow around them. He coined the term CODIT (Compartmentalization of Decay in Trees) to help explain this process and allow tree-care professionals to benefit from the knowledge.


  • Shigo studied the way trees in the forest shed their branches, and compared this with what he learned from his study of decay. In doing so, he realized that the flush-cutting technique preferred by arborists at the time was not the best way to prune trees. Instead, he championed the importance of leaving the branch collar intact, and invented the tree-cut pruning technique, which prevents stripped bark and damaged branch collars.

Dr.Shigo continued to learn about trees and share his considerable knowledge about them for the rest of his life. He died unexpectedly after suffering a fall on October 6, 2006, at the age of 76.

Try to keep Dr. Shigo’s contributions to arboriculture in mind the next time you find yourself looking at a beautiful urban forest. Thanks to his work, those trees will feature full, vibrant canopies and properly trimmed stubs – and they’ll be healthier and more attractive for it.

Meryta Trees

Native to islands in the South Pacific, most species of the genus Meryta are small, evergreen, dioecious trees. The genus contains 28 different species, but scientists routinely add, synonymize and eliminate the occasional species within the group.

Meryta trees are found on several different islands in the south Pacific, but they are best represented in New Caledonia, where 11 endemic species live. Many native cultures existing alongside Meryta trees consider them to be sacred, and protect particularly noteworthy specimens with fences or other boundaries. Among other uses, the Maori use the bark of some Meryta species to produce a dark, red dye.

Culture and Care

Meryta trees are excellent choices for many Californian properties. They’re distinctive foliage and modest size makes them both attractive and manageable in most yards, and their tolerance of salt spray means they even work well right on the coast. Further, Meryta trees do not produce thorns or prickles, require little in the way of regular maintenance and do not cause significant litter problems.

Rated for USDA Hardiness Zones 10 and 11, Meryta trees prefer full- to partial-sun exposure and well-drained, loamy soil. Although they aren’t exactly drought tolerant, they do not require as much water as is commonly supposed. Most Merytas bloom in the winter, although their flowers are relatively inconspicuous, those of some species produce a pleasant fragrance.

Important Species in the Genus Meryta

Although represented by 28 different species, only three are available on any kind of regular basis.

Broad-Leaved Meryta (Meryta latifolia)

Native to Norfolk Island, Australia, the broad-leaved Meryta is an evergreen tree that reaches heights of between 15 and 20 feet. In keeping with the theme of the genus, the leaves of broad-leaved Merytas are quite large, measuring as much as 2 feet in length and 1 foot in width.

Broad-leaved Merytas are quite rare in the wild, and few locations have many individual specimens. In total, scientists suspect that there are no more than 150 mature specimens living in the wild. Although occasionally available from specialty nurseries and similar sources, broad-leaved Merytas are not cultivated as much as Denham’s Merytas or pukas are.

Denham’s Meryta (Meryta denhamii)

Denham’s Meryta is a New Caledonian endemic, that grows to about 20 feet in height. Although noteworthy for their enormous leaves, which may reach 3 feet in length or more on mature specimens, Denham’s Merytas also bear fragrant flowers. This is somewhat unusual for (apparently) wind-pollinated species, but a pleasant treat for homeowners planting the trees on their property.

Denham’s Merytas are cultivated in parts of Australia and Florida, but given their intolerance to freezing temperatures, they are not cultivated as commonly as pukas (who are slightly more cold tolerant than Denham’s Merytas) are.

Puka (Meryta sinclairii)

Like most members of the genus Meryta, the puka bears very large, thick leaves; however, the puka is noteworthy for having the largest non-divided leaves of any New Zealand tree species. Although the puka grows as a single trunk when young, it typically begins to branch out after producing its first inflorescence. It is often the dominant tree species within its native range.

The puka has been cultivated since at least the end of the 19th century, and it remains a widely propagated tree in the modern world. Because of its tolerance to wind and ability to grow in either sun or partial shade, the puka is a common street tree in its New Zealand homeland; and it is being seen with increasing regularity in warm locations worldwide, such as California and Florida. However, as the puka is susceptible to freezing temperatures (as are most Meryta species), it is not suitable for locations in which the temperatures drop below about 28 degrees Fahrenheit.