Can’t See The Tree For The Forest

P90818Big trees get big problems. Part of our job is to tend to these problems before they become dangerous. Many of these problems are somewhat easy to identify. A deteriorating ponderosa pine with browning foliage it difficult to ignore if it is tall enough to be seen above the rest of the forest more than a mile away.

There are a few problems that are not so easy to identify. Some are caused by the weather, without prior warning. Others are hidden in the forests. One might think that those in the forests would not concern us. However, our landscape and facilities are so intricately mixed with the forests.

The shiner in the picture above was where a big broken limb needed to be cut from a big fir tree. It may not look big in the picture, but the limb was probably more than nine inches wide, and long enough to weigh a few hundred pounds. The lower right edge of the shiner is frayed because the limb broke right at the trunk, and was hanging vertically against the trunk.

The yellow arrow in the picture below indicates where the shiner is located. The trunk of the tree is not as tapered as it seems to be in the picture. It only looks like this because it is so tall that the the upper portion is very far from the camera! Although this fir is a wild forest tree, it is only a few feet from the cabin below. The broken limb was dangling directly over the roof!

There was no way to predict that this limb would break. It did not seem to be any more structurally deficient than those that remain. Of course, once broken, it was removed faster than I could get a picture of it.P90818+

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Horridculture – Stumpy

P90814Among pines, firs, redwoods and most excurrent trees (with central leader trunks), stubs or stumps of limbs that were shed are common and more apparent than they are among decurrent trees (which branch into many main limbs). The older lower stubs slowly but eventually decay and fall away as the trunks compartmentalize (heal over) where they were formerly attached.

However, wild trees are rarely completely without such stubs. As the older lower stubs are shed, newer stubs develop higher up. The worst of their stubs get pruned away only when more refined landscapes are developed around such trees, and they get pruned accordingly. If the trees get groomed regularly every few years or so, not many new stubs get a chance to develop.

When pruning out viable limbs, they must be cut cleanly from the trunk or supporting limb, without stubs. Since they do not deteriorate slowly before falling away, the trunk or supporting limb has no time to start the process of compartmentalizing (healing) over where such limbs were attached. Cutting away cleanly eliminates as much obstruction to that process as possible.

Pruning necrotic stubs from trunks of excurrent trees is not quite so important because the trunks have a tendency to start the process of compartmentalization as such stubs are decaying, and can actually constrict and crush stubs if they do not fall away efficiently enough. Nonetheless, necrotic stubs get pruned out when trees are groomed, just because they are unappealing.

So, no matter what, stubs should not be left when pruning. It is not complicated. It is actually easier to control a saw when it is up against a tree trunk or main limb. Yet, many who do not know better, and many who really should, more often than not, leave trees looking like this fir tree.

No Cherry On Top

P90811Weeping flowering cherry is another type of tree that almost never gets appreciated like it should. Like so many Japanese maples, they get planted into situation where so-called ‘gardeners’ shear them into nondescript globs of worthless foliage that only get in the way. Some get shorn so regularly that they are deprived of bloom. Their form and bloom are their two main assets.

The climate here is not easy on them either. Although comfortably mild, the climate is also arid. This aridity enhances the potential for sun scald of exposed bark. Because upper limbs bend over to hang back downward, their bark is more exposed than that of upright flowering cherries. Consequently, upper limbs are often scalded and ruined, disfiguring the remaining canopy.

Pruning can be complicated. Removal of scalded upper growth exposes inner growth that is more sensitive to scald. It is sometimes necessary to leave damaged upper growth until it gets replaced from below by newer growth. Regular pruning to remove as much of the superfluous lower growth as possible should stimulate more vigorous growth among the stems that remain.

This is really the best technique for preventing scald among upper growth. It may sound silly, but pruning from below to concentrate growth into fewer stems that extend from or through the top of the canopy keeps the top of the canopy healthy and resilient to scald. It also elevates the pendulous canopy that needs to be pruned very regularly for vertical clearance anyway.

It is not easy to see in this picture, but this small weeping cherry tree is developing two distinct canopies. The original upper canopy was damaged by scald and is now disfigured. It is mostly to the upper left of center of the picture. A more symmetrical inner canopy that is developing where superfluous inner growth was pruned out last winter is evident below and to the right.

If there were not a walkway so close to the tree, and I were not concerned with maintaining vertical clearance, I could prune the upper canopy back over a few years, and subordinate it to the healthier lower canopy as it grows through it. Instead, I will prune out most of the inner canopy, leaving only a few vigorous stems that can replace what is missing in the upper canopy.

There is no need to be concerned with it now. The lower stems are not too obtrusive yet. They can bloom next spring, and get pruned out next summer before they really do get obtrusive.

Six on Saturday: Do Not Sit On Tree

 

1. Seriously!P90810

2. Allow me to explain. This is one of three small but very gnarly coast live oaks that grew from the roots of a single tree that was cut down or fell several decades ago. Because the trunks of the three trees are so horizontal and sculptural, children climb on them. Sometimes many children sit on the trunk of this particular tree to get their group picture taken. We had been concerned about how this might compromise the stability of the tree for quite a while. Before we constructed suspension devices to prop it and one of the other two trees with, it destabilized and sagged! We pruned much of the canopy away to eliminate some of the weight that exerts so much leverage against the root system, and propped the trunk with a saw horse. We hope that the tree survives the loss of roots that likely broke away in the process, but would not be surprised if it does not. We are not ready to cut it down. It and the two other trees are so well known and popular among guests. The sign is visible to the right. I will explain the colored yarn on the trunk in a moment.P90810+

3. The subject tree is to the lower right in this picture. The two other trees are sprawled to the upper left. The tree that extends farthest to the left will get propped as well. All three have been pruned more aggressively than they should have been to eliminate much of the weight.P90810++

4. The yarn on the trunks is decoration that the camp counselors installed prior to the arrival of the guests. It must have taken a long time to wrap this much yarn around the trunks, and there is a whole lot more in many other trees. I wrote about it earlier in ‘Boom! Zap! Wow! Bam! Zing!‘.P90810+++

5. This is a completely different coast live oak, with a completely different problem. It needed to be pruned for clearance from an adjacent roadway and walkway. The major limb that was here supported less than one tenth of the total canopy, but because it had been cut back repeatedly, it was unusually bulky. Consequently, the shiner that remains is about as wide ad the remaining trunk! That is VERY arboriculturally incorrect. To make matters worse, the cut was not at the correct angle, so eliminated the lower half of the ‘collar’ that is supposed to expand to compartmentalize (heal) the shiner. The problem now is that by the time the shiner heals, the interior of the trunk may be so rotten that the tree may need to be removed anyway. The limb needed to be removed. The only other option was to remove the entire tree.P90810++++

6. Nothing was done to this coast live oak. It grew like this naturally. Although not an exemplary specimen, it certainly is impressive.P90810+++++

This is the link for Six on Saturday, for anyone else who would like to participate:

https://thepropagatorblog.wordpress.com/2017/09/18/six-on-saturday-a-participant-guide/

Suckers For Street Trees

P90804This grand sycamore has likely been here since the third day of Genesis. A few of the top branches got broken off when Noah’s Ark floated over. When I was a little kid, it was on the edge of a vacant field where road debris was dumped, and older kids rode their dirt bikes. Now it is on the western edge of the parking lot of Felton Covered Bridge Park. I write about it sometimes.

California Sycamore‘, ‘Hanging Gardens Of Babylon‘, ‘Nature Is Messy‘ and ‘Tufts‘ are some of the articles that feature this exquisite specimen. The last three of these examples describe some of the difficulties of old age for sycamores. Something that I may not have mentioned in these article though, is that such mature sycamores eventually develop root suckers.

I use the term ‘suckers’ loosely. For those of us who grow grafted trees, ‘suckers’ are stems that develop from below the graft unions of grafted trees, even if above the roots. They are from the understock below, so are genetically different from the scions above. Unusually vigorous stems above graft unions or on ungrafted trees, including the roots, are known as ‘watersprouts’.

For all other intents and purposes, ‘suckers’ really are just vigorous stems that emerge from roots, which is what we have here. Because no one was here to graft this grand sycamore on the third day of Genesis, these ‘suckers’ are genetically identical to the main tree. Unfortunately, their appearance indicates that the tree is finally acknowledging that it is slowly deteriorating.

Many trees do it, especially old riparian trees. When they know that they will not be around much longer, but still have some time to do so, they divert resources into their own replacement. Suckers are expected to mature into new trees after the original is gone. They recycle the mature original root system until they eventually replace it with younger and more vigorous roots.

Arborists may try to interfere with this process by removing suckers and watersprouts, and diverting resources back into older stems. This is actually helpful for trees that are distressed, but not yet decaying. For trees as mature as this sycamore, removal of vigorous suckers and watersprouts is mostly cosmetic, because thickets of such rampant growth becomes unsightly.

As violent as it sounds, it is best to abscise suckers like these when they first appear, and any that appear afterward. That involves literally tearing them from their roots to remove some of the callus growth from which they emerged. Cutting them at the ground not only leaves the callus growth to develop into distended burls, but also stimulates more vigorous sucker growth!

Now that these suckers have been cut down repeatedly over the past several years, simple abscision is no longer possible. Callus grown has expanded and fused into broad subterranean burl growth. Removal of such extensive burl would severely distress and possibly contribute to the destabilization of the already distressed tree. Suckers can now only be cut down to the ground.

Several years ago, when the first of the suckers started to appear, they were much easier to abscise. The process was delayed until winter dormancy. The small defoliated suckers were then abscised along with much of their associated callus. It did not accomplish much for the massive tree, and only delayed the inevitable for a few years, but generated an interesting byproduct.

The bare suckers with their bit of callus were ideal for growing into copies of the same tree. Most were plugged back into the riparian area nearby, but later killed by necessary vegetation management. A few others were canned (potted), and grew into small sycamore trees that were planted, with other sycamores, into broad medians and parkstrips in Mid City Los Angeles.

It is a long story about how those few trees ended up in Los Angeles, and were added to the fifty or so Birthday Trees that we plant annually on January 18. Sadly, their identities were lost in the process. If the other sycamores are genetically identical clones of each other, it may eventually be possible to distinguish genetic variations of those that were once root suckers here.

Horridculture – Microtrees

P90731We arborists happen to like trees. That is why we are arborists. Most of us also understand that trees are not appropriate for every situation, or where they are not appreciated. There is no point in planting a tree where it will just get cut down by someone else who does not like it. We want trees to be happy. We also want those who live with them to be happy with their trees.
Trees are ‘generally’ desirable over parking lots and roadways. They provide shade that cools the pavement during hot summer weather. Arborists naturally prefer trees that get big enough to make substantial shadows. It is also important for such trees to get high enough to be pruned for minimal clearance above the biggest vehicles to use the roadways or paring lots. They should also be pruned above streetlamps and signs.
Clearance of signs is a serious problem in strip malls and commercial districts, where trees are regularly disfigured by those wanting to keep them below their signs rather than above. It takes a few years to prune trees upward, and many merchants do not want to wait that long. There is also a concern that substantial trees will make substantial messes, and damage concrete curbs, gutters and sidewalks.
Microtrees are not always the answer! They are a cop out! For many situations, it is better to contend with the problems of larger trees than to pretend that microtrees are somehow better.
These dinky crape myrtles will never be proportionate to the roadway to the left or the parking lot to the right. They will not get high enough to be pruned for adequate clearance, so will instead be mutilated for confinement. They will likely get shorn into nondescript globs that rarely get a chance to bloom, and that pedestrians will need to duck under.
Crape myrtle is the most common of the microtrees that so commonly end up where other trees would be better. That is why so many arborists sometimes misspell ‘crape myrtle’ without the first ‘e’.

Exfoliating Bark

P90720KBecause redwoods live for centuries, their bark gets very thick. They do not shed their bark as they grow. Old giant redwoods in the Sierra Nevada have bark that is a few feet thick and thousands of years old. Their bark is thicker than the trunks of what most of us consider to be large trees! Even much younger coastal redwoods that have regenerated here since clear cut harvesting about a century ago have bark that is a few inches thick.
They like their bark thick. It is the insulation that protects them from forest fires that incinerate other vegetation. Unlike most species here that are designed to burn and then regenerate more vigorously after fire, redwoods prefer to survive fire by being less combustible. As they mature, and their bark gets thicker, they become more resilient to fire. There are only a few species here that survive fire mostly intact, rather than regenerate after it.
Of course, survival is more complicated than mere thick bark. Redwoods, particularly coastal redwoods, also try to exclude other more combustible species from their forests. Also, they tend to shed lower limbs that would be more combustible during a fire, and prioritize higher and therefore less combustible canopies. Redwoods have developed a rather ingenious (but unfortunately ecologically delicate) systems of survival techniques.
Other trees are not so easy to figure out. Many species of Eucalyptus shed lower growth as if they want to be less combustible. They shed copious amounts of foliage and bark to inhibit undergrowth and other combustible vegetation. However, not only are they innately very combustible, but because they shed so much of their bark, they lack insulation from fire. It is as if they expect to burn back to the ground, and then regenerate after a fire.
Regardless of their logic, exfoliating bark of the larger eucalypti can be annoyingly messy. Exfoliating bark of some of the smaller eucalypti can be rather appealing in home gardens. This tree happens to be the same featured last week in ‘Silver‘.P90720K+

Horridculture – Street Tree Neglect

P90717Many municipalities enforce tree preservation ordinances. Whether we agree with them or not, these ordinances are designed to preserve significant trees that are assets to the community. For the greater good, local governments have made it their business to limit what we can do with our own trees on our own properties. There are many advantages. There are many disadvantages. We arborists see it all.
Street trees, by general definition, are those that are close enough to a curb to shade a roadway and parked cars. In suburban and urban neighborhoods, many street trees are within parkstrips, which are the narrow spaces between curbs and sidewalks.
Neighborhoods of tract homes are typically outfitted with uniform trees of only one or two cultivars, that were all installed at the same time, as the homes were completed. Some neighborhoods of homes that were built individually are also outfitted with conforming street trees that were installed as parcels were subdivided. Most of such trees were installed as contingencies to development of the sites.
Since such trees were required by the associated municipality, they used to be maintained as such, just like any other trees in parks, medians or other public spaces. Municipalities that lacked tree preservation ordinances protected street trees as the public property that they were considered to be. Those who owned homes that were outfitted with such trees were not allowed to cut them down or even prune them without permission.
In some ways that sounds like a pretty good deal. The problem was that for many municipalities, it did not last. As the maintenance of maturing trees continually became more expensive, resources that used to be allocated for the maintenance of street trees were diverted to other projects. Although they do not like to talk about it, many municipalities no longer maintain their street trees, or do so selectively.
The aging trees remain. Many get cut down secretly by property owners who get frustrated by the lack of maintenance. Most are well maintained, but at the expense of those who own the properties where such trees live.
Most of us probably do not mind paying to have our street trees pruned when necessary. However, it is frustrating for those of us who must contend with some of the more problematic trees, and trees that are unusually expensive to maintain. Furthermore, property owners must assume the expense of repairing sidewalks, curbs and driveways that are damaged by roots, as well as damage to anything that limbs fall onto.
Municipalities that once required the installation of street trees, and that should still be encouraging residents to protect and appreciate their urban forests, are no longer able to assume the liability associated with street trees.
These pictures show two large limbs that fell from a big Canary Island pine onto two parked cars in Leimert Park of Los Angeles. A concerned citizen had contacted the Los Angeles Department of Public Works a few times about the tree, because one of the two fallen limbs had broken off quite some time ago, and was entangled with the other limb that broke and fell shortly before these pictures were taken on Sunday morning.P90717+

Cottonwood

90724Several native species and varieties of poplar are known collectively as cottonwood. Not many are actually planted. They just have a sneaky way of appearing in well watered parts of the garden that are as damp as the riparian areas that they naturally inhabit. Only Fremont cottonwood, Populus fremontii, gets planted, rarely, and only in big spaces that can accommodate its grand scale.

Although too big and too thirsty for most refined landscapes, cottonwoods work well for shade or erosion control in big parks. However, they need to be in a lawn or irrigated landscape if they are not close enough to riparian areas to disperse their roots into soil that is somewhat moist through most of the year. Even in riparian situations, young trees need irrigation until their roots disperse.

Cottonwoods grow fast and big, with aggressive and potentially destructive roots. They should not be planted too close to pavement or septic systems. Vigorous trees might sometimes need to be pruned to reduce excessive weight. Big trees might grow to nearly a hundred feet tall, with wide canopies. Bark is handsomely furrowed with age. The deciduous foliage turns yellow in autumn.

Arborists Are Modern Tree Surgeons

90724thumbThe terminology has certainly changed over the years. Not many of us remember what tree surgeons were, or that there were actually a few different kinds of tree surgeons, who performed very distinct tasks. Tree surgeons are now known as ‘arborists’. Much of what they used to do is done by other types of horticultural professionals. The work that arborists still perform is ‘arboriculture’.

Back when orchards were still common in the Santa Clara Valley, Orange County, and many of the areas of California that are now urban, those who pruned deciduous fruit trees while dormant in winter were known as tree surgeons. Of course, they did other work that the trees needed through the rest of the year, and harvested fruit as well. They might be known as orchardists nowadays.

Tree surgeons also assembled new orchards, as well as individual trees in home gardens. It used to be standard procedure to install the understock of fruit trees in the first winter, and let it grow through the following year. A tree surgeon would return while it was dormant the following winter, to graft desired scions onto it. This is now done by nurserymen in nurseries that sell finished trees.

The tree surgeons who we now know as arborists are, of course, still important. The tree surgery that we now know as arboriculture is the sort or work that other horticultural professionals are not qualified or able to perform. It involves the biggest of trees that are out of reach from the ground, or even from ladders. There are still a few different kinds of arborists, but most must climb trees.

Arboriculture is the horticulture of trees. Arborists are therefore horticulturists of trees. Those who are certified with the International Society of Arboriculture, or ISA, have passed an examination of their arboricultural expertise, and maintain their credential by continued involvement with the educational seminars, classes and workshops of the ISA. Arborist can assess the health, stability and structural integrity of trees, and prescribe and supervise necessary corrective arboricultural procedures.