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Spontaneous Limb Failure Among Trees

Willows commonly exhibit spontaneous limb failure.

Soil saturation is detrimental to trees for a few reasons. Excessive irrigation is almost as problematic, even without saturation. Chronic excessive moisture compromises stability by inhibiting deep root dispersion. Instead, it promotes shallower root buttressing. It may compromise structural integrity, too. It is generally the cause of spontaneous limb failure.

Spontaneous limb failure is exactly what it implies. Its spontaneity is what makes it more hazardous than limb failure caused by wind. It happens while the weather is calm, warm and perhaps humid, when least expected. Limbs might sag and produce cracking noises immediately prior to falling. However, they quite often fall suddenly and without warning.

Spontaneous limb failure is associated more with gravity than wind. It occurs as vigorous stems literally grow faster than they can support. Warm weather accelerates foliar growth that increases weight. A lack of wind and perhaps enhanced humidity inhibit evaporation from foliar surfaces. Inhibition of evapotranspiration limits weight loss during weight gain.

Deciduous trees are generally more susceptible to spontaneous limb failure. Sweetgum, willows, poplars and elms are particularly vulnerable. A few evergreen trees are likewise susceptible, though. They include coast live oak, Monterey cypress and a few eucalypti. Fruit trees exhibit spontaneous limb failure if they can not support the weight of their fruit.

The potential for spontaneous limb failure is rarely obvious. Limbs of some types of trees may visually appear to be too heavy or floppy. Limbs of Monterey pine, for example, may lean to one side if they sag prior to failure. However, valley oak, carob and sycamore are notorious for concealing their weaknesses. Even arborists can not predict all limb failure.

Wild trees within new landscapes are particularly vulnerable to spontaneous limb failure. They are not accustomed to irrigation through otherwise arid summers. Some can adapt as landscapes with irrigation develop around them. Others overindulge and become too heavy for their own trunks or limbs to support. New trees adapt to irrigation as they grow.

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Soil Saturation Can Drown Roots

Only riparian species tolerate sustained saturation.

Irrigation must adapt to weather. It was unnecessary for exposed vegetation during rainy winter weather. It became necessary through drier spring weather. Now, it must adjust for increasingly warm and dry summer weather. This is not as simple as application of more water more frequently. Excessive irrigation causes soil saturation, which damages roots.

Soil saturation is unfortunately common within landscapes that gardeners maintain. The risk of desiccation is more of a concern to gardeners than wasteful irrigation. Desiccation is certainly more apparent than symptoms of saturation. Besides, gardeners assume the costs of neither water nor damaged vegetation. Chronic damage can become significant.

Soil saturation is less common within gardens that lack gardeners, but is not impossible. Soil within pots can become saturated if vigorous roots clog drainage holes. Water which lingers too long in saucers under pots maintains saturation. Irrigation that is too frequent, too generous or both maintains saturation. Of course, different soil types drain differently.

Soil saturation deprives roots of the aeration that they need to survive. A few species are somewhat tolerant of saturation, but fewer tolerate it for long. With few exceptions, newer roots avoid saturation, so disperse shallowly. For trees, this limits stability and increases their likelihood of displacing pavement. Even shrubbery might develop buttressing roots.

Roots that dispersed prior to saturation are vulnerable to rot as soil saturation increases. This not only destabilizes trees, but also compromises their health. Formerly healthy turf grass and ground cover become chlorotic. Some turf grass becomes infested with fungal pathogens, and perhaps moss. Flowers and fruits might shrivel before they develop fully.

It is impossible to prescribe ideal irrigation schedules and application rates for every site. Climate, soil type, slope, exposure and vegetation types are all considerations. Moisture requirements change seasonally and as vegetation matures. Only direct observation can help determine appropriate irrigation frequencies and rates. It is a very involved process.

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Soil Saturation Kills

Use irrigation responsibly.

London plane tree is trendy not because it is all that excellent, but because it is so reliable. It is actually a rather trashy and messy tree that is susceptible to anthracnose and powdery mildew. Landscapers and gardeners like it so much only because the various maples, oaks and other better trees are more sensitive to soil saturation while they get established.

The truth is that most landscapers and gardeners do not want to put any effort into proper watering. While many of us let our lawns die to conserve a bit of water, they waste enough water on lawns and landscapes to sustain rice paddies! This keeps lawns and landscapes superficially green, but eventually causes problems.

Powdery mildew, anthracnose, molds, blights, rots and all sorts of diseases proliferate in damp conditions. Of course, gardeners are happy to apply fungicides and other chemicals to help control diseases; for a price. Also for a price, they are there to replace plants that succumb to any of the many diseases associated with excessive moisture.

Like London plane, several other trees and plants can survive excessive moisture, but only by adapting. If lower soil is regularly saturated, roots are confined to upper soil. This is not a problem for lily-of-the-Nile and many other perennials that can sneak their roots unnoticed into to the upper few inches of soil. However, trees can not get away with this habit for long; since their shallow and buttressing roots eventually expand to displace pavement, other plants and anything else that gets in their way.

Mature and old trees do not adapt. Their deep roots are already set in their ways, so will only rot if they get significantly more water than they are accustomed to. Oaks are particularly susceptible.

Unfortunately, there is no exact formula for determining how much water lawns and gardens should get. There are simply too many variables, such as soil type, drainage, exposure, weather and demand for moisture. Lawns need frequent watering without much volume. Trees prefer more generous watering, but less frequently.

Lawns and trees and everything else in between all need air within the root zone. Watering should therefore not keep soil constantly saturated, but instead allow for adequate drainage and aeration of the soil between watering, without complete desiccation. New plants will of course need more attention until they disperse their roots, but will be happier and healthier with proper watering.

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Watering Increases As Rain Decreases

Automated irrigation should help conserve water.

Rain is less abundant and less frequent now that winter has become spring. Humidity is decreasing. Temperatures are increasing. Moisture within both the soil and the air is less abundant than it had been. Irrigation that discontinued as the rainy season began should resume soon. Only supplemental watering compensates for the increasing lack of water.

Warmer and drier weather does more than simply deprive vegetation of natural moisture. It also accelerates new growth of formerly dormant or partially dormant vegetation. Such growth requires more moisture as it becomes less available. Increasing day lengths with intensifying sunlight enhance this need for watering. Although natural, it all seems ironic.

This recent need for watering is progressive. Rain still sometimes interrupts it, but will be less frequent as spring progresses. Rain will be very unlikely after later spring. Humidity will continue to decrease as temperatures continue to increase. Watering frequency and volume must increase accordingly. They might not begin to decrease until after summer.

Soil composition and texture also influence the increasing need for watering. Organically rich soils retain moisture more efficiently than sandy soils, for example. Gravely soils that drain well may necessitate frequent watering, even if less copious. Potted plants require frequent watering because they can not disperse roots. Hanging pots require even more.

Furthermore, different types of vegetation need different or specialized types of watering. Fibrous but shallow roots usually need frequent watering, even if they do not need much. Species with deep roots usually need watering less frequently. Some of them need more significant volumes of water than others. Some vegetation prefers only minimal watering.

With all these many variables, there are no simple formulas to determine watering rates. Manual irrigation is easiest to monitor, but is also tedious. Automated irrigation, although less tedious, requires more diligent monitoring. For any particular type of vegetation, soil should not remain too dry for too long. Also, vegetation should not exhibit any symptoms from desiccation.

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Fe

ICK!

Ferrum, which is abbreviated as “Fe”, is the chemical and element name of iron. It is apparently too abundant in this well water. Actually though, it is from the lining of the well. It accumulated because the pump has been inactive for so long. I am impressed that it functions at all after being idle for so long. I am concerned about the lining of the well, though. The hydrologic engineer tells me that I must superchlorinate the well to kill most of the iron oxidizing bacteria, and then flush the well by operating the pump for a long time. That all sounds like quite a bit of risky work. I do not like the concept of pouring something into a well that does not belong there. I am also concerned about what to do with the chlorinated water as it gets pumped out. I suppose that I could apply it to undesirable vegetation around the well. There will undoubtedly be a large volume of such water; but there is also a large amount of undesirable vegetation. I suppose that I could collect some or much of the water into an otherwise unusable tank to let the chlorine slowly volatilize from it. For now, until this superchlorination process begins, I suspect that this water is safe for irrigation. I do not mind if it leaves a temporary rusty residue that eventually rinses away. The water was even muckier before, and will get less mucky as more of it is used, so it could appear to be clean before superchlorination. Besides, I suspect that mucky water is less toxic to vegetation than superchlorinated water is. Because the rain stopped as suddenly as the rainy season began, and no rain is forecast for the next week, irrigation is now becoming a priority.

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Horridculture – Saturation

Saturation is almost a universal problem within almost all of the landscapes that I inspect that are ‘maintained’ by mow, blow and go ‘gardeners’. Without exception, all of such landscapes are outfitted with automated irrigation systems. Some of such systems are scheduled to apply much more water than they should for more time than they should. More typically, irrigation is applied much too frequently. Sometimes, irrigation is both too abundant and too frequent. Such excessive irrigation maintains unhealthy saturation within the soil. Roots are unable to disperse their roots into such saturated soil, and many roots that try ultimately rot. Some trees try to compensate by dispersing roots close to the surface of the soil, but because they are unable to disperse their roots deeply, they lack stability. Also, their shallow roots damage pavement and compete with other vegetation. What is even more egregious about saturation within ‘maintained’ landscapes is that, almost without exceptions, the so-called ‘landscape’ companies that ‘maintain’ them, likely after installing them, brag about their ‘water-wise’ and ‘sustainable’ landscape maintenance techniques. They install irrigation systems that could be quite efficient if they were to operate properly, but then never operate them properly. They install drought tolerant species that can survive with minimal irrigation, but then kill them with excessive irrigation. They replace the deceased plant material, only to kill and replace it again. They do not mind wasting water that their clients pay for, any more than they mind wasting plant material that their clients pay for. In fact, replacement of plant material is profitable for them, since they get paid for procedures associated with removal and installation. Realistically though, they are probably as oblivious to the profitability of their technique as they are to proper technique. In other words, they simply do not care.

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Automated Irrigation Should Adjust To The Weather.

Some irrigation becomes temporarily obsolete through the rainy season.

Now that it has started to rain, what should be done with automatic watering systems? In almost all situations, automatic irrigation systems should be adjusted to accommodate for moisture provided by rain. If rain is sufficient to provide enough or too much water, irrigation can be discontinued until needed again when the rain stops a few months from now.

If the first few storms are discontinuous enough with warm and dry weather mixed in between, lawns and plants that want more substantial watering may need to be watered a few times until the rain becomes more reliable. However, because of cooler temperatures and shorter days, plants do not use nearly as much water as they did during the summer anyway, so do not need to be watered nearly as much as they were only a month or so ago.

Deciduous plants that are losing their leaves need the least moisture, since they can not lose any moisture through evapotranspiration (evaporation from foliar surfaces). The very few plants that bloom or even start to grow during winter use a little bit more water than those that really are dormant, but are still likely get all they need from rain even without getting watered.

Flowering annuals, particularly left over warm season annuals that continue blooming late, may get moldy with too much rain. Their flowers and some of their foliage can turn to mush until there is a break in the rain. Removal of damaged flowers and leaves slows the spread of the mold but does not cure it. Good air circulation among well spaced plants and in exposed areas helps inhibit mold. Regardless, moisture from abundant rain can eventually cause mold to be a problem.

In fact, the only plants that are not likely to get all the water that they need from rain are those that are in pots and planters under eaves or in the home as houseplants. Nonetheless, sheltered plants that are outside should still get much less water now than they do during the long and warm days of summer. These plants are either dormant or at least more sedate because of the shorter cooler days through winter. Houseplants may likewise use less water because the home environment is also cooler.

However, if the heating system of the home decreases humidity, some large houseplants may actually want a bit more water through winter! Humidity fluctuates most in older deficiently insulated homes that are heated by wood stoves or fireplaces; since these homes get humid without a fire burning, but then get much drier with a fire. 

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Aridity Is Opposite Of Humidity

The sky is bluer with aridity.

Aridity is a measure of humidity. Humidity is a measure of aridity. Although opposite, they are similar. Humidity is the quantity of water vapor that is suspended within the air. Aridity is a deficiency of humidity. They are components of weather that are more likely felt than seen. Although, aridity clarifies the air, which typically causes the sky to seem more blue.

Of all components of weather, only atmospheric pressure is less tangible than aridity. It is measurable with instrumentation, but perceptible to very few. Except for its clarification of the sky, aridity is just as invisible. It is more perceptible, though. Just as humidity inhibits dissipation of heat, aridity promotes it. Therefore, arid heat feels cooler than humid heat.

That is why the West Coast is famous for its delightfully arid weather with sunsets. Even when the weather here is warmer than elsewhere, it may be more comfortable. Although undesirable, smog and smoke from forest fires provide color for clear sunsets. Temperate arid weather is more conducive to gardening. However, some vegetation might disagree.

Fragrant flowers can not disperse their fragrance quite as effectively during arid weather. Nor can aromatic foliage disperse its aroma quite as effectively. A few varieties of colorful foliage and flowers may fade a bit faster with minimal humidity. After all, most vegetation within home gardens is originally from more humid climates. It naturally enjoys humidity.

More importantly, most vegetation needs more water through arid weather. It loses much more moisture from its foliar surfaces at such times. Any breeze, which people might like, exacerbates loss of moisture. Obviously, warmth does also. Automatic irrigation requires appropriate adjustment as weather changes. Manual irrigation may become demanding.

Irrigation is less demanding for species that actually prefer local Mediterranean climates. Many of such species are native. Most are native to other regions with similar climates. A few are native to climates that are more arid, but tolerate a bit of extra moisture. Weather and climate do not adapt to a garden. It is best to cooperate with climate than not.

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Irrigation Resumes With Drier Weather

Spring gets progressively drier and warmer.

Spring, in several regards, is like autumn in reverse, or vice versa. Bloom increases for spring but decreases for autumn. Foliage increases for spring but decreases for autumn. The two seasons are in opposition. In this chaparral climate, the rainy season that began last autumn ends now. Irrigation that became redundant then becomes necessary now.

Diminishing rain is not the only reason that irrigation becomes more important for spring. Spring weather also becomes warmer and more arid, or less humid. Warmth and aridity increase evaporation of moisture that rain deposited not long ago. Increasing day length, intensifying sunlight and warmth accelerate plant growth. Such growth consumes water.

This need for moisture is progressive, though. Vegetation certainly requires more water as the weather becomes warmer and drier. However, it does not yet require as much as it will require later during summer. By then, the weather will be even warmer and drier, and the days will be even longer. Irrigation should increase accordingly in regard to weather.

Unfortunately, there are no simple formulas to determine how much irrigation is needed. Some vegetation with shallow roots may require frequent but moderate irrigation. Some vegetation with deep roots may prefer less frequent but more copious irrigation. Rain is possible at any time. It can briefly interfere with the most efficient of irrigation schedules.

Soil also affects irrigation. Sandy soils drain efficiently, but do not retain much moisture. This may not be a problem for some species that tolerate occasionally dry soil. It may be more of a concern for species that prefer more regularly moist soil, though. Dense soils retain more moisture, but do not drain as efficiently. Soil amendments can improve soils.

Manual irrigation is easier to monitor than automated irrigation, but can be tedious. That is why most irrigation is automated nowadays. Automation is more likely to be excessive than insufficient. Desiccation, wilting and other symptoms of insufficiency of irrigation are obvious. Symptoms of saturation may not become obvious until too late for remediation.

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Horridculture – New Lawn for Old Trees

These mature oaks can not adapt to the irrigation that the new lawn requires.

Californian climates are impressively diverse. However, most climates here are chaparral or desert climates, or similar to such climates. That means that almost all rain occurs during the rainy winter season, and that almost no rain occurs during the dry summer season. Vegetation that is native to California is very familiar with the climates here. Therefore, it does not expect rain during summer. This should be obvious.

Some native species can adapt to irrigation during summer. Some may grow faster than they normally would without irrigation, but compromise their natural life span in the process. This is acceptable within some landscapes. Many riparian species are not bothered by irrigation.

However, some species adapt less efficiently. Some do not adapt at all. Some that can adapt while young can not do so while mature. Oaks are a common example of this.

These coast live oaks with a few blue oaks were installed as shade trees within a formerly minimalistic landscape that did not include turf. They were happy with annual rainfall for half a century or so. Then, this generously irrigated lawn was installed around them. They can not adapt to the frequent irritation that the lawn requires. Their roots are succumbing to decay, so will eventually be unable to sustain their foliar canopies. As they deteriorate, decay may eventually compromise their structural integrity and stability. Dieback is already evident within their upper canopies, with lower watersprouts attempting to compensate.

I suspect that the trees will be removed before they deteriorate enough to become hazardous. I also suspect that new trees will systematically replace them prior to their systematic removal. Their eventual demise is likely an acceptable loss, and perhaps expected. Turf with adapted shade trees is likely more important within this particular situation than preservation of these middle aged oaks.

Dieback is evident within the upper canopy. Watersprouts are evident with the lower canopy.