Mulch Retains Moisture And Insulates

Mulch helps to insulate the soil.

Nature is smart. It should be. It has been operating efficiently since the beginning of time. That is certainly longer than anyone has been gardening in defiance of nature. Imported plants that need unnatural watering and soil amendment continue to benefit from nature. Some assets, such as weather, are direct from nature. Some, such as mulch, are copied.

Summers are long, dry and somewhat warm here. Without rain, there is plenty of time for the soil that roots inhabit to become dry. Warmth and aridity increase the consumption of moisture by plant species that are not accustomed to such extensively dry weather. That is precisely why landscapes and home gardens are so reliant on supplemental irrigation.

Because water is expensive, plants that do not require much of it are popular. Automated irrigation systems should operate as efficiently as possible to minimize waste. Since turf grass is very consumptive, lawns should not be overly expansive. Conservation of water is common here. There are several techniques for doing so. Mulch is one of the simplest.

Although adding mulch to a garden is unnatural, it works like the natural detritus within a forest. It retains moisture and insulates the surface of the soil. Without mulch, surface soil can become uncomfortably dry and warm for roots. Mulch also inhibits the proliferation of weeds. Because weeds consume moisture, their absence indirectly conserves moisture.

Mulch generally goes into the garden during early spring, before weed seed germinates, and after the removal of the detritus of winter. It can be practical at any time though, even as the soil becomes dry and dusty through summer. Various forms of mulch are available from garden centers. Home compost works splendidly, but costs nothing more than labor.

Alternatively, several types of groundcover can function as mulch. Some types consume more moisture than they conserve, but exclude weeds. Some types, such as ceanothus, lantana and licorice plant, might not crave any more water than the plants they surround. Their maintenance should involve less effort than removal of weeds which they displace. They are more visually appealing anyway.

Saturation Of Soil Distresses Roots

Some riparian plants tolerate soil saturation.

Saturation of the soil should be a rare problem within the local chaparral climates. Water is a limited resource. That is why plants that are not native or endemic to other chaparral or desert climates rely on supplemental irrigation. Many exotic species would not survive through the locally long and dry summers without it. Water is only sufficient during winter.

The unfortunate reality is that soil saturation is among the more common problems within landscapes that rely on gardeners. Although most gardeners are proficient with irrigation, some are not. They would prefer to irrigate too generously than risk desiccation. They do not assume the expense of the water, or of the plant material that succumbs to saturation.

Although significantly less common within home gardens that do not rely on professional gardeners, soil saturation is possible. It occasionally happens within pots or planters that lack adequate drainage, or if the drainage becomes clogged. Saucers that contain water that would otherwise damage decking or flooring might inhibit drainage if constantly full.

Besides within pots and planters, saturation is more likely within dense garden soil than within coarser soil. Downspouts could saturate surrounding soil through the rainy winter season. Leaky plumbing might do the same at any time, even if it is merely irrigation pipe that leaks only while operating. Of course, excessive irrigation produces most saturation.

Saturaturation deprives soil or medium of aeration. Roots avoid soil or medium that lacks adequate aeration. Trees and large shrubbery therefore disperse most of their roots near the surface of saturated soil. Such shallow root dispersion limits stability. The expansion of such shallow roots displaces and fractures pavement and curbs, and heaves lawn turf.

Excessive irrigation causes soil saturation during summer. Excessive frequency is more likely to cause saturation than excessive volumes of water. Unfortunately, it is impossible to prescribe appropriate irrigation schedules and application rates. Climate, soil type and plant material are all relevant considerations. Moisture requirements change seasonally, and from year to year, as plants mature.

Watering Water Wise Plants

Excessive watering rots drought tolerant yarrow.

Native plants like coast live oak, valley oak, toyon, flannel bush, Western redbud and California lilac (ceanothus) are among the most resilient of plants as the weather gets dry and warm after spring. So are plants from similar climates, like bottlebrush, oleander, rockrose, grevillea, acacia and eucalyptus. They survive dry summers by dispersing their roots deeply into soil that does not get as desiccated as surface soil naturally does (without irrigation).

Ironically, these most resilient plants can also be difficult to work with while they are young. Because they rely on extensive root dispersion for survival, new plants that have not yet dispersed their roots can not survive long without regular watering. They only become tolerant to drought as their roots disperse into deeper soil.

However, because they are adapted to arid conditions, they do not like to be too damp for too long. Roots soon rot in soil that does not drain adequately between watering. They therefore need to be watered frequently, but not too frequently. Yes, that is as confusing as it sounds.

To make it even more confusing, these plants will need less watering as they mature and disperse their roots. Bottlebrush, oleander, contoneaster, hop bush, firethorn, grevillea and juniper can certainly tolerate more water than they really need; but wasting water is contrary to selecting drought tolerant plants to conserve water. Manzanita, coyote brush, rockrose, flannel bush and redbud may actually succumb to rot if watered too much. Even perennials like Pacific coast iris and yarrow can have problems.

Pine, oak, acacia and especially eucalyptus disperse their roots as soon as they can, so do not want to be confined in containers. It is therefore best to plant smaller young specimens than larger ones. #5 (5 gallon) eucalypti get established in the garden more efficiently than larger but more expensive #15 (15 gallon) trees. If #1 trees were available, they would be even better.

Succulents For Better Or Worse

There are all sorts of succulents.

Succulents, both old and new, have been something of a fad for quite a while now. There are certainly many reasons for them to be popular. They add bold form, texture and color to the garden. Most adapt excellently to container gardening. Many types are resistant to pathogens. Succulents are generally easy to maintain and equally as easy to propagate. 

However, one of the primary premises of the increased popularity of succulents is simply untrue. Contrary to popular belief, not all succulents are drought tolerant. Only those that are naturally endemic to desert or chaparral climates can survive with minimal irrigation. They neither expect nor require any more moisture than the rain that falls through winter.

Many succulents are naturally endemic to climates that are not arid. Some are even from tropical rain forests. Such succulents rely on watering to compensate for the local lack of rain through the long and warm summers. Furthermore, many succulents from chaparral and desert climates also want water if their undispersed roots are confined to containers. 

Many popular succulents are cacti. They lack foliage, and are instead armed with spines and thorns. (Spines are modified leaves. Thorns are modified stems.) Their fat succulent stems are green to compensate for their lack of foliage, by conducting all photosynthesis. Generally, most cacti actually are tolerant of drought, although less so within containers.

However, many of the most popular and trendy succulents have succulent leaves as well as succulent stems. Some obscure their stout stems within densely set foliage. Although some are chaparral plants that are somewhat drought tolerant, many require watering for adequate hydration. Even Epiphyllum, which are tropical cacti, require regular watering.

Furthermore, many of the succulents that can survive through dry summers without water take drastic measures to do. Various species of Aeonium and Echeveria let much of their older foliage shrivel to conserve moisture for the younger foliage. Echeveria retain much of their shabby dry foliage as insulation. So many of the succulents that have potential to survive without watering are happier with it.

Roots Prefer To Roam Freely

Some yuccas are unhappy in pots.

Roots are innately mysterious. They consume much of the resources that plants require. They stabilize the stems above them. Few plants can survive without them. Yet, roots are very secretive about their work. Almost all are invisibly subterranean. Consequently, they get minimal consideration. A lack of consideration is a root cause of many root problems. 

Every plant species has distinct environmental preferences. Some plants require full sun exposure. Others tolerate or prefer partial shade. Some are more discerning than others. Similarly, plants that naturally disperse their roots extensively dislike confinement of their root systems. Small plants and some riparian plants are more adaptable to confinement.

Annual bedding plants and many small perennials perform well within pots, planters and small spaces because they do not need to disperse their roots extensively. Some woody plants with fibrous root systems, such as azalea, boxwood and andromeda, can adapt to confinement also. Occasional pruning can keep them proportionate to their root volumes. 

Most of the popular succulents perform remarkably well in confinement. Some types that disperse their roots extensively if necessary will adapt to confinement by dispersing their roots only as far as they must. If they get all they need within a pot, they need not go any farther. However, succulents that are endemic to dry desert regions are not as adaptable. 

Desert plants can survive warm and dry summers because they disperse their roots very extensively. They can not do so within the confinement of pots and planters. This should not be a problem that systematic irrigation can not compensate for. Unfortunately though, these same plants are too susceptible to rot if their roots are damp during warm weather.

So, some plants that are the most resilient in the ground are the least resilient in pots. Of course, this is not an absolute rule. Yuccas from tropical and temperate climates perform well either in the ground or in pots. Those from desert climates are likely to rot in pots. In general, drought tolerance and container gardening are two fads that are not compatible. 

Natives Are Right At Home

Some native plants should stay wild.

Long before people came here and imported exotic (non-native) plants from all over the world, native plants had been perfectly happy without any pruning, watering or fertilizing. They had always been perfectly happy with local soils, local climates and even occasional wildfires. Many are still happier in the wild than in seemingly more comfortable refined gardens and landscapes.

It really makes sense though. Most exotic plants need to be watered because they are from climates that naturally get more rain. Some want to be fertilized because they are from regions with different soil types. Some plants prefer cooler winters. Others want more humidity. They crave what they would get in their respective native homelands.

However, plants that are native to California are not necessarily native to here. California is a big place with all sorts of climates and soils. For example, the desert fan palm that is native to warm and dry Palm Springs would not be happy in cool and foggy San Francisco. Big leaf maple that likes the cool winters of the Siskiyous does not like the mild winters near the coast of Los Angeles. The best natives are those that are native to a particular region, or similar region.

Also, there are a few native plants that are not so easy to accommodate in every home garden. Both the giant sequoia, which is the biggest tree in the world, and the coastal redwood, which is the tallest trees in the world, are native to California. Even if the local climate is a good fit, the space available may not be.

One of the most difficult problems for so many natives though, is that they are sensitive to the regular watering that most exotic plants require. The regular watering that lawn needs just to survive is enough to rot the roots of plants that do not expect any water between spring and autumn.

Santa Barbara daisy, penstemon and various salvias are some of the favorite native perennials. Wax myrtle and the various ceanothus and manzanitas are interesting shrubbery. Western redbud and toyon can be big shrubs or small trees. California sycamore and various oaks are big trees for big spaces.

Start Young Trees Off Right

Recovery is difficult for abused trees.

Young trees are so impressionable. Too much water can damage their roots, or cause them to disperse too shallowly. Improper pruning can disfigure their branch structure, and ultimately compromise structural integrity. Improper staking to keep them stable can actually interfere with development of stabilizing roots, and interfere with trunk development.

Newly planted trees will of course want to be watered from spring to autumn for at least the first year, and more likely for a few years. Those that will eventually be less reliant on watering as they mature are actually the most demanding while young, because their confined roots are not yet adequately dispersed for self sufficiency. The problem is that too much water can keep lower soil too saturated for new roots to disperse into. This causes roots to instead disperse closer to the surface of the soil, which is not only unhealthy for the trees, but puts the roots closer to pavement, other plants and any other features that they can eventually damage as they grow.

Many young trees should be pruned as they grow to eliminate structural problems, and to instead promote good branch structure. The problem is that improper pruning can actually cause structural problems that will be with the victimized trees for the rest of their lives. Pruning should leave no stubs that will take longer to compartmentalize (heal), or that might produce vigorous but weakly attached new stems.

Stakes are unfortunately necessary to stabilize new trees. The problem is that the trees can become so reliant on stakes for support that they do not develop enough trunk strength to support their canopy without stakes. That is why trees should be tied loosely enough to their stakes to be able to move at least a little in a breeze. Nursery stakes (that trees are bound to for a straight trunk in the nursery) should be removed when sturdier stakes are added.

New trees are naturally a bit more distressed than mature trees that have settled into their environment. They are consequently more susceptible to disease and insect infestation.

This Parade Needs Some Rain

Now, this is something you don’t see every day in a chaparral climate.

The lack or rain has really gotten serious! This winter so far has been the driest ever recorded. The past two winters had already been unusually dry. Even when the rain starts, it will be considerably behind schedule. Some seriously torrential rain will be needed to catch up.

As much as we like to think of gardening as something that brings us closer to nature, it demands unnatural volumes of water. Only established native plants or plants that are native to similar climates can survive with the limited moisture that they get from rain. This is why gardens get watered as much as they do.

Lawns of course require the most water because their shallow root systems require such frequent watering, and also because their vast foliar surface area loses so much moisture to evapotranspiration (evaporation from foliar surfaces). Lawns are the first and most prominent of landscape features to succumb to water restriction. Flowering annuals are the next to succumb, because they too want regular watering, especially while they are not getting any from rain.

Fortunately, lawns, annuals and other plants that want an abundance of moisture need less now because they are dormant or considerably less active through winter. Besides, evapotranspiration is inhibited by cooler temperatures, shorter day length, and most of the time, by higher humidity. It is nothing like the warm and arid (minimal humidity) weather during longer days of summer.

Many large and established shrubs and trees can survive quite easily with very minimal watering or even none at all. Established oleander, bottlebrush and juniper may not be as vibrant without watering, but should survive. If they notice a lack of water at all, it would not be until they start to grow again in spring. Mature trees take even longer to notice a problem.

Deciduous plants that are now bare really do not consume much moisture at all and really only need enough moisture in the ground to keep their roots from desiccating. This will only be a problem if the soil is very sandy and drains too efficiently to retain adequate moisture, or if freshly installed plants have not had enough time to adequately disperse their roots into the surrounding soil.

Automated irrigation systems should still be operated only minimally or not at all through winter. However, because of the unusually dry weather, they may need to be used a bit more than usual for this time of year to keep some things from getting too dry.

Watering Trees Is Still Important

Trees in lawns, even drought tolerant sorts, expect to be watered somewhat.

All the optimistic predictions of a rainy winter do not help with the drought yet. Nice warm weather only makes the garden even drier. Many of us have let our lawns dry out, maybe with plans to replace them later. Some have decided to replace lawn with artificial turf, hardscape or other landscape features.

The problem with this is that trees and other large plants that have dispersed their roots under the lawns are thirsty for the volumes of water that they had gotten while the lawns were well watered. They can survive longer than lawn does without watering, and will adapt to less water when they do get it, but they can not do without water completely.

It seems silly to water artificial turf or new decking, but it is sometimes necessary, especially for thirsty trees like willow, ash, elm and redwood. This is why some artificial lawns are outfitted with the original irrigation systems of the lawns that they replaced.

Drought tolerant trees, like certain oaks and most eucalypti, are more adaptable. Of course, those that were originally watered generously are greedier. Those that got only minimal watering may not notice if they get none at all. Regardless of their requirements, they all can be watered less frequently than lawns were, but should be watered generously when they do get watered.

Generous, but infrequent watering soaks into the ground better to satisfy deep roots. It is actually what most trees prefer. Lawn needs frequent watering only because the roots are so shallow. Generous, but infrequent watering uses less water not only because less evaporates from the surface of the soil, but also because less water gets used.

For example, watering weekly for 20 minutes is a generous volume of water, but is still less than watering for 15 minutes three times each week. It is only 20 minutes of watering compared to forty five minutes of watering.

Know The Time To Conserve Water

Automated irrigation is certainly not perfect.

In the wild, plants take water when it comes as rain. Native plants and plants that are from similar climates might be happy to get almost all of their water through winter, and almost none through summer. However, lawns and many other plants want some degree of water through summer. This is why most landscapes are irrigated.

Obviously, irrigation is unnatural. The main disadvantage is that it uses water that must be taken unnaturally from natural sources, which are often, and are presently depleted. The advantages (even during a drought) is that irrigation can be applied where needed, as needed, and when it is most appropriate.

Irrigation systems can be designed to deliver more water to plants that need it, and less water to those that are less consumptive. Watering by hose can of course be similarly tailored to the plants. The volume of water applied can be increased through warm and dry summer weather, and decreased or discontinued through winter.

Automated irrigation can be set to operate very early in the morning when no one is likely to be out in the landscape. The water gets used when the need for water in the home is minimal, so fluctuation in water pressure should not be a problem. If it operates early enough, irrigation can finish before anyone gets out to see it.

Furthermore, early morning also happens to be the best and most efficient time to apply water. Less water evaporates while the air is cooler and more humid. Therefore, more water soaks into the soil. Evapotranspiration (evaporation from foliage) is a bit subdued, so plants cycle through their own moisture a bit slower.

Many plants can just as easily be irrigated in the evening. This would allow even more time for water to soak in before the sun comes up. However, the problem for some plants and lawn is that moisture lingering on foliage all night long can promote the proliferation of all sorts of fungal diseases, including mildew.

Drip and similar irrigation is still the most efficient, simply because water is applied directly, with minimal evaporation. Broadcast irrigation from lawn sprinklers, especially fine mist, is much more susceptible to evaporation. Water evaporates as it gets sprayed through the air, and as it lingers on any wet surfaces.