Rain Will Increase Until Late Winter

The weather is about to change.

Defoliation is the colorful beginning. It indicates that the weather is getting progressively cooler. It then gets messy with the first rain. This is inevitable at this time of year. After all, it is late autumn. Storms will become more frequent as weather simultaneously becomes cooler. So, while gardens are getting wetter, they also take longer to dry between storms.

Ironically, vegetation uses much less moisture while it is so abundant. Deciduous foliage can not perform any evapotranspiration after it defoliates. Evergreen foliage is much less vascularly active while cool. Roots can not utilize all the moisture that autumn and winter rain provides. Soil in some areas might stay moist from now until next spring or summer.

Conversely, summery weather is innately arid and warm. That is how the Mediterranean climate here operates. Moisture is either scarce or abundant. Rain will eventually stop in spring, and then not resume until next autumn. Summer thundershowers are uncommon. Gardening could likely be easier with a bit less rain for winter, and a bit more for summer.

With more rain expected, irrigation needs seasonal adjustment. Such adjustments might need to be incremental, since weather changes incrementally. Manual irrigation might be either less frequent or less voluminous, or both. The same applies to automatic systems, which have a disabling ‘rain’ option. It turns irrigation off without modifying the schedule.

Besides necessitating modification of irrigation, rain can also be messy. It dislodges and accelerates the deterioration of defoliating deciduous foliage. It causes even formerly dry soil to become muddy. A bit too much rain can cause erosion. Cleaning up such mess is less pleasurable while the weather is wet and cool. Then, the weather gets messy again.

Rain can not postpone all gardening. Spring bulbs must get into their garden soil prior to winter chill. Dormant pruning happens later in winter, prior to spring. Fortunately though, gardening is less involved than it is during spring and summer. Maintenance of tools and sorting seed can be indoor tasks for rainy days. So is shopping online for seed, plants or garden tools.

Blue Palo Verde

“Palo verde” translates to “green stick”.

If “verde” translates to “green”, then what color is blue palo verde, Parkinsonia florida? It is simply a bit more bluish green than other species that are a bit more yellowish. Its bark contains chlorophyll to photosynthesize without foliage. Blue palo verde is deciduous so defoliates for winter. Then, it defoliates in response to dryness through much of summer.

Blue palo verde in the wild may develop and retain foliage only during early spring. With landscape irrigation, it can retain some foliage through summer. It can also produce a bit more prior to late autumn defoliation. However, frequent irrigation promotes vigorous but structurally deficient growth. Few blue palo verdes thrive for a century within landscapes.

Blue palo verde can grow almost forty feet tall, but typically grows only about half as tall. It naturally grows as large shrubbery. Removal of lower growth exposes sculptural trunks for small tree form. With staking, trees can develop single trunks. Light yellow flowers are tiny but profuse during spring bloom. Blue palo verde is the Official State Tree of Arizona.

Falling Leaves Are Getting Messy

Deciduous foliage gets messy through autumn.

The primary problem with autumn foliar color is that it eventually becomes quite a mess. Premature shedding started the process even before much of the foliar color developed. Evergreen foliage can contribute to the mess, but most debris now is deciduous. Autumn is, obviously, its season for defoliation. Falling leaves merely do what is natural for them.

Falling leaves fall at different rates. Just as some fall prematurely, some might linger into winter. Also, some that usually linger into winter may fall earlier or later for some winters. Unusually cool, windy or rainy weather accelerates defoliation. However, defoliation can be slower with milder weather. Prolonged foliar color is pretty, but prolonged mess is not.

Besides falling at different rates, falling leaves are quite diverse. Big leaves of sycamore and fruitless mulberry are easy to rake away. Small and abundant leaves of Chinese elm require a bit more effort. They tend to sift between rake tines. Sycamore leaves disperse tomentum that is irritating and perhaps dangerous to inhale. Oak leaves stain pavement.

In a few relevant regards, falling leaves are quite convenient. Their absence allows more warming sunshine through as the weather cools. Not very long ago, they provided shade during summer warmth. Defoliation also allows wintery wind to blow more safely through deciduous trees. Otherwise, such trees would be more susceptible to damage from wind.

Falling leaves are also quite inconvenient. They clog eavestroughs and gutters precisely when they should not. As rainy weather begins for winter, it dislodges even more foliage. Also, it dampens foliar detritus so that it stains concrete and decking more than while dry. Raking detritus is most important while it is most unpleasant because of wintery weather.

Some coarse groundcover, such as Algerian ivy, can absorb smaller falling leaves. Most groundcover or turf is not so accommodating, though. Bigger leaves can overwhelm and shade them, as well as low or dense shrubbery. Slugs and, where they do not hibernate, snails can proliferate within this damp shade. So can fungal pathogens that tolerate chill.

Deciduous Foliage Is Efficient

Maple foliage only seems to be messy because it all falls at once.

(Horridculture will resume on Friday.)

Contrary to popular belief, most deciduous trees, those that drop all their leaves in autumn, are not as messy as most evergreen trees. There are of course a few exception; such as cacti that lack foliage completely, or Italian cypress that drop their finely textured foliage straight down within a very narrow drip-zone, where it decomposes and disappears unnoticed. Very few leaves fall from a big silver maple through winter, spring and summer, so that almost all of the raking is done when almost all the leaves get shed in autumn. However, a big Southern magnolia generally drops leaves throughout the year, so that raking is always necessary.

The problem is that when deciduous trees get to be messy, they are very messy. Also, they get to be messy at the worst time of year, when their leaves mix with rain to clog drains and gutters. Unraked leaves become hazardously slippery when they get wet and start to decompose. It is amazing how something that can be so appealingly colorful through autumn can so quickly become such a nuisance.

Leaves of deciduous trees somehow seem to be better for composting than those of some of the evergreen trees. Anyone with a Southern magnolia knows how slow the foliage is to decompose. Foliage of camphor, bay, carob and various eucalyptus certainly decompose slower than various maple, ash, poplar and birch. Many of us outfitted with green waste bins or curbside collection of green waste prefer to recycle the less desirable evergreen foliage, and compost primarily deciduous foliage. Those of us who do not compost but need to rake under large or many deciduous trees may fill bins for several weeks, or leave very big piles of leaves at the curb.

Small leaves, such as those of most elms, or finely textured compound leaves, such as those of silk tree, jacaranda or locust, may not need to be raked if they fall onto lower shrubbery or ground cover. Small leaves or the small leaflets of disintegrating compound leaves simply sift through the lower plant material to decompose below. However, large elms may produce such an abundance of foliage that some may need to be removed. Maple and other large leaves are not so easy to ignore. They can shade lawns, ground cover or bedding plants, so need to be raked as they fall.

Dormancy Facilitates Survival Through WInter

Deciduous vegetation defoliates for winter dormancy.

Dormancy is not exclusive to vegetation. Many animals are dormant while they hibernate through cold winter weather. Some animals are dormant while they aestivate through hot and dry weather. Fungi and bacteria can maintain dormancy for many years or centuries. Dormancy is a technique for avoiding unpleasant situations, such as cold or hot weather.

Like some animals, fungi and bacteria, some vegetation is dormant through dry weather. This is evident within local chaparral climates and nearby desert climates. Even within a few coastal forests, buckeye defoliates during summer. Such vegetation resumes activity in response to late autumn rain. However, most vegetation here prefers winter dormancy.

Such winter dormancy is especially evident among deciduous species. Many evergreen species merely halt or decelerate their growth, but without defoliation. Several evergreen species defoliate only partially. A few only shed their old foliage as new foliage replaces it during the following spring. Few species prefer to grow most vigorously through winter.

There are a few advantages to defoliation for winter. Wintry wind blows much more freely through defoliated canopies. Evergreen canopies are therefore more vulnerable to wind. In other harsher climates, defoliated canopies do not accumulate much snow. Evergreen canopies might accumulate more snow than they can support. Some get heavy with rain.

Foliage is not as useful through winter as it is through summer anyway. The sun is lower to the south. Consequently, less sunlight gets through more of the atmosphere. Days are shorter while nights are longer. Furthermore, cooling autumn and winter weather inhibits photosynthesis. For deciduous species, foliage becomes less of an asset than a liability.

Dormancy, whether it involves defoliation or not, facilitates a few horticultural techniques. Bare root stock becomes available at the beginning of winter. Transition from its farms to home gardens is much less stressful during dormancy. So is the aggressive pruning that roses and deciduous fruit trees require. Most pollarding is safest during winter dormancy.

Defoliation Is A Messy Process

Defoliating deciduous foliage must go somewhere.

Autumn foliar color eventually gets messy. Actually, any deciduous foliage can become messy during its autumn defoliation. Color is not a prerequisite. Some deciduous foliage remains green through the process. Furthermore, some evergreen foliage contributes to the mess. A few evergreen species shed a bit more as the weather becomes more wintry.

Contrary to popular belief, deciduous vegetation is neater than evergreen vegetation. It only seems to be messier because it defoliates completely at once. Also, such complete defoliation exposes bare stems. Evergreen vegetation sheds slower throughout the year. As it replaces old foliage with new, it sheds more in seasonal phases, but incompletely.

Deciduous leaves also seem to be messier because they are generally bigger. They do not disintegrate into landscapes as efficiently as tiny evergreen leaves do. They require raking from lawns, as well as groundcover that can absorb smaller leaves. So, they fall most abundantly, and dissipate least efficiently. That is why defoliation is so very messy.

Defoliation of deciduous foliage occurs at both the best and worst time of year. It allows more warming sunlight into homes and gardens while the weather is cooling. It leaves deciduous trees more resilient to eventual windy wintry weather. However, it gets messy while the weather begins to get less conducive to gardening. Summer is about finished.

It truly is ironic. Rain and wind will eventually dislodge the last deciduous foliage during winter. Rain is also why this same foliar debris must not clog eavestroughs and gutters. Yet, it is why removal of such debris can be such an unpleasant chore. Removal of foliar debris from hardscapes is also important. It stains and gets slippery if dampened by rain.

While defoliation decreases shade above, it can increase shade below. Accumulation of foliar debris can detrimentally overwhelm turf and groundcover. Some large leaves can do the same on top of dense shrubbery. Fungal pathogens proliferate within the dark and stagnant dampness below such debris. Shade from such debris inhibits photosynthesis.

Defoliation And Dormancy Are Justifiable

Wind blows freely past defoliated stems.

Defoliation and dormancy begin early for quite a few species within desert and chaparral climates. California buckeye can defoliate during the driest summer weather, refoliate for autumn, and then defoliate again for winter. They do what they must to avoid desiccation within their arid climate. Many more species do what they must to survive through winter.

That is why so many plant species are deciduous while they are dormant through winter. They shed their foliage when it is more likely to be a liability than an asset. Like summer dormant plants, they respond to inevitable and potentially detrimental weather. Moreover, they respond to seasonal changes of sunlight as well. Plant species are very perceptive.

With few exceptions, deciduous plants are nonconiferous or broadleaf species. More are endemic to regions to the north and south of tropical regions than within tropical regions. They know that sunlight is less intense and daylength is shorter while the sun is at a low angle during winter. Their defoliation coincides with the least usefulness for their foliage.

Most deciduous plant species are also aware of the sort of weather that they are likely to encounter during winter. Cold and stormy weather with wind and rain or perhaps snow is probably familiar to them. They know that foliage is not only vulnerable to damage, but is also burdensome to associated stems. In colder climates, it can accumulate heavy snow.

Foliage is the source of almost all wind resistance within foliar canopies that suspend it. Such wind resistance causes wind to dislodge limbs or blow vegetation over, particularly while soil is moist from rain. Defoliation eliminates much of such risk prior to the windiest and therefore riskiest storms of winter. Bare stems are more aerodynamic than foliage is.

Defoliation seems to happen at the best time, immediately prior to wintry weather. It even increases warming sunlight exposure during the darkest and coolest season of the year. However, defoliation is also messy while the weather is unpleasant for those who go out to rake it away. Without prompt raking, it clogs drainage of rain while it is most important.

Deciduous Trees Are Not Necessarily The Messiest

This weird Euphorbia is one of the few small evergreen trees that drops no foliage.

Contrary to popular belief, most deciduous trees, those that drop all their leaves in autumn, are not as messy as most evergreen trees. There are of course a few exception; such as cacti that lack foliage completely, or Italian cypress that drop their finely textured foliage straight down within a very narrow drip-zone, where it decomposes and disappears unnoticed. Very few leaves fall from a big silver maple through winter, spring and summer, so that almost all of the raking is done when almost all the leaves get shed in autumn. However, a big Southern magnolia generally drops leaves throughout the year, so that raking is always necessary.

The problem is that when deciduous trees get to be messy, they are very messy. Also, they get to be messy at the worst time of year, when their leaves mix with rain to clog drains and gutters. Unraked leaves become hazardously slippery when they get wet and start to decompose. It is amazing how something that can be so appealingly colorful through autumn can so quickly become such a nuisance.

Leaves of deciduous trees somehow seem to be better for composting than those of some of the evergreen trees. Anyone with a Southern magnolia knows how slow the foliage is to decompose. Foliage of camphor, bay, carob and various eucalyptus certainly decompose slower than various maple, ash, poplar and birch. Many of us outfitted with green waste bins or curbside collection of green waste prefer to recycle the less desirable evergreen foliage, and compost primarily deciduous foliage. Those of us who do not compost but need to rake under large or many deciduous trees may fill bins for several weeks, or leave very big piles of leaves at the curb.

Small leaves, such as those of most elms, or finely textured compound leaves, such as those of silk tree, jacaranda or locust, may not need to be raked if they fall onto lower shrubbery or ground cover. Small leaves or the small leaflets of disintegrating compound leaves simply sift through the lower plant material to decompose below. However, large elms may produce such an abundance of foliage that some may need to be removed. Maple and other large leaves are not so easy to ignore. They can shade lawns, ground cover or bedding plants, so need to be raked as they fall.

Gutters And Chimneys Need Attention

71101thumbThere is no time that is best to clean the gutters on the eaves. They should probably be cleaned early before the debris within them gets dampened by the first rains. However, they will only need to be cleaned out again after more foliage falls. If cleaned only after all the foliage falls, they will be grungier, and there will be potential for some of the debris to flow into and clog the downspouts.

Most of the fresh leafy debris that fell recently is relatively easy to clean out. Debris that has been accumulating through the year will be more decomposed and settled in. Evergreen trees are somehow messier than deciduous trees. They drop smaller volumes of debris in autumn, but they drop the rest throughout the year. Deciduous trees drop all their foliage within a limited season.

That certainly does not mean that deciduous trees can not make a mess. All that foliage has to go somewhere. If the weather gets cool slowly, foliage falls slowly, and for a longer time. Some deciduous trees innately defoliate slowly, and may even wait all winter to finish. Fruitless mulberry, tulip tree and poplars typically defoliate efficiently, making a big mess that gets cleaned up once.

Flat roofs that lack gutters collect debris too. So do the spaces behind chimneys and in roof valleys (where the slope changes direction). Even if this debris does not interfere with the function of gutters and downspouts, it promotes rot in roofing material. Trees and vines that touch a roof are likely to be abrasive to roofing material if they move in the breeze, or hold debris against the roof.

Trees and vines must be kept clear of chimneys, not only because they can interfere with ventilation, but also because they can be cooked by exhaust from the fireplace below, and ignite! Fan palm beards (dead foliage that accumulates on trunks), pine, cypress, spruce and cedar are particularly combustible. Clinging vines can separate brick from mortar, which is another fire hazard.

Working on the roof and gutters is of course potentially dangerous. It might be best to get a professional for these sorts of jobs, especially if trees need to be pruned. While that is being done, there is plenty of raking and other gardening for us to do (without a ladder). Raking leaves is an important job too, since fallen leaves can shade out lawn, ground-cover and flowering annuals.