Arid Weather Increases Water Consumption

Chaparral vegetation naturally tolerates arid weather.

Superbloom is brief for two main reasons. It involves native species that know to bloom quickly before arid weather of summer. Also, wildflowers in the wild receive no irrigation to sustain bloom through arid weather. With irrigation, some of such species are capable of prolonging bloom. A few can disperse seed for subsequent generations to bloom later.

That is why California poppy blooms for a longer season within home gardens. It easily performs through much of summer with irrigation. Also, with irrigation, it might regenerate to bloom for autumn after summer dormancy. Seed from earlier spring bloom might grow to also bloom for autumn. Some godetias and lupines perform similarly within cultivation.

Most species within home gardens are exotic though. In other words, they are not native. Those that are native to a similar mediterranean climate respond similarly to cultivation. Generally, some from desert climates do so also, although many dislike extra irrigation. The majority of exotic species actually rely on some degree of cultivation and irrigation.

Such species are native to climates with cooler and less arid weather through summer. Rainfall here is too limited to winter to sustain them through summer. Minimal humidity and warmth increase the need for moisture while it is least available. Cooling summer breezes actually accelerate desiccation. Arid weather certainly has its disadvantages.

As spring relinquishes to warmer and drier summer, irrigation becomes more important. Frequency and duration of automated irrigation must adjust to increasingly arid weather. Shallow root systems, such as those of turf grass lawns, require more frequent irrigation. Deep root systems, such as those of maturing trees, require more voluminous irrigation.

However, irrigation should not be so excessive that soil remains saturated. Many mature trees and shrubs need none at all. Some receive enough from what adjacent vegetation does not consume. Some are satisfied with only occasional irrigation. Turf and annuals require the most frequent irrigation. Yet, even they can rot if their soil is always saturated. Calibration of irrigation requires diligence.


Superbloom Highlights Local Mediterranean Climate

Rosemary can bloom longer with irrigation.

It does not happen often. The average frequency is about ten to fifteen years. However, it occurred in both 2017 and 2019, prior to this spring. That is enough for thirty to forty-five years! The current superbloom is only now finishing locally. It may continue through most of May near the coast farther North. The best bloomers enjoy the Mediterranean climate.

Climate is the typical and seasonal weather pattern of a region. The local Mediterranean climate is typically mild and somewhat arid. Almost all rain occurs between late autumn and early spring. Rain is otherwise rare. Winters are cool but not too cold. Summers are warm but not too hot. Native and some exotic flora knows how to exploit such climates.

Some exotic flora that prefers other climates also seemed to demonstrate a superbloom. Some merely responded to the unusually cool weather last winter. They appreciate more vernalization than they typically experience here. Some species enjoyed the unusually abundant rain last winter. Some species enjoyed both extra rain and extra vernalization.

Native species and exotic species from similar Mediterranean climates are a bit different. Their superbloom happens at the same time, and is also a response to earlier weather. However, it is also a response to later weather. They know that Mediterranean climates get warm and arid through summer. They are in a rush to finish blooming while they can.

Superbloom is how many species accomplish all their annual bloom within a brief time. They begin as soon as cool and stormy wintry weather finishes. They finish before warm and dry summer weather desiccates their flowers. Of course, such bloom may not be so spectacular after typical winters. It is only superbloom after exceptionally wintry winters.

Some species that exhibit superbloom in the wild bloom later for irrigated home gardens. This includes some exotic species from similar Mediterranean climates elsewhere. Such climates are present in small portions of Australia, South America and Africa. Obviously, most Mediterranean climates are around the Mediterranean Sea. Most exotic plants that are most adaptable here are from such climates.

Shasta Lake

Shasta Lake is a large reservoir on the Sacramento River. It contains water for flood control and to generate electricity. Some of the water within is used for agricultural irrigation and, to a relatively minor degree, to supply regional municipal water.

It is a very common misconception that the volume of water within Shasta Lake is necessarily relative to ‘drought’ conditions. Low water level is supposedly indicative of a ‘drought’. High water level is supposedly indicative of ‘normal’ weather conditions, including adequate precipitation. This same misconception seems to apply to all reservoirs in California.

Well, after the rainiest winter since 1982 and 1983, Shasta Lake is still not full. The level fluctuates, so might have been full earlier, or might be full later, but regardless, is not presently full. Water must be released prior to expected rainy weather, which can still occur during spring, in order to accommodate more water to control flooding. Less water may be released as drier weather is expected. Shasta Lake could therefore be fuller or completely full for summer, when almost no rain is expected. The presently observed water level does not indicate deficiency of water any more than a potentially higher water level during summer indicates surplus.

Most of California has a chaparral climate. Some of California has a desert climate. Such climates are naturally dry through summer. It is quite normal. It does not constitute a drought. A drought is an unusually dry weather pattern. It is not so normal.

Contrary to popular belief, California is NOT in perpetual drought. Although droughts occasionally happen, they are not annual events. Dry weather that occurs annually every summer is normal climate. If there is a deficiency of water here, it is because there are nearly forty million people relying on a limited supply of water.

Horridculture – Horrid Weather

Alviso in 1983

This is no horticultural gripe, as is traditional here on Wednesday. Actually, it is not much of a gripe at all. It is merely a brief description of the unpleasantries of the current situation here.

Rain is predicted to resume prior to two this morning, and continue almost until tomorrow evening. It is expected to be remarkably voluminous. Strong wind that begins about eleven is expected to continue for a bit more than a day, until about two tomorrow. The ground is already saturated from the major storm on New Year’s Eve, and minor rain afterward. Rain may pause only for Friday, but may then resume for the foreseeable forecast.

This weather could be the worst since the winter of 1982 and 1983. If so, the results would be worse now than they were then. So many more people live here and nearby now. Flooding, mudslides and everything that stormy weather causes will affect many more people than ever before.

The area across the road from here is to be completely evacuated in the morning because of expected flooding. It already flooded on New Year’s Day. A parking lot nearby is already full of cars from that neighborhood.

The burn scar from the CZU Fire two years ago has not yet recovered, so is unusually susceptible to erosion and mudslides.

This sort of weather may be no more than what is normal in ‘average’ climates. It is just more than we are accustomed to in the mild climate here. As I schedule this to post at midnight in about a quarter of an hour, the weather is still pleasant, without indication of what is predicted.

I should get some sleep now. The crew and I will likely be very busy in the morning, and exhausted, cold and wet by noon.

Rain Initiates The Rainy Season

Weather generally conforms to the seasons.

Seasons here may seem to be less extreme than they are within other climates. Summer warmth is rarely too hot, and when it is, it does not continue for too long. Winter chill may be insufficient for some plants that rely on it to sustain their winter dormancy. Autumn and spring are as notable for the first and last seasonal rain as for colorful foliage and bloom.

This is actually very relevant within local chaparral climates. Rain and lack of rain define seasons here as much as extremes of temperature. Where the traditional four seasons of winter, spring, summer and autumn merge so softly, the rainy season and the dry season generally do not. Rain begins abruptly in autumn, and ends almost as abruptly in spring.

Consequently, home gardens can get inhospitably dry without adequate irrigation during more than half of the year. Then, they may require no irrigation for almost half of the year. Warm weather that coincides with the dry season enhances aridness. Cool weather that coincides with the rainy season enhances dampness. Mild climates can get extreme too.

Recent rain ended both the dry season and the fire season, and began the rainy season. For many plants, irrigation will be unnecessary until the dry season resumes next spring. Plants that continue to require irrigation will require much less, and only as their soil gets dry during prolonged lapses of rain. Therefore, automated irrigation requires adjustment.

Potted plants, bedding plants and young plants with minimal root dispersion will be more likely to want watering during warm lapses of rain. Substantial foundation plants beneath eaves generally extend roots beyond sheltered soil, but some do not. Also, potted plants under eaves of porches are unable to reach rain moistened soil with their confined roots.

While diminishing the need for irrigation, rain can be messy. It is, of course, wet. It makes soil muddy. Runoff can cause erosion. Stormy weather, which typically involves both rain and wind, dislodges copious foliar debris. Such debris accumulates while no one wants to go outside during stormy weather to rake it. Inconvenient timing seems to be a pattern. Yet, rain is undeniably gratifying.

How To Deceive Smart Seeds

Some seeds need help to germinate.

Plants could not proliferate as they do if they were as unintelligent as they seem to be. Actually, much of their activity would be considered quite ingenious if it could be observed in a more ‘human’ perspective. From their exploitation of pollinators to their aggressive tactics for competition with other plants, the behavior of plants is obviously very deliberate and purposeful.

Because they are so reliant on the weather, pollinators and so many other environmental factors, the life cycles of plants are on strict schedules. They must also adapt to diseases and all sorts of other pathogens. Fires and grazing animals are problems for many, but advantages to most.

Most seeds develop during summer and autumn. When they fall to the ground, they need to know to delay germination until spring to avoid frost and the likelihood of getting eaten. Seeds of many plants, particularly those from more severe climates, germinate only after being ‘stratified’ by a specific duration of cold weather. Such seeds need to be artificially stratified by refrigeration in order to germinate any differently from their natural schedule, or where winters are not sufficiently cold.

Many seeds require ‘scarification’ by digestion by animals that naturally eat them, or by the quick heat of a wildfire, to break or soften a hard outer coating that otherwise inhibits germination. Seeds that need to be digested actually rely on animals for distribution. Seed that need heat want to be the first to regenerate after a wildfire, before competing plants recover.

Goldenrain tree, and many maples and pines produce so many seeds that even if less than one percent germinate in the garden, they seem to be prolific. However, for more reliable germination of a majority of seeds, they should be scarified. The seeds of many pines that crave fire can be heated briefly in an already hot oven to simulate fire, just enough to heat the seed coat without roasting the seeds. Some people actually prefer to spread them on a piece of paper, and then burn the paper. Seeds that only need their hard outer coating to be damaged slightly might need only to be sanded lightly on sandpaper. I actually prefer to rub my canna or Heavenly bamboo (nandina) seeds on a brick or bit of sandstone.

Arid Climates Can Be Challenging

Some plants shrivel in arid warmth.

‘Mediterranean’ translates as an adjective that describes being at the middle of the Earth. Those who inhabited that region many centuries ago considered the Mediterranean Sea to be central to their World. That was long ago and far away. Nonetheless, climates here and now are somehow Mediterranean. Maybe semi arid climates of Italy are Californian.

Mediterranean climates are temperately warm with dry weather through summer. Rain is almost exclusive to a rainy season between autumn and spring. Although rain can briefly get abundant during the rainy season, the average annual rainfall is modest. Humidity is minimal for much of the time. Arid warmth is more comfortable than rarely humid warmth.

Desert climates accumulate less than ten inches of rain annually. Local climates receive more than fifteen inches of rain annually. They are therefore not sufficiently arid to qualify as desert climates. Technically, they are only semi arid chaparral climates. This climactic designation is perhaps more appropriate than the regional designation of Mediterranean.

Native plants and plants that are native to other chaparral climates are naturally pleased with the local climate. However, some initiate at least partial dormancy to survive through the long and arid summers. They may bloom early, but then partially defoliate for several months. Some delay dormancy if watered. A few dislike watering. It is unnatural for them.

Most plants in home gardens are not native to chaparral climates. They require watering to compensate for aridity during summer. Minimal humidity accelerates evaporation from foliar surfaces, which increases the demand for moisture. In conjunction with warmth and wind, aridity can desiccate foliage. Like people and pets, plants must maintain hydration.

Humid warmth that is less comfortable for people and pets is more comfortable for plants than arid warmth is. Humidity inhibits evaporation from foliar surfaces so plants consume less moisture. Incidentally, most pathogens, such as fungal diseases, bacterial diseases and most insects, also prefer warm humidity. People and pets seem to be in the minority.

Give Plants What They Want

Flowering crabapples are generally reliable for profuse bloom, but some varieties might perform and grow better where winters are cooler.

Dogwoods are certainly pretty as they bloom this time of year. They are rare, but seen often enough in nurseries to make one wonder why they are even more scarce in local gardens. Those that got sold in previous years should now be prominent features around town. The problem is that because they are not happy in local climates, dogwoods become dogwon’ts. They won’t bloom. They won’t provide good fall color. Many won’t even grow. Dogwoods prefer more humidity, so in local gardens, want to be sheltered from full sun exposure and drying wind by larger trees or buildings.

Nurseries generally stock plants that are appropriate for local climates. A few nurseries also have a few plants that would rather be somewhere else, but can be grown with certain accommodations. Reputable retail nurseries are generally careful to divulge which plants need more attention, and what their requirements are. However, many of the big garden centers in home improvement stores are more interested in selling what they can rather than selling what is actually appropriate, particularly since they thrive on turnover and replacing plants that do not survive.

Not all plants are as easy to grow as junipers and oleanders are. Japanese maples and rhododendrons like at least some degree of shelter from direct sun exposure and dry heat; but the California fan palm thrives in wicked heat. Plumerias and coleus can be damaged by even slight frost; but many apples and pears want more frost. Spruces like even moisture; but many yuccas rot without enough dry time.

This is why it is important to know how to accommodate plants that may be less than ideal for local climates. Those of us who choose to grow plants that have special needs should at least give them what they want if we expect them to perform as we want them to.

Warmth Accelerates Early Spring Bloom

Deciduous fruit trees should remain dormant.

Unseasonable warmth and dryness has been great this winter. Such weather is often an advantage of this locally mild climate. Chill never gets too harsh. Rain does not continue for too long. However, even by local standards, the weather has been unusually dry and warm for quite a while. Although appealing to people, it can get disruptive horticulturally.

Obviously, a lack of rain eventually becomes a lack of moisture. Some evergreen plants, potted plants, ground cover plants and lawns may already need watering. Although rain, or lack thereof, does not affect availability of water from municipal sources, it determines when irrigation with such water becomes necessary. It will be sooner than later this year.

Obviously, warmth accelerates this process. It draws moisture both from intact evergreen foliage and the soil below. (Dormant deciduous plants still do not lose as much moisture without foliage.) Unseasonable aridity (minimal humidity) and wind intensify the effect of unseasonable warmth. Desiccation is not the worst consequence of the weather though.

Unseasonable or premature warmth might stimulate premature spring bloom and growth. This can be very disruptive for plants that rely on sustained chill to maintain their minimal dormancy requirements. Peonies that are marginal where they normally experience their minimal chill requirements might be dissatisfied with inadequate chill through this winter. 

Even for plants that do not require much or any chill, premature bloom can be vulnerable to normal aspects of wintry weather if and when it resumes. Flowering cherry trees might bloom during sustained warmth. Such bloom would be quite susceptible to damage from resuming winter rain. Resumed chill might stall premature magnolia bloom until it molds. 

Prematurely developing fruit, accelerated by unseasonable warmth, is also vulnerable to resumption of wintry weather. Heavy rain, which is still possible through the remainder of winter, can dislodge freshly pollinated flowers, or small fruit as it begins to develop. More developed fruit is vulnerable to rot or mold during cool and damp weather prior to spring.

Frost Damage Is Not Cool

Frost damage is a cold reality.

Frost happens. It may not happen every winter. It may not happen everywhere. For a few of the mildest climates, it may not be a major concern. For some climates though, it might have potential to cause significant problems. The best means to avert frost damage is to avoid plants that are vulnerable to a degree of frost that is normal for a particular climate.

Of course, that is not as simple as it sounds. Even in mild climates, angel’s trumpet might get shabby from chill that is not cold enough for frost. Where weather gets cooler, familiar plants such as bougainvillea, avocado, lemon, fuchsia and pelargonium may experience frost damage. Such plants necessitate certain precautions, and must assume innate risk. 

Some plants that are susceptible to frost damage can live in portable pots that can move to sheltered situations prior to frosty weather. Some might be houseplants that live in the garden for part of the year, but come inside at least for winter. Eaves, particularly if above walls of heated buildings, may be adequate protection for marginally susceptible plants.

Plants that are susceptible to frost damage, but live in the ground or are too big to move, may need temporary protection from frost. Such protection might consist of tarps, burlap, old sheets, plastic trash bags or cardboard, suspended above by stakes and string. Thin materials, such as sheets or trash bags, can freeze through, so should not touch foliage.

Protective tenting materials should not remain over sensitive foliage for too long. Ideally, they should be in place immediately prior to frost, and then gone immediately after. Since frost occurs at night here, protection is useful only overnight. During daytime, it obstructs sunlight, but collects heat to stimulate new growth that is more sensitive to frost damage.

Many plants are too big to protect. Fortunately, bigger plants are less susceptible to frost damage than smaller plants. If possible, outer foliage that succumbs should remain until the local last frost date. Although unsightly, it shelters inner growth. Moreover, premature removal of frost damage stimulates new growth that is even more susceptible to subsequent frost damage.