Summer Rain and other Surprises

We've had quite a bit of rain in the last couple of days. Summer rain is not unheard of in southern California, usually due to chubascos coming up from Mexico like this one, Dolores. However, this was a record-breaking amount of rain. The additional water for our local reservoirs is welcome, and most plants will appreciate it. There are some plants that need a summer dormancy and don't like getting any water in summer. The Fremontodendrons and Ceanothus are examples. Another possible concern is that some plants (such as oaks) are very sensitive to soil pathogens that proliferate when they get a combination of warmth and moisture.  I don't know how my plants will react to this rain. Maybe they will be fine, or maybe it will kill them. Only time will tell. So far everything seems to be doing fine, great in fact.

I was concerned about a Humboldt Lily (Lilium humboldti possibly ssp. occellatum) that I bought in March. Even though it had three big flower buds on it, it was looking pretty dry. The leaves were dry 3/4 of the way up the stem. But I watered it a little and then we got the rain, and it bloomed.

Look at the size of those anthers. They're almost obscene.

A surprise of a different type was a juvenile Black-crowned Night Heron that decided to hang out at our backyard pond one day. Probably roaming around between the lagoons one night and got a little lost. Since they are nocturnal, I think it was just looking for a quiet place to sleep for the day. It looked at the fish a lot but I never saw it catch any. It was gone the next morning.

A more typical pond visitor is this blue dragonfly. I'ts a Blue Dasher, identified by the yellow patch under its abdomen which is barely visible in this photo. I believe this is a male. I didn't see a female around, but hopefully he found one and they hooked up.

Another garden visitor was this Monarch resting on a Thick-leaf Yerba Santa (Eriodictyon crassifolium). The plant is not big enough to bloom yet, so like the Night Heron this guy must have been hanging out for awhile. Fine with me.

I expect some other plants to react to the rain by blooming. We'll see what happens.

Plants vs. Animals

"Befriend the plants and give them aid..."

-Pierre de Ronsard, 1578

I am currently reading In Praise of Plants by Francis Halle'. His central premise is that people have a preference for animals (and he argues that they should reconsider that). I think this is true in general, but like all generalities it isn't true for everyone. After all, the great Linnaeus himself had a preference for plants. When I think back to my earliest memories of nature, I was about equally interested in plants and animals. I grew up in Ventura County. My parents liked to picnic and fish on the weekends, so we were often at places like Wheelers Gorge, the old Lake Matilija (before the dam was cut down), Lake Cachuma, and Lake Casitas. These areas are surrounded by oak woodlands and chaparral. The creeks leading into the lakes have lush riparian woodlands. There were lizards, water striders, ferns, fish, miners' lettuce, sagebrush, quail, sycamores, willows, cottonwoods, dragonflies, tadpoles, and always the massive, gnarled trunks and spreading limbs of coast live oak.

Lake Casitas, Ventura County, photo courtesy of Thewellman

To me, plants and animals, rocks, water and air were always inseparable. That why, when the concept of ecology came to my attention around 1967 it made perfect sense to me. I mean, of course everything is linked together in an interdependent system. How could it possibly be otherwise? It turned out to be a lot more complex than I imagined, but the basic idea has remained unchanged. When we moved into our current house in 1989 I started planting some native California plants. But I didn't just want to have native plants - I wanted to try to emulate an ecosystem that I have loved all my life. That means not only growing the right plants but also emulating natural processes. I'm still working on it.

But getting back to Halle', he studied architecture as well as botany, giving him some unique insights into the architecture of plants, especially trees. The branching of stems, arrangements of leaves on the stem, structure of flowers, placement of flowers, and behavior of roots are not random but governed by genetic programming, as Mendel first elucidated for us. Architecture is a fitting term to describe the process by which plants achieve their genetically programmed size and form. 

For example, tree growth is a trade-off between two very strong tendencies - the tendency towards verticality and the need to maximize surface area of leaves. He estimates that a tree 40 m tall could have a leaf surface area of 10,000 sq. meters (1 hectare). Sometimes on a sunny day I look at the 20 year old coast live oak in my front yard and wonder how many leaves it has at any one time. I have no idea what the answer is, but I like to image them as so many tiny factories, inhaling air and absorbing photons from the sun, converting them to sugar for energy and cellulose for plant tissue. I also think about how long it might live. It should easily outlive me. If someone doesn't harm it, it could easily live into the 22nd century. I like to imagine one of my grand children, or even one of my great-grand children (not born yet) living in this house with this oak tree in 2115.

My oak tree today with the beginnings of its architecture

Halle' also talks about plant movement. Although they can't travel, plants do move a lot - just really slowly. I have always been fascinated by time-lapse photography of plants because it makes it possible for us to see their movement on a time scale that makes sense to us. With the motion speeded up, we see leaves angling themselves toward the sun, flowers opening and closing, stems elongating and jockeying for position. Because they can't travel to attract mates or escape predators, plants have evolved chemical means of doing so. Plants are fabulous chemical laboratories, full of attractive scents and flavors as well as powerful toxins. Again I think about the oaks. Since they are wind pollinated, they have no need for insects to deliver pollen, and yet they are great attractants for insects. Oaks do need a little help spreading their acorns around, notably from squirrels and birds. Below are three photos of the insects that I have seen around my oak tree.

Bark Lice

Some kind of "walking stick" insect

Orange Sulphur Butterfly

The relationship between plants and insects could be described as "complicated", like a human couple that can't decide if they can live with each other or not. Plants lure insects with their colors and fragrances, and in so doing they make insects the unwitting agents of the plant's reproduction. But if the plant is a "host" plant for the insect, then the insect lays it eggs on the plant and thus the plant becomes the unwitting agent for the reproduction of the insect.  The insect's eggs hatch and the larvae of the insect proceed to eat the plant. In the first case the relationship is mutually beneficial. In the second case, the plant is clearly the loser. But in the really, really big picture plants also benefit from this arrangement. Plants and insect can't really live without each other.

Syrphid fly on Tidy Tips

Plants have much greater genetic plasticity than animals, meaning that they produce more mutations and are less troubled by them. One reason for this is that, lacking a true circulatory system, harmful mutations do not spread throughout the entire plant and threaten to kill it. At their worst they merely condemn the meristem that they are part of, leading to the death of a branch, for example. The ability to generate and tolerate mutations ultimately benefits plants. Halle' describes it as "a reserve of variability that plants need to survive in a fluctuating environment from which they cannot escape..." In the love/hate relationship between plants and insects, the ability of a plant to produce mutations throughout its potentially long lifetime enables it to keep pace with the evolution of insect species that may produce hundreds (or even thousands) of generations in the same time span.

Similarly, plants hybridize much more readily than animals, and the resulting offspring are often endowed with so-called "hybrid vigor" or heterosis. Not surprisingly, plants are better than animals for displaying this phenomenon. The greater genetic variability of plants allows hybridization to occur with fewer undesirable effects. Without going into detail (which I don't understand anyway), hybrid vigor appears to result from canceling out genetic "noise" that is naturally present in all species (ScienceDaily, July 22, 2010). Another author gives several examples of plants' ability to use polyploidy ,another form of genetic variability that animals don't easily utilize, to adapt to soils that would otherwise be toxic (Introduction to California Soils and Plants, Kruckeberg, 2006).

In his closing chapter Halle' describes the Two Faces of Botany. There is Botany, the scholarly pursuit which values data and precision, producing a great amount of knowledge but perhaps missing out on some of the intangibles such as beauty. Then there is botany which he describes as "unofficial and alternative, one fully alive and abundant, burgeoning, suckering, polymorphous, and multicolored, eclectic, unclassifiable, erotic, pagan..." While I appreciate the knowledge generated by Botany and I try to understand as much of it as I can, botany is my true love. It's why I prefer gardening to research. As a result, I'll always be an amateur and I'll never know as much as I should, but Halle' has helped me understand that's okay.

I'll finish up with a few things that are blooming now.

Justicia purpusii, Chuparosa. Cape region of Baja

Euphorbia lomelii (formerly Pedilanthus macrocarpus) Slipper Plant or Candelilla. From central and southern Baja.
The flower does look like a slipper.

Ruellia californica ssp. californica, Rama Parda. Also from central and southern Baja

Hazardia sp. from the Channel Islands. There are two species, cana and detonsa and they look very similar.
I don't know which one this is.

Munzothamnus blairii, Blair's wire lettuce. From the Channel Islands.

Epilobium canum ssp. canum (formerly Zauschneria californica). Just starting to bloom now. Loved by hummingbirds.

Chaparral and Scrub Oaks

Continuing with my text-heavy posts, this one will address the chaparral of southern California, particularly San Diego County, focusing on the scrub oaks.

Chaparral covers a very large part of California, even extending up into the warmer, drier part of Oregon and south into Baja. Chaparral vegetation corresponds almost 100% to the area of Mediterranean climate, and this makes perfect sense. Plants of Mediterranean climates are adapted to seasonal drought conditions, somewhat variable and unpredictable rainfall during the wet season, summer high temperatures generally below the extremes of the deserts, and winter low temperature seldom below freezing. The primary stress on plants is absence of precipitation for up to 7 months out of the year (see Plant Life in the World's Mediterranean Climates by Peter Dallman, 1998).

In San Diego and northwestern Baja, the chaparral takes on a unique flavor. This is the most arid portion of the California Floristic Province. However, its proximity to the cool Pacific creates fog and overcast conditions (such as we are having right now) which keep temperatures down and provide a small amount of additional moisture during the summer. Geology also contributes to the uniqueness of the chaparral here. Much of the coastal plain consists of sedimentary rock (sandstone) that has been shaped by successive events of sea level rise and fall, creating marine terraces that are cut by canyons where creeks flow. 

The most rare version of chaparral that is found here is known as Southern Maritime Chaparral. While there is plenty of generic chaparral in San Diego County, certain pockets with the right geology and micro-climate support Southern Maritime Chaparral that includes some rare species, such as Arctostaphylos glandulosa ssp crassifolia (Del Mar Manzanita), Ceanothus verrucosus (Wart-stem Ceanothus), Comarostaphylis diversifolia  ssp. diversifolia (Summer Holly), and Quercus dumosa (Nuttall's Scrub Oak). A few of the more common shrubs are also typically found in Southern Maritime Chaparral. These include Adenostoma fasciculatum var. obtusifolium (San Diego Chamise), Cneoridium dumosum (Bush Rue), Dendromecon rigida (Bush Poppy), Rhamnus crocea (Redberry), and Yucca shidigera (Mojave Yucca). I have designed a large part of my garden around these plants, as well as others that form this distinctive vegetation type.

Yucca shidigera in bloom with Comarostaphylis on the left and Arctostaphylos on the right rear,
also Dudleya virens ssp hassei in my front yard in early spring

Arctostaphylos glandulosa ssp. crassifolia in my front yard. In 1992 I collected this plant as a seedling
from a site in Carlsbad that soon afterwards was cleared and graded to become the Villa Loma Apartments

In 1996 the U.S. Fish and Wildlife Service estimated that approximately 21,000 acres of Southern Maritime Chaparral had historically existed in San Diego County. Due to agriculture and urban development much of that has been lost, leaving somewhere between 1,500 and 3,700 acres at that time (Federal Register Volume 61, Number 195). Because Southern Maritime Chaparral contains no rare animals, persuading the public and the decision-makers to conserve these rare plants is a bit more difficult than it should be.

One of the unique species of this chaparral is Quercus dumosa (Nuttall's Scrub Oak). The City of Encinitas is named after scrub oaks. I assume that some early Spanish explorers or settlers observed a lot of scrub oaks in this area and called it Los Encinitos. These scrub oaks probably reminded them of similar-looking scrub oaks of Spain that are generically called Chaparro, and this term led to the modern word Chaparral. So what species of scrub oak did this early Spaniards see when they arrived in this area? Were they Quercus dumosa or something else?

Herein lies a whole raft of taxonomic problems which I am trying to make sense of but may not be able to. The various shrubs that have been called "scrub oak" at one time or another present a wide variety of leaf shapes, leaf hairs, acorns, and other features. Also, oaks have an annoying tendency to hybridize (perhaps because they are wind pollinated). A number of botanists have endeavored to clarify the distinction between these different types. John M. Tucker tried to sort this out in the 1950s. Beginning in the 1980s there was a renewed effort which is ongoing. Tom Chester gives an excellent treatment of the history of these studies at http://tchester.org/plants/analysis/quercus/scrub_oaks.html, (although he notes that his paper is incomplete). Another paper on this subject is Quercus berberidifolia, Q. dumosa by Janet L. Fryer. 2012. In: Fire Effects Information System, [Online], U.S. Department of Agriculture. Probably the most authoritative paper on the subject is by Kevin Nixon of Cornell University, The Oak (Quercus) Biodiversity of California and Adjacent Regions, USDA Forest Service Gen. Tech. Rep. PSW-GTR-184, 2002.

The gist of these papers, as I understand them, is that all the scrub oaks in southern California were formerly considered Q. dumosa, but there was always a lot of confusion because of the variability in leaf shape and size. It was finally concluded that leaf morphology could not be used diagnostically, but other features could. A process of splitting into multiple species began, so that there are now three species of scrub oak recognized in San Diego County (excluding the desert). These are Quercus berberidifolia, Quercus dumosa and Quercus x acutidens. The last one is theorized to be a hybrid between Quercus englemannii and Quercus cornelius-mulleri (Nixon and Steele, 1980).

Chester says that these species can be distinguished by the size of hairs (trichomes) on the undersides of the leaves. He says that the trichomes on dumosa are easily visible, whereas on both berberidifolia and acutidens they are minute and require greater magnification to see clearly. Nixon adds that the trichomes on dumosa are curly. Everyone agrees that genuine dumosa is restricted to Southern Maritime Chaparral in coastal San Diego County at such locations as Torrey Pines State Reserve. They also say that dumosa is distinctive in several ways, such as very slender, wide-angled stems, which helps to distinguish it from the others. 

This leaves the problem of how to distinguish berberidifolia from x acutidens. Around Encinitas I see many scrub oaks that do not seem to fit the description of dumosa, so they have to be one of these other two. Chester suggests that all the plants called berberidifolia in San Diego County are really acutidens and that acutidens is a sufficiently stable and widespread taxa to merit consideration as a species. He says that he did not see a true berberidifolia until he went to the Santa Monica Mountains. This is consistent with what some others have told me. If this is the case, then everything I am seeing locally that is not dumosa must be acutidens.

I contacted Nixon by email about this dilemma, and he graciously provided some fascinating insights. He notes that x acutidens is fairly common in San Diego County, but he does not say that it replaces berberidifolia, and he still considers it to be a hybrid. I don't know if he is aware of Chester's draft paper, but if so, he is not persuaded by it with respect to the status of acutidens. His most interesting comment is in regard to the acorns, which he has given me permission to quote here. 

"One feature of Q. engelmanni .... is the presence of 
'fused' cotlyedons.  Later in the season, if you cut the acorn of Q. 
engelmannii you will see that the cotyledons form a single mass instead 
of two.  We have used this character in the Q. acutidens populations, 
and it is variable - present to varying degrees in different 
individuals.  This alone strongly suggest hybridity, as it is never 
variable in any other species I know.  In Q. engelmanni it is very 
consistently fused, and indicates a relationship to a group of Mexican 
live oaks that also have fused cotyledons.  This includes Q. arizonica 
as the closest one geographically, but also about 30 other species 
scattered through dry habitats in Mexico. So even though there is 
obvious hybridization with scrub oaks in the 'Q. acutidens' 
populations, Q. engelmannii is clearly part of a different complex." 

So, to definitively identify Q. x acutidens one must cut open a number of acorns late in the season and observe whether some of them have fused cotyledons. 

I have two interests in regard to the scrub oaks. One is to try to understand some specimens that are growing in a chaparral area of Encinitas, the other is to understand what I have growing in my garden. It is clear to me that leaf size and shape are not diagnostic. Yet I am so fascinated by the variety of leaf shapes on these plants that I am going to do a little study of them, below. Perhaps this will just prove the point that leaf morphology cannot be used diagnostically. Perhaps it will also support the notion that what I am seeing in many cases is the hybrid x acutidens. So my sample will consist of two plants in my garden and two plants from a chaparral area in Encinitas. As background, the chaparral area in question is known as Encinitas Ranch. It is mature Southern Maritime Chaparral with a diverse mix of chamise, manzanita, mission manzanita, Yucca, toyon, mountain mahogany, and scrub oaks. It has not burned in quite a while, perhaps 80 years or more. First, an overview shot.

Encinitas Ranch

Scrub Oak #1 is about 8 ft. in height. In the photo the white stick is a 6 ft. ruler. The leaves are fairly uniform over the entire plant, about 1" to 1.5" and virtually all are toothed.

Looking at the undersides of the leaves with a hand lens I can see that there are trichomes but they are very minute and I can't see individual hairs. A microscope would be necessary to make out any detail of the trichomes. There were some partially developed acorns on the plant at this time (early July). Overall leaf shapes and acorns are shown below. I would have been inclined to call this dumosa except that the trichomes don't seem to match what Chester described.

Scrub Oak #2 is located about 50 yards away from #1 and presents a completely different appearance. It is about 6 ft. tall with a more sparse and open appearance. It is sufficiently open to be able to see the base, which was not possible with #1, and it is clear that #2 arises from multiple trunks.

Moreover, the leaves have a completely different appearance. The great majority of leaves are entire (smooth edged) and elongated as shown in this photo. They are still about the same size as the leaves of #1 (about 1.5 inches) but more slender, and this is accentuated by the fact that the edges are smooth and not toothed. The trichomes on the undersides of the leaves appear to be the same as on #1 as far as I can tell with a hand lens.

However, a couple of branches on this plant contain leaves that are toothed. These leaves are probably about 1% of the total leaves on the plant, but it is interesting to note that the plant is capable of producing toothed leaves, and does produce them sometimes. This leaf variability suggests to me that it is a hybrid, but I confess to complete ignorance in how this works. Below are photos of the toothed leaves and acorns. The acorn looks superficially very similar to #1.

Scrub Oak #3 is from my garden. It was sold to me as Quercus dumosa in the strict sense, that is of the type that would only be found at Torrey Pines and similar locations. Unfortunately I don't remember where I bought it so I can't say anything about its origin.

The stems are very slender and widely angled, which is supposed to indicate dumosa. There are trichomes on the undersides of the leaves, not a lot of them and not dense, but they are long and curly or wavy. They are much longer and more visible than on #1 or #2. This plant has never produced any acorns so I can't do any comparison that way. But if trichome length is diagnostic then #3 is dumosa, exactly as it was sold to me. So assuming I now know how to identify dumosa from this plant, let's move on to the next one.

Scrub Oak #4 is also from my garden. It was sold to me as berberidifolia and it was propagated by Native Sons Nursery, so my guess is that it is from central California stock.

The leaf size and shape are very similar to #1 and #3. However, the trichomes on the underside of the leaves are minute by comparison with #3 and very similar to #1 and #2. Is this really berberidifolia? I can only take the word of Native Sons Nursery that they collected acorns from a bona fide berberidifolia somewhere.

CONCLUSIONS
Some months back when I first asked some CNPS people for help in identifying the scrub oaks in this chaparral area of Encinitas, I was told they were all acutidens. This would imply, as Chester contends, that berberidifolia is not found in coastal San Diego County. Personally, I hope this is true as it would make the situation much simpler. All scrub oaks in Encinitas would have to be acutidens unless they have clearly visible, long, curly trichomes.

But of course nothing can be that simple. Calflora shows a large number of locations for acutidens in coastal San Diego County, as well as a large number of locations of berberidifolia, and they overlap completely. The berberidifolia locations are undoubtedly based on reports from highly qualified botanists, so they must be taken seriously. Interestingly, there are no observation points for either species inside the stand of chaparral in Encinitas that I am concerned with. Apparently it has never been surveyed. If both acutidens and berberidifolia are present locally and only the fused cotyledons of some acorns to tell us which is which, then I must conclude that the situation is fairly hopeless for the amateur botanist. I am not expecting to get resolution of this for all of southern California or even San Diego County. I would just like to understand the plants in this one stand of chaparral in Encinitas.

To resolve this I'm going to collect acorns in October and cut them open to look for ones that have fused cotyledons. Since Nixon says that fused cotyledons occur sporadically in x acutidens, I'm assuming I will need to look at quite a number of acorns and they will need to be fully developed. I am also going to try to germinate some acorns to see what kind of leaves I get from the seedlings. Then I'll post my results. Maybe nobody cares but me, but I really want to figure this out.

Observations on California's Flora

Since there isn't much happening in the garden at this time of year, this is going to be a more text-filled post about the origins and characteristics of southern California's native plant communities. I have been doing some reading lately and most of what I'm going to say comes from what I have read.

If we look at California as a whole, it is clearly not a unified entity. There are a number of mountain ranges, a great central valley, and large desert areas. Yet one factor that tends to unify most (though not all) of California is its Mediterranean climate. A biological zone known as the California Floristic Province covers the non-desert portion of the state and is responsible for an impressive level of biodiversity, especially in terms of plants. The California Floristic Province contains more plant species than central and northeastern U.S. and Canada combined. About 47% of the flora of the California Florisitic Province is endemic (see Origin and Relationships of the California Flora, Raven and Axelrod, 1978).

CA floristic province" by NoahElhardt - Own work. Licensed under CC BY-SA 3.0 via Wikimedia Commons - https://commons.wikimedia.org/wiki/File:CA_floristic_province.png#/media/File:CA_floristic_province.png

Along much of the coast of California, the coastline is paralleled by a series of mountains known as the Coast Ranges. These mountains, which run generally north-south, are more than foothills, yet not as high as the Sierras. For much of California, the Coast Ranges lie very close to the sea, as seen most dramatically at Big Sur. Their influence on the flora of California is significant. Where the Coast Ranges are dominant, they capture rainstorms coming down from the north, causing them to unload much of their precipitation onto their chaparral-covered slopes. Their relative lack of flat lands, especially close to the coast, has also affected agricultural and urban and development of this region, keeping the central and northern coast relatively more wild and less urbanized.

The San Andreas Fault System,California, ROBERT E. WALLACE, Editor

U.S. GEOLOGICAL SURVEY PROFESSIONAL PAPER 1515 

Something very interesting happens right around Pt. Conception that begins to give southern California vegetation a distinctly different flavor from its cousins to the north. Near Pt. Conception the Coast Ranges peter out and are replaced by the Transverse Ranges which run east-west. Further south, the Peninsular Ranges resume a north-south line, but much further inland than the Coast Ranges. Complex factors are responsible for this change in geography, including sea level changes over millenia, erosion and deposition over millenia, and the substantial impact of the San Andreas Fault system. The net effect of these factors is to open up a broad swath of low elevation land between the coast and the mountains, as shown in the above map.

The land is question includes what is now the counties of Ventura, Los Angeles, Orange and San Diego, along with the western-most portions of Riverside and San Bernardino Counties. The elevations here are typically under 600 m, and the slope is typically gentle from the seashore up to the foothills. While this topography is certainly not flat and there is much variation at the local level, the overall effect is to allow the marine influence to penetrate very far inland, that distance depending on the precise alignment of canyons and valleys. For example, in Ventura County, the Santa Clara River Valley runs inland for approximately 45 miles to Castaic Junction where the elevation is still only 310 m.

Weather also takes a turn at Pt. Conception. Many winter storms, following the high altitude jet stream, are turned eastward at or before Pt. Conception. The Transverse Ranges play a role in this as well. Of course, some storms do make it further south to deliver rain to southern California, but a quick glance at a map of average annual precipitation shows that there is a definite dropoff in rain south of Santa Barbara County.

Looking at the yellow areas of southern California on the map above, indicating rainfall of 10-15 inches per year, this region of reduced rainfall very closely matches the area of low elevation lands near between the coast and the mountains. In discussing weather, we must also note that the Pacific Ocean along the coast of California is generally cool in temperature because the predominant flow is coming from the colder waters of the north. The currents are complicated and there are many counter-currents and other factors, but the net effect is that the ocean exerts a cooling effect on the climate near the coast, that effect diminishing gradually with distance from the sea. This is just a normal part of the Mediterranean climate dynamic.

Put together a combination of low elevations and gentle topography, plus proximity to the coast and marine influence extending far inland, plus reduced rainfall relative to more northerly California and what do you get? An environment that supports a very unique vegetation with lots of unique species. This assemblage of plants, known as Coastal Sage Scrub, is even more highly drought adapted, high in diversity, and extremely valuable for wildlife. And somewhat surprisingly, the floristic diversity continues to increase as one goes from north to south, toward the most arid part of this region, San Diego.

Coastal sage scrub is perhaps best understood by comparison with the better known chaparral. Although there are a few plant species that are found in both, there are distinct differences between them. In a very general sense, slopes facing north or east tend to be more shaded and thus somewhat better able to retain moisture through the long summer drought. As a result, these areas generally (though not always) support a chaparral vegetation that is evergreen, relatively tall ( up to 12 ft.) and dense. These features, as well as mulch from leaf drop, contribute to the moisture-holding capacity of the soil. This relationship of chaparral to slope aspect is different in southern California than in northern or montane California. In the latter two regions, woodlands are found on north facing slopes and chaparral is found on the sunnier, drier south facing slopes (see Introduction to California Plant Life; Ornduff, Faber and Keeler-Wolf, 2003).

Conversely, slopes facing south and west tend to be warmer and drier, less able to defend against evaporation. This is where we would find Coastal Sage Scrub, consisting of lower growing plants (3-6 ft.) that are less densely  spaced, and often deciduous in summer. Much of southern California was formerly covered with this type of vegetation, and it is extraordinarily important for wildlife. Coastal sage scrub and chaparral are not mutually exclusive and often grow together in a mosaic or patchwork manner, sometimes including open areas of native grasses. Interspersed among the woody and semi-woody shrubs we would find a large variety of herbs, annuals and geophytes. These contribute significantly to the overall floristic diversity. 

Some of the typical species of coastal sage scrub include Artemisia californica, Encelia californica, Eriogonum californicum, Yucca shidigera and Yucca whipplei, various Dudleya species, several cactus species, and many more. Geophytes (bulbs and corms) include members of the genera Calochortus, (Mariposa lilies), Dichelostemma, Brodiaea, and Chlorogalum. Annuals include Eschscholzia californica (California poppies), Castilleja exserta (Owl's clover), various Clarkia species, Collinsia heterophylla (Chinese Houses), various Gilia species, Layia platyglossa (Tidy Tips), various Lupinus species......I could go on and on. In fact, Calflora lists 944 native annuals in San Diego County below 600 m elevation.

Yucca shidigera, Eriogonum fasciculatum and Dudleya lanceolata in Encinitas

Calochortus weedii in Encinitas

Linanthus dianthiflorus at Batiquitos Lagoon, Carlsbad

Unfortunately, coastal sage scrub has suffered from a lack of appreciation by people. Since much of this vegetation goes dormant and drops its leaves in the summer, it turns grey-brown and actually looks dead, although it isn’t. Furthermore, coastal sage scrub occupies land that people find suitable for agriculture or town building. Finally, the vegetation is easily removed compared with evergreen chaparral. So, over the years about 70% or more of the coastal sage scrub in southern California has been removed. In the late 1980s and early 1990s the loss of coastal sage scrub led to the listing of the California Gnatcatcher as a Threatened Species. But that's a long story of its own.

Next time I'll discuss chaparral, especially the fascinating but perplexing scrub oaks.

Coastal Sage Scrub with Encinitas in background