About the Desert Garden, Part 2

A shady spot just after winter rain

Well, it has taken me a good deal longer than expected to write this post!  In this one I am looking at the immediate environs of the small sunny garden.

There are, of course, many different regions within the Sonoran Desert.  There is considerable variation even across the city of Phoenix.  Our patch (and not a small one!) is influenced by the proximity of the Hassayampa River.

Rivers and aqueducts in the desert are fascinating things with their bright waters flowing through barren plains while herons and other water birds trace their courses overhead.  But the Hassayampa River is not like these, being mostly underground with only short sections of flow perennially on the surface.  Its name, in fact, is said to mean the "Upside-Down River" -- a very apt description!

But for all that, the land here does have the feeling of a river valley, a lowland; and when it rains we don't argue with it, having been stranded in our vehicle overnight during one of the deluges of 2014... about a mile from home, with rushing water blocking the road both behind and in front of us.  It was not a dangerous situation so long as one stayed put, but I must admit it required a good deal of patience!  The waters subside about as quickly as they come, but in rainy seasons there is often significant flooding as the excess waters pass through the many washes that stripe and gully the area.  Rainwater seems to move across the soil much further than it penetrates into it.

A second factor, also important to the garden, is proximity to more mountainous terrain.  This allows our temperatures to be a little lower -- both summer and winter -- than areas closer to the city.  Some freezing nights are to be expected; summertime highs are supposedly not as extreme though still hot enough!  The highest temperature I noticed last summer was 114 F/46 C, and we had two stretches of freezing nights during this last winter.

Looking across the nearby ranch at the Vulture Mountains in winter

Quick mountain upthrusts are divided by the flattest of plains.  With this "riverbottom" topography, it is no surprise that much of the soil in these flat lands is fine-grained clay, topped with a rough detritus of gravel and small rock.

 In our nearby washes, this changes to a softer topping of sand or else much heavier rock.

These washes are in turn home to their own tiny ecosystems: little thickets of desert trees and seasonal grasses and wildflowers.  These shift gradually to the creosote and saguaros of the plains, making a varied tapestry across the whole area.

The most common trees in our neighborhood are the mesquite (Prosopis velutina) with its delicate leaves...

...and muted yellow chenille catkins...

...and the Blue Palo Verde (Parkinsonia floridum), which in spring can be a glory of yellow flowers.  (For more on the nearby Palo Verde, which I have written about through most of 2015 with the Tree Following meme, see here.)

Both these trees are legumes and provide important food for wildlife from their pods.

The low-lying areas tend to host ephemeral flowers and grasses.  There are many different grasses, but they are perhaps best looked at as a specimen plant here, growing in tufts and swathes rather than a solid cover.

In moist years there is, of course, the marvelous glow of Kallstroemia grandiflora, known as Calltrop or Desert Poppy, but in fact a relative of the Creosote Bush!

Probably the most common wildflower in our neighborhood is Globemallow (Sphaeralcea ambigua), which seems to thrive even in drier conditions so long as there is some shade.  Brilliant coral orange (there is some variation) flowers bloom on large, gawky plants with soft, silvery, lobed foliage.  Bloom time follows rain, but these seem to be fairly reliable plants even during drier years.  They are offered as garden perennials, though their size limits placement as they can have a tremendous sprawl!

And if you watch carefully, there are the tiny bells of Dichelostemma capitatum, a cormous species which sprouts in the most inhospitable places.

Moving onto even higher ground one finds the iconic saguaro cactus (Carnegiea gigantea), but they are not so frequent here as they are on the rocky hillsides in other parts of the region.  

Carnegiea gigantea, with small scattered shrubs of Larrea tridenta (see below) at their feet

Two other cactus species are common locally: the showiest is the Barrel or Fishhook Cactus (Ferrocactus emoryii), with its brilliant red blooms which open just as summer rains begin.

It is not so spectacular the rest of the year, but still worth looking at and walking carefully around!

At rough estimate, this one is about 3.5 ft (1 m) tall

There are also the Chollas (Opuntia spp.), some of the prickliest of them all.  Unlike the Ferrocactus, these grow happily in the wash in our neighborhood and their pale green blends in with the grasses of the monsoon season.

But in this area the most definitive plant is probably the so-called Creosote Bush (Larrea tridentata).  It spreads (in sparse desert fashion) across the empty areas, forming a shrubby green haze that gives an illusion of verdure.  It tends to be spaced widely, and I have read that it exudes a chemical that inhibits growth of nearby plants, though other sources say nothing about this and it seems to be acceptable for garden use.  

Its fresh, sharp scent fills the air when the weather turns moist.  It grows either low or high, depending on the availability of moisture.  Never (so far as I know) entirely leafless, it puts on a new flush of glossy foliage during wet seasons, then adds some admittedly non-descript yellow blooms...

...later accompanied by silver puffballs of seed.

  And when nearly bare, its striped branches are fascinating in themselves.

As can be imagined, where there is a little more water, there will also be animals.  Lizards are plentiful...

...but we also have a plethora of toad species, from various spadefoots (which I think is the type below) to the Colorado River toad, whose poison glands present a serious danger to dogs unwary enough to pester them.  In moist weather in summer, the air is full of the sound of singing toads!  They do a noticably good job of bug control.  (They may also attract rattlesnakes, which I am not looking at in this post, though they are plentiful...)

Also associated with the presence of water are the dragonflies which occasionally appear.

Happily, there are also plenty of bees!

Bee in Ferrocactus flower

 And I had better not start on birds (particularly since there are many common ones for which I have no photos!)  Just a few...

House Finch, originally native here though it spread across much of the rest of the country during the last century

Curve-billed Thrasher

Female Anna's Hummingbird in the garden

So that is the lie of the land: a dry lowland across which the rain waters have carved themselves innumerable -- and inalienable -- rights of way.    But those same waters make for a fascinating wealth of plant and animal life.  And as the plants think it is a more hospitable area to grow and bloom, it must be a good choice for a garden!

About the Desert Garden, Part 1

Saguaro cactus (Carnegiea gigantea) against a backdrop of the White Tanks mountains

Although I'm still hoping to get a vase up on the blog this week, I am taking some time out to work on a post that I've been planning for a long time - several posts, in fact.  I've wanted to take a long look at where the garden is located, to give some idea of the larger context and of the various factors affecting its growth.  This is the first of what will probably be three posts, each coming closer to the garden itself.  And when I am finished, I intend to edit and combine the three to make a more intelligent "About" page for the blog!

It's been over a year since I started the small, sunny garden.  In the meantime I've learned a lot about the location and some of its idiosyncrasies.  To begin, the garden resides just on (or beyond, according to many locals!) the northwest edge of the Phoenix, Arizona, metropolitan area.  This places it in the northern section of the Sonoran Desert.  So I'll begin with a look at this wider area.

The Sonora is the hottest of the North American deserts and at the same time contains the largest diversity of plant species.  Native Sonoran plants range from the Saguaro cactus (Carnegiea gigantea, which occurs in the wild only in this desert) to riverbottom trees such as Arizona ash (Fraxinus velutina), to a host of shrubs and subshrubs and herbaceous wildflowers.

Carnegiea gigantea, the gentle giant of the Sonoran Desert

Larrea tridentata, the shrub which lends its distintive, crisp scent to moist days

Sphaeralcea ambigua, whose warm cup-flowers enliven the roadsides after rain

It is a large desert, encompassing sections of southeastern California, much of southern Arizona, and 

northwestern sections of Mexico, where it extends at least to the Gulf of Baja (Baja California itself is now considered by many to be a separate ecosystem).  Throughout this desert there are multiple subdeserts and a wide range of elevations, with the lowest point being California's Salton Sea, which lies below sea level.

There are now some major cities in the region, with Phoenix being the largest -- and a rapidly-expanding one.  Others include Tuscon, AZ, and Palm Springs, CA, as well as Hermosillo and Saltillo in Mexico.

The region is home to a number of native American tribes; but the Hohokam, who originally erected irrigation canals in the Phoenix area, left them during the 14th century, as massive flooding and associated alterations of the Salt River destroyed the system or rendered it unworkable.  The canals then lay more or less unused until the 19th century.  As settlers and prospectors entered the area in the 1840's and '50's, the ancient canals were promptly repaired and expanded, providing arable land for crops of hay, cotton, citrus, etc.  These supplies went to Fort McDowell to the northeast and to Vulture Mine to the west.  Vulture Mine was the richest producing gold and silver mine in Arizona; shut down with other gold mines during the Second World War, it failed in a later attempt at a comeback and remains closed to the present day.  In the meantime Phoenix became a transport and agriculture hub and eventually a major metropolis on its own account, growing out into the surrounding desert at a great rate.  Job and retirement opportunities have fueled much of the growth, and the sunshine is offered as respite from cold, grey winters elsewhere in the country.

Cattle-ranching has also been a major factor

The weather itself is part of what defines the region.  During autumn and spring and part of winter, it makes the garden here feel like an outpost of Paradise.  In the dead of summer one is apt to compare it to the other place.  Summers are proverbially hot, with many days reaching over 100 F/38 C and extended periods of temperatures over 110 F/43 C.  (A record 122 F/50 C was reached in Phoenix on June 26, 1990.)  Low humidity makes it more bearable for the humans, but not for plants!  Winters, on the other hand, are mild, with a smattering of freezing temperatures, greater as one moves beyond the city to the north.  This limits the use of tropical plants, but still allows citrus to be grown through much of the area.

Rain is, of course, scarce -- about 7 in/18 cm annual rainfall on average -- and occurs over two separate periods during the year.  The largest amounts come in the summer monsoon season, the first relief from the searing heat of June.  Though temperatures in July and August remain high, the rain and associated humidity offer a respite to plants (and mosquitoes!).  The second period is during winter.  But the rainfall is in any case too widely spaced to sustain grass cover, let alone heavier vegetation.  The soil is basically dry; and without the water to flush mineral build-up away, it is often alkaline and to some degree salty.

Soils can range from sandy and rocky to clay.  In some locations, such as hillsides, it can include caliche, which is a layer of calcium carbonate hardpan.  Thin layers can be broken up; thick layers (sometimes over three feet deep) present a serious challenge to plant-growing.  Clay replaces lighter soils as one moves away from mountains.

There are many mountainous upthrusts across the area.  These are the Vulture Mountains, which take their name from the Vulture Mine

But the most important factor in many ways is simply the sun.  Almost ever-present (Phoenix boasts an average of 330 days of sunshine per year), it is also very intense due to the latitude and low humidity.  This is no longer the "full sun" of standard gardening nomenclature, but a thing to itself, requiring a sharp lookout as many plants require some protection from its full force.  This, in turn, makes shade a unique opportunity for the gardener, allowing the use of plants beneath plants, using species that would never tolerate such conditions in more northerly locations.  Even many succulents, including aloes, require some shade here for best growth.  And in some cases, for survival.

All of which creates the unmistakable growth patterns of the Sonoran Desert.  Scrubby desert shrubs spaced sparsely across rocky or gravelly hillsides and plains.  Thickets of little trees in low areas, leafless in the drought of summer, but flourishing in the rains that flood across the land periodically.  Tall stands of cactus looking out at the sun.  Low-growing agaves, whose shallow roots collect the water where it is -- at the surface -- and whose heavy leaves store the water against the many dry days ahead.  Sweeps of wildflowers that suddenly bloom, then dry and blow away on the ever-present wind.

Kallstroemia grandiflora was abundant during the exceptionally wet summer of 2014

I love this place.  I love the confounding brilliance of the daylight, with its flattened hues and clean-cut shadows.  The way the earth changes from gold to grey to gold again with the passing of a single cloud.  I love the sense that one can lean against the sun -- it's so close here -- to get warm.  And the cleanness of desert soil, washed daily by sunlight and kept scoured by wind and flood.

It is a beautiful land.  But certainly it is an intimidating one for the gardener.  And information must be collected haphazardly as one finds books and knowledgeable gardeners because there is simply not the storehouse of old wisdom nor centuries' worth of gardening tomes.  I am collecting my own little storehouse -- one year's worth now -- here on the blog.  It's already been wonderful to be able to go back and check my own records and theories; and perhaps it will be helpful or at least interesting to other gardeners, in the region and out of it!

Looking up at a Saguaro cactus (Carnegiea gigantea)

The Wild Tree: November

I have been very slow to go around and check on the wild Palo Verde tree (cluster of little trees, really) that I'm watching for the Tree Following meme.  I assumed that there would be little change from last month, which is true, but there are some things to notice in November.

First, of course, it does not lose its leaves for the winter, which is relatively mild here and generally a good time for the plants.

So it is still fairly well-foliaged, with the occasional yellow leaf here and there.

More surprisingly, I spotted a stray bloom as I looked up into the canopy.  At first I thought it was only another yellowed leaf, but, no...

Here it is, a little closer, with its bright yellow petals and brilliant russet stamens...

There have been other spare blooms over recent months - no doubt why I found a couple of immature seedpods as well as a fully ripe one still on the tree.

The beautiful grey-green bark from which the species derives its common name of Blue Palo Verde (which translates very roughly to "blue green pole..." - "palo" seems hard to translate!) remains largely unchanged across the months, with wonderfully smooth-skinned branches behind a loose veil of tiny leaves...

...a few of which showed signs of having been munched...

...and some were folded today.  I don't know why, as we're not getting extreme temperatures in either direction at present.   But perhaps the tree is like me and finds it difficult to adjust to nights in the forties (Fahrenheit this time!) after a summer's worth of heat?  

But it's certainly beautiful weather, and the trees are thriving.

I hope I can still link this post to the meme, now kindly hosted by Pat at Squirrelbasket.  Thank you, Pat, for carrying on this wonderful idea!

Weather Diary: Sunny; High: 71 F (22 C)/Low: 42 F (6 C)

A Wildflower for Wednesday

 Although I have had some wonderful gardeners in my family, the gene did skip a generation coming to me.  My mother has never been overly interested in gardening (though certainly supportive of my efforts).  However, she has always been fascinated by the wild plants and animals to be found in the various place we lived.

This has had its influence on me too.  I have been known to indulge in the dubious (from a gardening perspective) practice of leaving a wildling to grow "to find out what it is".  Generally, it was not something to be recommended for a civilized garden!

This, though, is a different case.  I know that the plant in question is Pectis papposa, familiarly named Chinchweed.  It is an annual which grows on disturbed sites here in the Sonoran desert.  It blooms in late summer/early autumn, and the garden site had plenty of it when I began clearing.  And frankly, I am playing with litte Pectis papposa.

I may regret it later, but I have not found it a difficult plant to remove, unlike some of the other pests which grow around here!  I am using it as a temporary groundcover in areas where it is arriving as the season progresses.  In a few months it will dry out and blow away - or at least that was the pattern last year.  It's taking a bit of a chance, I know, letting it settle in under a rose bush, in this case "The Alnwick Rose".

It has a nice scent to the leaves: a fresh herbal scent that still somehow warns "Don't eat me."  If I were a horse or cow - or a rabbit, perhaps - I would certainly leave it alone.  Our neighborhood, which consists largely of open desert, was full of this fragrance during a few weeks last autumn.

Well, we shall see whether this is a Bad Mistake or an Underused Native Annual.   Its friendly colours and airy habit are rather cheering in the oppressive moods of August.  So I hope it will be the latter!

Weather Diary: Hazy; High yesterday: 95 F (35 C)/Low: 82 F (28 C)

The Garden Olla Project, Part 1

Let me explain.  I am a potter with a garden.  And presently I live in a region with a unique history of earthenware pottery.  It is a mixture of the Pre-Colombian tradtion and the old Mediterranean tradition, coming together to create various forms, from Native American to Mexican to the American ranch pottery.  So it has been irresistable to temporarily leave off working in my much-loved stoneware to develop my own earthenware clay and play around with the forms and uses it inspires.  A light-hearted look at classical Greek pottery, for instance...

But at last I had to try out a very traditional idea for the garden.  Across the Mediterranean lands and into the American Southwest, the basic, unglazed, earthenware pot - the same sort used for cooking casseroles in southern France, for instance - finds an additional use in the garden.  As a slow-release water reservoir.

This is due to a unique feature of these low-fired clays.  They are slightly porous.  (This is, after all, the same clay used for flower pots.  This is why clay flowerpots "breathe".)  Pour water into an earthenware pot and it will quickly soak into the fabric of the clay, turning it to a darker red.  Wait a while longer, perhaps half a day, and you will find a little pool of water beneath the pot.  Often this not desirable, which is one reason why glazes are applied on earthenware.  Glaze, with its fully melted glass-surface, renders the pot non-porous.

However, time out of mind, there have been uses for which the porosity was indispensable.  A water-filled jug is kept cool by surface evaporation.  Objects immersed inside remain cool, even in high temperatures, and especially in a dry climate.  Drinking water is kept cool.  And in the garden, the seepage itself can be used to slowly release water to the roots of thirsty plants.  There is minimal water loss as the pot is buried in the soil itself, allowing all the water to flow into the plants' root zones.

Many traditional ollas (as these pots are known in Italian and Spanish) are large, containing 2 gallons or more of water.  Mine... well, they are not very big.  Just some small jars to test the idea and hopefully extend the necessary time between waterings as summer warms up.

The idea is to dig them into the ground near the plant's roots, covering all but the mouth, then fill them with water.  Simple, I think!

I am finished with part one of the task: making the pots.  Handthrown on the potter's wheel, then dried...

...then placed inside the kiln...

Then fired to around 1045 degrees C (about 1915 F).  Ready to... plant.

So far, so good.  Part two will see them in the ground!