Welcome to the small, sunny garden! It was born into a bare patch of desert dirt back in autumn of 2014. It spills off the edges of our patio and reclaims a bit of the surrounding desert for habitation: for us, for the hummingbirds and bees and butterflies and lizards and toads and, must I admit, rabbits!
Here is a look at the setting and the creation of this little desert garden.
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.
The Sonoran is the hottest of the North American deserts, yet it contains the largest diversity of plant species (a fact worth noting by the gardener), from the iconic Saguaro cactus (Carnegiea gigantea) to riverbottom trees such as Arizona ash (Fraxinus velutina). It is a large desert, encompassing sections of Arizona and California in the US as well as much of northern Mexico.
Within this vast and still very sparsely inhabited region, a number of cities have grown up: Phoenix and Tuscon in Arizona, Palm Springs in California, and Hermosillo and Saltillo in Mexico.
The region has long been home to a number of native American tribes, and many centuries ago the Hohokam erected irrigation canals along the Salt and Gila Rivers, allowing them to raise extensive crops of such staples as maize, squash, beans, and cotton. These canals were eventually abandoned -- experts appear to differ as to why -- and the Hohokam settlements scattered and dwindled by about 1450.
As settlers and prospectors entered the area in the mid-1800s, the ancient canals were discovered and promptly repaired and expanded (hence the name of the city, "Phoenix"), providing arable land for crops of hay, cotton, citrus, etc. The irrigated region became an agricultural supplier to the army at Fort McDowell, as well as to the richly producing Vulture Mine to the northwest. Eventually, however, Phoenix became a major metropolis on its own account, growing out into the surrounding desert at a great rate.
The weather is a major factor of life here, and certainly of gardening. During autumn and spring and much of winter, it makes the garden feel like an outpost of Paradise. In the dead of a long summer one is apt to make the opposite comparison. 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 on June 26, 1990. Low humidity makes it more bearable for the humans, but not for plants! Winters 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 8 inches (20 cm) annual rainfall, and occurs over two separate periods during the the year. The first is the summer monsoon season, the first relief from the searing heat. Though temperatures in July and August remain high, the rain and associated humidity offer a respite to plants. The second period is during the cool, wet winter. But the rainfall is in any case too widely spaced to sustain grasslands, let along heavier vegetation. The soil is basically dry; and, without the water to flush minerals away, it is often alkaline and to some degree salty.
Soils range from sandy and rocky to clay. On hillsides, it can include the dreaded caliche, a sometimes impenetrable layer of calcium carbonate. Clay replaces grainier soils as one moves away from mountains, of which there are quite a few punctuating the landscape.
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" beloved in gardening nomenclature, but a thing to itself, requiring a sharp lookout as most plants -- even many cacti and aloes -- 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.
All of which is why the Sonoran Desert looks the way it does. Scrubby desert shrubs spaced sparsely across rocky or gravelly hillsides and plains. Thickets of little trees, leafless in the drought of sumer, but flourishing in the rains that flood across the land periodically. Sweeps of wildflowers that suddenly bloom, then dry and blow away on the ever-present wind. 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.
I love this place. I love the sheer brilliance of the daylight, with its flattened hues and clean-cut shadows. The way the earth changes from gold to gray to gold again with the passing of a single cloud. I love the sense that one can lean up against the sun -- it's so close here -- to get warm. And the clean feeling of desert soil.
And our unique pocket of it, the flat lands that constitute the drainage system of the Hassayampa River.
Of course, the Sonoran Desert contains many different regions within the larger ecosystem. There is even considerable variation across the city of Phoenix. Our immediate area is influenced by the proximitiy 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. 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 this garden, is proximity to more mountainous terrain This keeps our temperatures just 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! Temperatures peaked at 118 f (48 C) during the summer of 2016.
Quick mountain upthrusts are divided by the flattest of plains, built by soil that has washed or blown down from the slopes over the centuries. 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: mesquite, palo verde, fishhook cactus, cholla, desert poppy, globemallow, brittlebrush, saguaro, creosote, wolfberry...
It is intrinsically 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.
When we moved into the 2.5 ac property late in 2013, it conained a house, some small trees, and a smattering of little "landscape" plants along the front and west side. Everything else was nearly as bare as the moon, the inevitable weeds having presumeably been bulldozed when the house went on the market.
At first it was fascinating just to discover the wild plants, most of which were new to me. But one needs a garden, particularly in a land of bare earth! So during the first summer, I began to plan.
The rear of the house looks south and is edged from end to end with one of those glorious Arizona roofed patios that supply shade both for outdoor enjoyment and for protection from sun indoors. My regular trip out to the horse corrals was from the east end of this patio. So the decision was made to situate the garden along its east side. This would mean a fairly small area, squeezed in between patio and tack shed, but I was not about to start big. I knew that I knew next to nothing about gardening in the desert. Best to start small and see whether I could achieve anything with the conditions. So the first plants went in during early autumn of 2014. Muhlenbergia "Regal Mist" and Chrysactinia mexicana were the very first additions.
Since when, the garden has been a kaleidoscope of discovery.
The garden slopes downward to the east. In theory, this was to reduce the effect of the western sun and to allow cold winter air to flow away from the plantings. I think that on the whole this was correct, but I would modify both points from experience.
First, I would say the patio roof has proved the best protection from the afternoon sun. As I expand my plantings along the east wall of the house, the intensity of reflected light from the wall is creating more difficult conditions there.
Frost protection, in its turn, is dependant on just how low the temperatures go and for how long. For this location I think it best to rely primarily on plants that can sustain a few degrees of frost. Structural plants at least should have some leeway in the matter of cold, even if they must come back from the roots!
The other point to make about location has to do with wind. This is a factor specifc to this garden. Our property is located just on the edge of open desert, a wide, flat expanse with nothing to break the wind for many miles. And although we have a locally typical 6 ft concrete block wall around the property, its capacity as a windbreak is limited relative to the scale of the wind. Ironically, the garden is located at the end of a long patio complete with columns and roof, which form a fine wind tunnel. In the direction of the prevailing winds, of course!
So I have to bear in mind the effects of winds whipping down the garden. At their worst, they are the dessicating winds of June which have collected a good deal of heat from days of blowing across desert soil. Or the dust-laden windstorms that brown the air and leave grit in one's teeth and eyes. These winds suck moisture out of everything they bear down on. But there is some blow much of the year, so plants must have sturdy foliage not easily dehydrated. A windbreak on the west side of the property would be nice, but it would require extra water arrangements. And in the meantime the garden must survive on its own.
The question of water is a curious one here in a desert garden. We are actually under no direct restrictions as to water usage because our property is on a well. In an arrangement typical of the region, the well is shared among three homes and, in the absence of a meter, we split the bill equally. So my water restrictions are based on respect for the well itself and for the neighbors' bills (for the electricity used to pump the well). This in itself makes me water conscious, along with the awareness that the well must support three families plus perhaps eight horses and enough dogs to make a nice-sized pack! This is definitely an animal friendly neighborhood.
It makes sense to use drought-tolerant plants in any case, as they are likely to be best adapted to the requirements of the climate. At the same time, water and temporary shade are the only relief I can offer plants when temperatures soar above 110 F (43 C) with no relief for days on end. And I have found that plants that can accept water during the hottest periods are more likely to survive than plants that require completely dry summer conditions, unless they are fully adapted to desert heat. It is a curious trade-off, but it has limited the use of many otherwise desirable succulents, while encouraging me to experiment with plants from tropical climates, so long as they have some drought tolerance.
One rather humorous issue throughout the garden is the soil. It has become obvious that the dirt up by the patio is topsoil brought in when the house was built (2005). It is loose, sandy stuff with a bit of scree on top. About halfway down, the topsoil is still there, going down perhaps 1 foot or so, where it is replaced by native clay. By the time one reaches the bottom of the garden, the soil is only clay. It has the effect of providing for a full range of drainage needs, and I wish I had understood this fact when I began.
We read in various books how important it is to select plants from climates similar to our own. This way plants are more likely to succeed and to look appropriate in their settings. In the case of the desert garden, this is made more difficult by the fact that the plant resources of many desert regions have hardly been tapped, particularly for commercial production. Collectors have brought some gems into horticulture; but even so, there has been limited demand for ornamental garden plants in these regions, many of which have only recently -- if ever -- had significant human settlement. Some of the best plants I have are fairly recent introductions to the world of gardening.
Because of this paucity, it has been necessary to stretch the idea of similarity a bit. As things stand, I divide the really useful sources as follows: native desert, Australian, and Mediterranean, with occasional forays to the tropics and Africa.
Work in progress!!!