“There is a large number of vineyards in the Valley, their total extent being between 2,000 and 3,000 acres. They are largely localized in the vicinity of Burbank and in the Sunland region, with small acreages elsewhere. Grapes usually are grown without irrigation in this area and are nearly always located on rather sandy, gravelly, or stony soils that are hardly capable of producing any other fruit without irrigation. Table, raisin, and wine varieties are grown, but the wine grapes predominate. . . Peaches are an important crop in the southeastern part of the area . . . They are grown for the most part on soils of sand, sandy loam, or fine sandy loam texture, both with and without irrigation. Some of the very sandy soils retain water remarkably well, considering their texture, and give very good results with this fruit even without irrigation. . . Apricots, like the peaches, are grown both with and without irrigation.”
The above excerpt is from a soil survey of the San Fernando Valley — including crops grown in each soil type — that was conducted in 1917. I found this account fascinating for several reasons; first, that significant acreage of peach and apricot trees were once planted in the Valley despite the fact that you hardly ever see a fruit bearing peach tree nowadays and only occasionally an apricot; second, the fact that some of this acreage did not receive any irrigation – – who knew apricots and peaches could thrive in the Valley without any water other than winter rain?; third, that upwards of 3,000 acres of grapevines were “usually grown without irrigation” in porous, inferior quality soil. It’s a lesson on the toughness of peaches, apricots and, especially, grapes. The entire 72 page survey is available via the Internet, at no charge, and is accessible by entering “San Fernando Valley soil survey (1917)” into your computer’s search box.
In fact, it appears that nearly all fruit bearing trees and vines are remarkably thrifty when it comes to water use and the thirstiest among them, once mature, should not require more than a single monthly soaking in this part of the world between spring and fall. Exceptions would be fig trees which, although they are native to the Mediterranean, have shallow roots and may require twice a month soaking in hot weather and avocado trees, which may also benefit from two monthly soakings. Having said that, I have seen mature avocado trees that were watered minimally, if at all, during the summer. Weather and soil conditions, as well as the presence or absence of mulch, can make significant differences when it comes to irrigation frequency of fruit trees.
The above investigation was prompted by an e-mail from Rich Vargas. “Do you have any idea of the history of the Valley as far as soil composition goes?” he asked. “I am in North Hollywood by Vineland and Victory and the soil around here is a grey sand that seems absolutely devoid of any nutrients. When you pour water on it, it’s water phobic, meaning the water will bead up and run off. If left untreated with organic material, you can run water for a while and yet if you were to scrape away the first inch of soil you would be stunned to see it’s completely dry below! Is this just from decades of inattention and pounding heat?”
The type of soil you describe, based on the history of soil formation in your area, is the result of alluvial deposits, meaning soil particles that were transported and settled there as a result of overflow from rivers (including the Los Angles River) and streams. Such soil is redeemable, as you indicate, through addition of compost or other organic material. You are accurate in implicating “pounding heat” as an accessory to the “water phobic” quality of your soil. Pounding heat on unprotected ground is devastating to the micro-organisms that live in a healthy soil and make it fertile by their decomposition of minerals and organic matter. That’s why, for example, it’s a good idea even if you have no plans yet for your bare front yard to cover the ground with mulch and water it down occasionally, until you decide what to do with the area. This will protect the soil and provide organic matter and moisture for soil sustaining micro-organisms that will benefit future plantings.
I stumbled upon alfalfa the other day spilling over a block wall. I don’t know how in the world it got there since it’s not normally seen in urban areas. It’s a most attractive plant, in addition to being a staple in the diet of dairy cows and other livestock. Alfalfa is suitable plant to grow in a bare yard until you decide what to do with it. Just scatter alfalfa seed over the ground and cover it with a quarter inch of compost or just plain dirt. It will give you a nice pasture with purple flowers that attract bees and all sorts of beneficial insects. Then, when you are ready to plant fruit trees, vegetables, or a garden of ornamentals, just hoe the afalfa into the ground where it will benefit your plantings in its capacity as a nitrogen-rich green manure.
Tip of the Week: There is a new website that provides information on plants native to your corner of California. The site is a joint effort between the California Native Plant Society and the Jepson Herbarium at UC Berkeley. When you reach the site at calscape.org, you will find a long search box after the words “Plants Native To.” Enter your address into the box, and you will immediately see a plethora of native species — there are over 600 species native to my own mid-Valley address, for example — divided into 15 categories. Just studying the categories will teach you something about natives. For instance, of the 600 + species suitable for my address, some 400 are in the “drought tolerant” category. Being a California native does not automatically confer drought tolerance. More than 200 of the species I can grow are in the “partial shade” category, demonstrating that a large proportion of California natives are not sun-loving, and 140 are “riparian” or somewhat thirsty species. Finally, nearly 70 of the species native to my address are in the “very easy” category, meaning they can be grown without fear that they will suddenly die as long as they are given standard garden care. Click on any photo for a detailed description of that species, including a large selection of companion plants for landscape design purposes.