Drip Irrigation

I would definitely agree with Joe that lower sustainable water use for residential gardens is very much about "right plant for the right place", but would still suggest that drip irrigation is inherently more efficient in the application of such water without the run-off, wind-drift and evaporation one can't help but get with spray irrigation.  I would really like to see the support for the statement that a well designed conventional spray system still uses less water than drip, as quite frankly, I don't believe this statement is universal, nor even the norm.  All of the gardens I showed typically only get 15 to 30 minutes of irrigation via drip emitters 2 to 3 times a week in the hottest weather, and in combination with a good regularly reapplied mulch 2 to 3 inches thick, most all the plants have been fine with this amount of watering.  In a sandy soil garden in the western half of San Francisco, built upon old dunes, I would typically only water for 10 minutes maximum with microspray/drip, and again program for 2 to 3 times a week.  Admittedly, I garden and design gardens in the cooler maritime mediterranean climate of the inner SF Bay Area, where it doesn't get all that hot.  This allows me to use non-drought tolerant plants in such situations as well, but I will typically link them to their own independent valve which may get irrigation set daily for just 5 to 10 minutes during the hottest weather.  The fact that these valves are drip, with lower pressures and limited volume of water does mean that they are using significantly less water than a spray system would for the same plantings.  I have had the opportunity to comparison test similar plantings side by side between spray systems and drip in the same garden, and have nearly always found that the drip irrigated plants establish faster, more often look better under hotter weather conditions, and there are no problems with wind drift and water run-off, as well as less weeds.  I wouldn't ever consider a spray system to be a better design for narrow parkway strips between street and sidewalk, it is inherently more wasteful of water and more subject to wind drift.  I recently replaced such spray heads in a street strip only 3.0 feet wide in nearby Alameda, with buried 1/4 in-line drip tubing on 12 inch centers.  No more run-off, and  9 mpnths later the plantings of Dymondia, Echeveria imbricata, Aeonium nobile, Coleonema 'Sunset Gold', Cotyledon orbiculata, Lavandula 'Hidcote' and Sedum 'Angelina' have completely filled in and are thriving with just twice a week 25 minute water cycles in a sandy loam soil of dredged bay fill.  The lawn that was originally in this strip had never looked green even with 3 times a week watering from pop-up spray heads, and always had some water runoff into the street.

As to how to counteract wildlife that have bothered drip irrigation, I have only really had problems with the occasional squirrels, deer have not been a problem in any of my gardens where they have free range, but then you may be able to see from my preferred planting styles that I don't typically leave much bare earth showing, nor exposed drip lines.  I haven't had any problems with raccoons tearing up drip irigation, either, although they have been terribly destructive of some of my favorite plants(bromeliads), in the past, before I elected to cover vulnerable plantings with bird netting, which ended the problem.  With the squirrels, as I already mentioned, I had to get more clever about mounting the hard plastic misters in trees, so that it would take them hanging upside down to be able to gnaw on the emitters.  Squirrels never have shown any interest in the polyethylene supply tubing, nor have gophers or moles, in my personal experience.

I would have to suggest that tubing and emitters would need to be shallow buried and mulch covered in gardens where animals have been a problem, but if even this doesn't work, then utilizing a drip system that relies on microspray emitters within popup risers, and hard plumbed with pvc pipe runs rather than flexible poly tubing would still be a way around this, and possibly locating inground drip emitters within protective wire baskets, as used to protect root balls from rodents.  If you have to go to the trouble of installing buried pvc pipe for irrigation, it may make more sense to install spray heads that utilize lower volume stream sprays, but also need to run for longer periods because they apply substantially less water.  In garden situations where I have used such a system, I still find it uses more water and plants grow more slowly than with a comparable drip system, and much more care needs to be taken to ensure that full irrigation coverage is not eventually blocked by plant growth.

The point about drip tubing heating up significantly in hot summer areas makes the case for shallow burying the lines, and/or keeping the garden well mulched so that the lines aren't exposed.  As a general principle, I prefer the mechanics of the garden to remain invisible anyway, and don't like to leave any drip tubing exposed long term if at all possible.  In fact, for patio applications, I typically will use 1/4 diameter copper tubing which can more easily be painted to match the house for supply lines, and always prefer to run drip tubing up through the drain holes of pots rather than over the rims, if it is a new installation and not a retrofit.

In fact, I find myself returning to planting design themes first explored in the drought years of the mid 1970's, when I was still a landscape architecture student and all pumped up on designing gardens with predominantly California native plants and no permanent supplemental irrigation. If push came to shove, and we are faced with a similar drought situation as places like Adelaide, Australia are going through, I am sure that I could adapt my garden designs to be even more drought tolerant, but we aren't faced with the same degree of limited water(yet!).   I still found it more personally rewarding to combine a few plants from outside California to add to the mix, yet would fit within the same once a month supplemental irrigation schedule for a mid-peninsula Menlo Park garden.  Over 30 years later, this garden has still held up, and matured nicely.  These days I am more inclined to include more colorful South African, Australian or Mexican plants into the mix,(especially succulents), as I am after using plants for the overall feeling and effects they bring to the garden, rather than trying to imitate some natural landscape.  I particularly enjoy matching a plant to the situation at hand, and harmonizing plants from similar climates from around the world into one setting, as an attempt to define a Bay Area look that fits our growing and climatic conditions, yet doesn't need to read as "dormant" or "resting" at the height of summer.  Perhaps this represents a "less evolved" approach to landscape design in a time of limited water resources and disappearing native plants due to habitat loss, and certainly does not reflect the more politically correct approach of no summer irrigation and only growing what is locally native, but I prefer my contact with such environments out in the surrounding hills and bayside, rather than my own garden.

The bottom line is one of making the best use of resources in a sustainable manner that also pleases the end user, and if it also pleases the designer, this is a bonus...  We will be faced with the need to elimate wasteful irrigated lawns, even when they are allegedly drought tolerant ones such as the tall fescue blends.  I won't design around a tall fescue lawn anymore unless the client absolutley insists; instead, I've been pushing using no water Kikuyu lawns,(so far no takers), artificial turf(2 installed so far), and several lawns using non irrigated Carex species such as Carex tumulicola(as in the photo of the garden with the recycled concrete slab bench), and Carex pansa and Carex praegacilis lawns.  Even better in my view is ripping out the lawn all together and replacing with shrubs/ground covers and succulents, or providing decomposed granite as the blank space play area if one is needed for young kids at home.

While I admire gardeners who actually design gardens with no irrigation required at all, I find that the plantings possible in such a regimen are usually a bit limiting.  Trying to achieve the goal of less water use has pushed me toward much more garden installation and planting in late fall and winter, and only confirms that such wet season plantings almost always establish better with less water required the following summer than a spring planted garden.  It does become a problem however when dealing with clay soils and lots of rain for days on end, and the danger of creating compacted soil that hardens into concrete once dried out.  I also find myself using a lot more desert climate plants that absolutely need no summer irrigation to survive, and that includes many non-desert plants such as Puyas, Dyckias, Hechtias that have the desert look, yet still are colorful and vibrant and even bloom in the height of summer.   

--- On Mon, 7/20/09, Joseph Seals <thegardenguru@yahoo.com> wrote:

From: Joseph Seals <thegardenguru@yahoo.com>
Subject: RE: Watering in Summer
To: "'mediterranean climate gardening e-mail forum for gardeners in these climates throughout the world'" <medit-plants@ucdavis.edu>, mikemace@att.net
Date: Monday, July 20, 2009, 6:58 PM

Please don't take this as a personal afront Michael but you do make me realize that a lot of people -- including, possibly, other members of this forum -- have the idea that it's an either/or situation:
 
Either we use drip or we waste/use a lot of water with traditional irrigation systems.
 
That's not the case.
 
I think I've made it clear that the essential key to water conservation is "right plant, right place".  In other words, using plants ("Mediterranean") that don't need much supplemental water.
 
After that, it's a matter of using an "effective" watering system that trains plants to have an extensive root system -- one that is what we call "drought tolerant".
 
I know many people believe an old myth that says "plant roots find water".  I'm sure plant roots don't.  Plant roots have no sensing organs, no radar, no brain to lead them to wet soil. 
 
Plant roots go where the water is -- where the gardener puts it.  If we water deeply and infrequently and just beyond the drip line, we train roots to go deep and wide.  And that's what gives them the abililty to hold up when the rainless season comes along or when the rainy seasons come along dry. 
 
My experience -- and that of my students and clients and associates -- is that using water wisely/effectively in the beginning leads to unthirsty plants in the long run.  I've done the numbers and in the long run, watering effectively with appropriate new versions of traditonal irrigation uses less total water than with drip.
 
 
And thanks to David F. for giving me (and all others) the opportunity to understand his irrigation approach and sytem better.
 
I should quit now otherwise I'll be accused of going from "tirade" to "obsessed". ;-)
 
Joe
 


Joe Seals
Horticultural Consultant
Pismo Beach, California
Home/Office: 805-295-6039

--- On Tue, 7/21/09, Michael Mace <mikemace@att.net> wrote:

From: Michael Mace <mikemace@att.net>
Subject: RE: Watering in Summer
To: "'mediterranean climate gardening e-mail forum for gardeners in these climates throughout the world'" <medit-plants@ucdavis.edu>
Date: Tuesday, July 21, 2009, 1:16 AM

I've been pretty happy with my drip system, but then I have an acre of land
and couldn't afford to water it any other way.

Regarding the timing issue, if those drip tubes are above ground, you need
to give them time to cool off after they've been in the sun.  Watering in
the afternoon will give your plants a nice little dose of scalding water,
and because the tubes get soft when warm, you'll have more cases of joints
blowing apart.

Mike
San Jose, CA (zone 9, min temp 20F)


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