Re: Watering in Summer

While I find several points Joe states that make sense, I find the "tirade" against drip irrigation a bit too general in the points it makes to hold water.  We in the SF Bay Area do not have the issue of hard water to deal with; our water comes from the high Sierras and has very little salt content, so salt accumulation in the soils is not a big issue here for gardeneners.  Secondly, drip irrigation can be designed utilizing in-line emitter that can be placed closely or widely, and used as an alternative to to spray irrigation, yet achieve equal coverage to spray, without the waste of water to wind and sun.  I find such systems especially useful on steeper slopes where I prefer slower applications of water to avoid runoff, and usually time such systems to run for 15 to 20 minutes at a time, and repeat several times during the same day, to get water deeper without runoff.  The results speak for themselves, especially when dealing with steep slopes of
 heavy clay, the plantings grow better with less water used, and no erosion runoff or wasted water.

Secondarily, spray irrigation encourages more weed growth, as water is applied everywhere, rather than just at the plants root zones.  I do use drip irrigation with micro sprays or misters where I have plantings that root as they spread, mostly to wet a wider root zone than an emitter can do, and with less hand labor to install more closely spaced 1/4 inch in-line emitter line, which can also be used to the same purpose.

I know that there are also people who swear by daily spray irrigation for sort 10 minute cycles to keep the root zone moist, and feel that this uses less water.  It may in fact make sense when gardening with mostly water loving plants in hotter inland climates, that are so densely planted or have constantly changing plantings that would mitigate against a more permanent drip irrigation system.

I especially appreciate drip systems with micro-spray heads or misters for the ease with which they can be added to apply targeted water to more water loving plants within a predominantly dry loving succulent or mediterranean plantings garden.  The fact that the drip lines can be left on the surface and shallow buried or just covered with mulch makes them easier to install, and I often route multiple lines for different drip valves through the same area to be able to accomodate the varied water needs of the plants.  As I do like to combine subtropicals and even bromeliads into otherwise drought tolerant garden designs, the flexibility of drip irrigation greatly facilitates this, while not overwatering plants that don't need or appreciate the water.

I think many people resist drip irrigation simply because they feel it is less reliable, more maintenance intensive, or simply because they like to visibly see what is getting watered to ensure themselves that watering is being done.  I learned this all too well the one time I had specified an underground netafim drip irrigation system for a new subdivision in Livermore, and the homeowners would overwater the lawns because they didn't trust the programmed run times recommended and set for them prior to turning over the home landscaping to the new buyer.  When you leave such systems in the control of a homeowner rather than a landscape maintenance crew who knows how the system works, the results can negate all the potential water savings of such an underground system.  Ever since, I have only used above ground spray stystems for lawns, period...

As to whether it is best to water at any one time of day over another, it will really vary with your local microclimate, amount and timing of winds, type of plants being irrigated, etc.  For many California native plants there do not seem to be issues with wet/warm soils in summer, but others are particularly sensitive and need caution with any summer watering to keep them healthy, with Fremontodendrons being a prime example.

I tend more towards programming automatic irrigation for early morning applications, myself, mostly because the water pressure is usually highest before people get up in the morning, and local winds are usually at their calmest at this time.  For the more tropical/subtropical plants that I also employ,(especially bromeliads), I like to supplement with a brief afternoon wet down around 1 pm or so, for just a few minutes daily, to give them a bit of humidity that they prefer to look their best.  This allows me to combine glowing foliage color of hybrid Neoregelias or Billbergias with succulents such as Graptoveria 'Fred Ives' or Aeonium canariense v. subplanum and Sedum palmeri, without overwatering the succulents.  The brief burst of mist uses barely any water at all, and I usually link this with drip irrigation of pots, which might also get 2 or 3 applications of a couple of minutes of irrigation at the height of summer.  Most drought tolerant container
 plants seem to thrive on this under my cool summer conditions; using little actual water while always presenting as lush and happy.  Other terrestrial bromeliads that I also like to combine with drought tolerant plantings in gardens need no such additional irrigation, such as Dyckias and Puyas, or hardier Aechmea species such as A. distichantha.  I like combining these things because they grow so well in a Mediterranean climate, need little additional water, yet give summer seasonal interest to the garden as well.  I can appreciate the fact that the base norm for a native plant garden in summer is dormancy, and like the look in nature, but find it rather boring visually in most native plant residential gardens.

I realize that this approach is not all that popular with the "all natives/no summer irrigation" crowd, but it still speaks to the possibilities of rational use of irrigation for summer gardens, and is another form of designing gardens for Mediterranean climate gardens.  I find that even the Medit Plant Journal seems to feature a lot of gardens that don't quite walk the walk; what with lawns, subtropicals, watered containers as part of the whole garden look.  If one is truly committed to no water summer gardens, it would seem that utilizing desert adapted species is another viable approach to creating no-water Mediterranean climate gardens, and is also an approach that I enjoy using to get more summer interest plantings with color/form/texture that needs little water. 

--- On Sun, 7/19/09, Joseph Seals <thegardenguru@yahoo.com> wrote:

> From: Joseph Seals <thegardenguru@yahoo.com>
> Subject: Watering in Summer
> To: "Plant Forum Mediterranean" <medit-plants@ucdavis.edu>
> Date: Sunday, July 19, 2009, 12:26 PM
> I
> think the window for watering is 4am to 9am.  That
> gives the garden plenty of time for surface water to
> evaporate by evening so that the plants don't go into
> the night in a situation of high humidity.  With most
> plants and most foliar diseases, the critical factor that
> causes foliar diseases is not "free water" on the
> foliage.  The environmental factors are cool, moist
> nights and warm dry days (much as what we have here on the
> Central Coast!).
>  
> I've never seen any good studies that showed cool,
> moist soil in summer was better than hot, moist soil for
> root development.  But given that most Mediterranean
> climate plants do most of their root growth from late winter
> into spring and then essentially rest during the summer, it
> could be that those "temporary" water-temnperature
> situations in summerhave some effect on the roots.
>  
> With that said, there's a lot more to be said --
> as others have already said.
>  
> First, a good "Mediterranean" garden should
> need little to no water in summer.  (Yes, I know, this
> has been a serious subject of another recent thread.)
>  
> Second, something I've found that works very well
> during the hottest part of summer when some plants
> are flagging and I know I shouldn't put water to
> the soil is to spray the plants or turn on the
> overheads.  Because it's so hot and/or windy,
> the plants dry out before evening.  This works for
> every Medit. plant I've used it on with no ill
> effects.  And no, water on leaves doesn't
> "burn" the plant (an old myth).  The real
> benefit is that I've not watered the soil and hence
> encouraged the complex of root rots (Phytophthora as well as
> Pythium, Rhizoctonia and more).
>  
> Third, the factors that lead to root rot are many and
> complicated.  It's not just that the soil
> is "moist and warm".  It also includes the
> fact that a saturated soil -- one that is wet from frequent
> waterings -- lacks oxygen and the root rot organisms thrive
> in such anaerobic conditions.  Most importantly, an
> anaerobic soil discourages (outright kills in most cases)
> the beneficial organisms of a soil, particularly mycorrhizal
> fungi -- the really good guys that are key in the survival
> and optimal growth of natives (in their native land). In the
> summertime, our mycorrhizal fungi go dormant and are not
> prepared for water, hence they themselves
> "rot".  Mycorrhizal fungi offer many benefits
> including that they actively keep detrimental fungi in
> check.
>  
> Another factor in root rot development is an
> accumulation of salt in the soil.  Much of California
> has hard water (it's INCREDIBLY HARD here and almost as
> hard in Southern California).  Most root rot organisms
> thrive on higher salt levels.  And, as a seque to my
> final point, salt levels in gardens have increased
> tremednously over the last couple of decades with the rising
> popularity of drip systems.
>  
> Fourth, drip systems (not that you asked, Pamela) are
> an efficient way to use water (as engineers would testify)
> but not close to being the most effective way to water
> plants to encourage them to become more drought tolerant in
> our climates.
>  
> Too many people have bought into the concept of
> Micro-Irrigation and there's too much money behind it so
> I don't suspect that it will be questioned too much nor
> too soon.  But there are many inherent problems with
> it. I won't go into the cosmetic issues nor a host of
> minor issues but the four big issues are that drip
> systems don't water in a way that encourages a plant to
> have a wide and deep root system, drip systems leave a soil
> saturated for too long,  drip systems concentrate salts
> and, fourth, drip systems don't push oxygen into a soil
> as do typical sprinkler and other, more
> "effective" systems.
>  
> Micro-irrigation -- including "drip" -- was
> invented in Israel to make use of little available water
> that offered a low-pressure situation.  It was
> created for row crops and some fruit trees.  It
> was not designed for a drought-tolerant landscape.
>  
> Joe
> 
> 
> Joe Seals 
> Horticultural
> Consultant 
> Pismo Beach, California 
> Home/Office: 805-295-6039
>  
> Pamela Steele
> wrote:
>  
> What are Mediterranean climate
> gardeners' views on the time of day to
> water plants.  We need to water our new plants
> here in Spain for their first year over the dormancy period
> in our hot dry summer until they get their roots
> down.  I was always led to believe the
> best time for these new plants to get most benefit was
> watering in the evening and so the ground would
> stay damp all night until morning.  Lately, I have
> had some interesting discussions  about
> watering in the evening and there are some theories
> that it is not as beneficial to the plants as early
> morning (7-8am) watering because in the evening the ground
> is still hot from the baking sun. 
>  
> Watering in the early
> morning  when the ground is relatively cold is
> apparently more beneficial for the
> roots.  Do you agree?
>  
> I would love to hear your
> experience and advice.  
> Best wishes
> Pamela 
> 
> 
> 
> 
>
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