Re: MGS/ Ran Pauker lecture in Berkeley

--- "Sean A. O'Hara" <sean.ohara@groupmail.com> wrote:
> Folks in No. Calif. -
> 
> Just a reminder that there is a Mediterranean Garden
> Society meeting this 
> Saturday at 1:30pm, at the Regional Parks Botanical
> Garden in Tilden Park, 
> Berkeley.  Our featured speaker is Ran Pauker, who
> will talk about his work 
> as Director of the Water-Wise Gardening Facility,
> Kibbutz Nir Oz, 
> Israel.  Could be interesting!  Also, it would be a
> great opportunity to 
> get acquainted (or re-acquainted) with this
> wonderful garden of California 
> Native Plants. 

For those who missed the meeting, the lecture was
really quite informative as to the specifics of
growing drought tolerant plants under limited watering
conditions!  One of the main points that Ran brought
up, and which is seldom applied in California gardens,
is the concept of widely spacing plants to give each a
volume of soil without competition from other plants. 
He says that this can make the difference for plants
without supplemental irrigation, especially in drought
years.  The concept of retaining drainage water from
roofs, roads, air conditioners and directing to
plantings which need supplemental water to survive
through the year, is also a concept that is not often
practiced here.

It was amazing to me to hear that turf grasses could
be maintained in 40C temps in summer with only monthly
irrigation.  I wonder if the 2 foot depth of sand as
planting medium over their loamy sand soils really
makes all the difference?  Ran mentioned that rooting
depths for turf were typically 1.5 meters/5 foot.  I
think that our clay soils here in Berkeley work
against such rooting depths, because they inhibit
oxygen exchange, and have a much slower water
penetration to these depths.  All I do know, is that
my small lawn is also in shade under trees as at Ran's
kibbutz, is much cooler in summer, yet will not stay
green and lush on only monthly irrigation, while many
other plants in my garden, under identical conditions,
such as succulents and bromeliads are perfectly
content with monthly watering.

The idea of rain shadows under evergreen trees, and
the impacts of this was also something we don't think
much about here in California.  Ran measured up to
20mm/1"  less rain reaching the ground for each rain
shower below evergreen trees in winter, and found this
much less so below deciduous trees.  It is interesting
to note that several evergreen trees here in Northern
California tend to catch and increase precipitation
below them.  Coast redwoods and Eucalyptus globulus
both will collect fog drip and create "rain" at ground
level when they are in a foggy windy area.  The
vegetation below redwoods is much more lush because of
this, while Blue Gums tend to inhibit any but the
toughest plants from growing within their accumulation
of debris.  Senecio milkanoides and Toyon/Heteromeles
arbutifolia are two plants which can compete with Blue
Gums locally here in the Bay Area.

Ran also stressed that the choice of mulch can steal
water away from plants.  Bark mulch 3 inches thick can
create a "wetting tax", the first 20mm of
rain/irrigation must wet the mulch before soaking
through to the soil.  If soil and mulch are dried out
between showers, this can result in significant
reduction in water available to plants, as accumulated
over the rainy season, especially if each shower is
not that much.  In many cases at the Kibbutz, using
shallowly cultivated sandy laom as the only mulch made
 more water available throughout the dry season than
mulching...  Reading between the lines, if you are
using summer spray irrigation over thick mulches, and
allow them to dry out before the next irrigation, up
to the first inch of water may never reach the
plants...  This is something I have seen first hand; a
garden mulched with 5 inches/125mm of coarse bark
mulch was absolutely bone dry below the mulch, even
with 20 minutes of spray irrigation 3 times a week. 
And the owners were perplexed why the garden was so
dry looking!!  Changing the mulch to a 3 inch layer of
fine textured bark/small scoria(red lava) and chicken
manure mix allowed the plants to thrive on a third of
this water.

One last tidbit of info; Ran measured the "rain tax"
below an Italian Cypress/Cuppressus sempervirens as
being 100% of the 350mm/12 inches of rain over a 6
week period.  If you have been wondering why you can't
get much to grow adjacent your Italian Cypress, keep
this in mind! On the other hand, if you are growing
things which must keep dry in our wet mediterranean
winters, move those plants to the base of this tree
each winter! 

In summary,Ran made several good points about
designing for situations where you aren't able to give
extra water beyond rainfall, such as; spacing water
loving plants more widely apart, banking rain by
holding and redirecting it, and closer fit between a
plant's water needs and your local climate's
evapotranspiration rates.  These all make sense,  as
we encounter diminishing water availability in fast
growing areas such as California.  This look can also
be beautiful, and the natural vegetation in the
Sonoran Desert of Arizona and Baja California is a
perfect example, but would be a sea change in most
people's planting styles here in coastal California.

I wish there were more people writing about what
actually survives in their areas on rainfall alone, as
this may become more and more important in the future.
 Ran Pauker had a very nice study of just such plants
under 30 years of observation, and it was interesting
to  hear his results.  One last thing, the Negev
Desert at Kibbutz Nir-Oz doesn't sound nearly as
difficult to garden in as Riyadh, Saudi Arabia, where
even Prosopis/Mesquite must receive some supplemental
irrigation to survive, and Schinus molle can't survive
the summer heat once it gets up above 120F/50C for
several months.  I found myself imagining that this
kibbutz location was similar to San Felipe, Baja
California on the Sea of Cortez with respect to
climate, although Nir Oz may get more winter rain at
250mm/10 inches average.         

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