Sustainable
gardening in Southern California means coping with highly variable
precipitation. This month, we’re continuing to manage the effects of an epic
four-year drought. And now scientists
are cautiously predicting an El Niño winter, with higher than average amounts
of rainfall. Yup, that’s gardening in
our capricious mediterranean climate!
The
U.S. Weather Service has official precipitation records for the L.A. Civic
Center going back to the 1877-78 season (the water year runs
from July 1-June 30) [1]. Since then, the average yearly rainfall is 14.93 inches [1, 2]. During the 138 year period, extreme
precipitation years (both high and low) have become more common.
The
graph above shows the number of years below and above the average for two
25-year periods: 1890-1915 and 1990-2015.
One thing is clear: there are more ‘extreme precipitation’ years (both
below and above average) in the current period. The last 25 years had 10 years with a deficit
of at least 5 inches. This compares to 6
such years in the earlier period. But
there were also 6 years with 5 or more inches over the average (compared to two
from 1890-1915). So we need to prepare not
only for more ‘drought’ years, but also for more ‘wet’ ones.
First,
a word of caution. Mother Nature’s Backyard is situated in the flat lowlands of
the Los Angeles Basin. Our advice is
most applicable to gardeners in similar areas. If you live in the foothills, and
particularly if you live along a creek, in areas below recent burns, or those
prone to landslides, you may need to take additional precautions. Consult your local municipality for advice on
preparing for an El Niño winter. Recent
ocean temperatures indicate that this may be a very wet winter. Prepare now if you live in a flood-prone
area!
The
rest of us still have several months to make our gardens both more water-wise and
more El Niño proof. Some of the
suggestions below may not be applicable.
But we hope you’ll adapt some for use in your garden – and get moving on
making them happen. The time is now to prepare for the winter rains.
1.
Consider decreasing the area covered
with impervious materials.
Traditional walkways, driveways, concrete or mortared patios all are impervious
surfaces. Water runs off them and, very often, into the storm drains and out to
the ocean. That’s one reason why urban
areas like the Los Angeles basin need such extensive storm drain systems.
El Niño years can be tricky. Whether they bring deluges or persistent showers,
excess water can become a challenge for local gardens. Fortunately, you can take several steps to
prevent/decrease the effects of running or standing water in your garden.
One strategy is to increase the percentage
of the yard that can infiltrate rain water.
This allows more water to infiltrate in place, rather than aggregate in
ponds or rivulets. We discuss several infiltration
options below (see suggestions 2 & 3).
Another idea is to simply convert impermeable surfaces to permeable
ones. This helps control excess rain water
and also increases the amount of irrigation water available to plants (by
decreasing summer run-off).
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| Permeable walkways in Mother Nature's Backyard |
There are many ways to make walkways,
patios and driveways more permeable (see the links below). Some, like replacing your driveway with
permeable paving materials, require more time, skill and money. Others, like converting an old concrete patio
or walkway into something more pervious, can be done quite economically, if
you’re able to do most of the work yourself.
For ideas on permeable surfaces see:
2.
Use the rainwater that falls on your
roof. Your roof is a large rain collector. Does the water
from your roof end up in the storm drains?
Does it make a muddy mess around your house, threatening the health of
your foundation? If so, now is the time to install gutters and harvest rain
from your roof.
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| A rain chain is another way to direct water from a gutter |
3.
Infiltrate more water into the
ground using a rain garden, dry well or dry swale. Water from impermeable surfaces must
go somewhere. In the past, most of it has ended up in the ocean. But each year, more California gardeners are installing
simple infiltration ‘devices’ in their gardens.
While getting rid of one problem
(excess runoff), these devices also solve another: providing deep water
resources for trees and shrubs. They allow
water to infiltrate into the ground, replenishing the ground water. Trees, shrubs and other long-rooted plants
can then access this ground water well into summer.
If you have an area where rain water
puddles, you may want to consider a simple infiltration device like a dry
well. These take little space, are
relatively easy to install, and often solve the puddling issue admirably. They can be used in unplanted areas, making
them a good option for patios and utility areas covered in gravel mulch. See the links below for more information.
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| Rain garden - Mother Nature's Backyard garden |
Rain gardens and infiltration swales
are the perfect complement to rain gutters, infiltrating the water from a roof.
While no two rain gardens or dry swales are the same, they all slow or store
water briefly, allowing it to percolate into the ground. They
can be planted or not; they can be disguised as a natural-looking dry creek. Some
are used as seating or play areas in the dry season. And they allow you to use plants that like a
little extra winter water, even if the rest of your garden is quite
water-wise.
Rain gardens, dry wells and dry
(infiltration) swales are easy to incorporate when you are installing a new
garden (or re-doing an old one). Like
all hardscape features, they’re easiest to install before a garden is
planted. If you’re removing your lawn,
now is a good time to consider whether a dry well, rain garden or dry swale is
right for your garden. Here are some good resources:
4.
Consider storing some water. People in dry climates around the world store
rainwater for use in dry periods. The
regulations on rain water collection/storage are changing, so check your local
municipality to learn what is legal.
Nearly all S. California municipalities permit you to store water in
rain barrels, to be used for watering your garden (not for drinking).
As
water becomes more scarce (and costly) it’s silly to not take full advantage of
the rain that falls on your property. California law is now clear – you own
that water! Don’t let it slip
away. Act now to use your clean, free
rain water this winter.
5.
Use the ‘high’ and ‘low’ spots in
the garden to best advantage. Sandy soils dry out quickly in
summer; clay soils tend to hold water, creating wet spots in winter. Most gardens have areas that are ‘high and
dry’ and others that are low and moist.
If not, it’s relatively easy to create a bit of garden topography with
low berms (artful mounds) and shallow swales.
Whether your soil drains quickly,
slowly, or somewhere in between, creating modest garden topography has several
advantages. First, a planted berm is
often an excellent way screen short, unsightly views (for example to block
views of parked vehicles). Berms and
swales can also be used to direct and infiltrate rain water. And they add interest to a flat garden.
Another benefit of berms and swales
is that they allow you to grow plants with water requirements slightly
different from those available in the rest of your garden. For example, plants that hate wet feet can be
grown at the top of a berm (driest place). Plants that like a little extra
water often do well at the bottom of a slope or swale. For more on creating garden topography see: http://mother-natures-backyard.blogspot.com/2012/12/getting-to-know-your-gardens-soil.html.
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| Fresh organic mulch: Garden of Dreams, CSU Dominguez Hills |
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| Fall pruning - Mother Nature's Backyard garden |
8.
Choose trees, shrubs and vines that
can take both drought and excess rain. Global climate change makes planning for the future a
bit more challenging. We’re already
seeing some effects: hotter temperatures overall; more temperature and
precipitation extremes; changes in the timing of the seasons. The recent drought is just a taste of things
to come.
Trees, vines and large shrubs are an
excellent way to provide shade. In fact, all local gardeners should be planting
now for future shade. With planning and
proper care, large shade plants can live for many years. But choosing
the best adapted plants is something we’re just beginning to grapple with.
In Southern California, our best
choices will need to withstand both the periodic droughts and periods of
greater precipitation. Only certain plants are so adapted. California native
trees and shrubs are better candidates than those from the tropics or other
regions with plenty of precipitation.
But what native trees and shrubs will be able to take both the heat and
the precipitation extremes? We have some
ideas and will discuss that topic next month (September, 2015).
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| Planting Mother Nature's Backyard garden |
9.
Take advantage of winter rains for
planting. Winter is the easiest time to plant in
lowland Southern California. Soils are
well-moistened and the temperatures cooler. That’s why California native gardens are
traditionally planted in late fall or winter.
Winter is not only the easiest time
to plant, but it’s also the best for plant health. California native plants are adapted to our
seasonal weather patterns. Many are
dormant (or at least slow growing) by late summer or fall; they are primed to
grow with the winter/spring rains. Plant
them in late fall/winter and they will establish themselves right on
schedule.
But plant California native plants
in summer and they’ll be ‘seasonally confused’; the heat says ‘it’s time to go
dormant’ while the irrigation water says ‘it’s time to grow’. In fact, summer planting is difficult not only
for the plants, but also for the gardener. Planting with the rains is yet another example
of working with Mother Nature. Gardening elders have learned – often through
painful experience - that working with
Mother Nature is better than trying to work against
her!
An El Niño year can be an excellent
opportunity to start a new garden – or plant trees and large shrubs. So do your summer planning now. Figure out what plants you need. Plan to buy required plants at the fall plant
sales, and plant them with the winter rains.
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| Rainy day - Mother Nature's Backyard garden |
10.
Enjoy today’s weather, whatever it
may be. The news on climate change can be downright
depressing. The best antidote is to sit
in your garden. Enjoy the hot, dry days
of late summer. Watch the abundant life
that enlivens California gardens this time of year. Enjoy the balmy evenings – and vow to plant more
silvery-colored shrubs to enhance your twilight garden.
Look forward to the cool rains. Sit out in your covered patio and smell the
rain. Listen to the sounds of a rainy
day in your garden. Watch the birds and
other creatures – what are they doing on a rainy day? Put your potted plants out to benefit from
the good, pure water.
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- http://www.laalmanac.com/weather/we13.htm
- http://www.wunderground.com/blog/weatherhistorian/show.html
