Cake is good, but so are trees. Photo courtesy of Flickr user Son of Groucho.
Today’s blog post title is a play on the old saying “you can’t have your cake and eat it too.” In other words, once you’ve eaten the cake, you don’t have it anymore. Likewise, if you have a tree, you’ll need to use a lot of water which might run afoul of water restrictions. Or will it? Today’s post demonstrates that you can have healthy trees AND save water at the same time.
May 2019. The camphor (and the lawn) is relatively healthy before three years of drought. Photo courtesy of Google Maps
A few weeks ago I got an email from ISA-certified arborist and blog reader Curtis Short, who wanted to share his success with rejuvenating a prized landscape tree that had become severely stressed as a result of residential water restrictions. The tree is camphor (Cinnamomum camphora), which grows well in warmer parts of the country (USDA hardiness zones 9b-11b). This particular tree is about 40 years old and the showpiece of a residential landscape in the Oakmont neighborhood of Santa Rosa, CA.
March 2022. Nearly all the leaves on the camphor have become chlorotic after three droughty years and lack of irrigation since the previous spring. Photo by Curtis Short.
In March 2022 Curtis received an email from the homeowner (a retired meteorologist) who was concerned about the declining health of the camphor after irrigation was discontinued in mid-2021. Prior to this, the sprinklers were run daily during the dry months to support the tree as well as the surrounding lawn. The lawn, with its shallow but dense root system, recovers quickly with seasonal rains. The damage to the tree’s root system, however, has led to leaf senescence and drop.
Two other arborists had given the tree a thumbs down: one said it needed to be removed and the other said that even if the tree recovered it would never regain its original form. Curtis chose a different approach, suggesting that the homeowner could resuscitate the tree by: *removing competition (the lawn) for water and nutrients, *refining the irrigation system, *applying nitrogen to stimulate new leaf growth, and *supplying an arborist chip mulch to the landscape.
May 2022. Tree resuscitation efforts began in March, as chlorotic leaves continue to drop. Photo by Curtis Short.
In April the homeowner applied glyphosate to kill the lawn, removed the old lawn sprinkler system, and replaced it with a 100-foot drip irrigation system near the canopy dripline and outwards where most of the tree’s fine roots are located. (For those who are curious, the system consisted of 12-inch spaced Techline emitters with a 0.9 gallon per hour dispersal rate.) Next, a layer of arborist wood chips were applied to at least a 4” depth. In May, ten pounds of ammonium sulfate (a great source of nitrogen) were applied on top of the chips and watered in.
June 2022. Tree recovery begins along with a new irrigation regime. Photo by Curtis Short.
The homeowner’s irrigation plan departed dramatically from the original daily watering routine. Being a retired meteorologist, the homeowner was naturally interested in collecting data. The original two lawn stations each put out 45 gallons per day, for a total lawn water usage of 630 gallons per week. With the new drip irrigation system, irrigation was limited to one 35 minute application per week, with a total weekly water use of 105 gallons.
July 2022. The tree canopy has markely improved in color and density with new leaf growth. Photo by Curtis Short.
Curtis photographed the tree’s recovery as a way to reassure the homeowners that the tree was neither dead nor disfigured. The homeowners are now aware that trees cannot go “cold turkey” in efforts to reduce irrigation water use. Locating the drip system beneath the mulch layer means evaporation is reduced and that the mulch layer stays hydrated, supporting its population of mycorrhizae and other beneficial microbes.
September 2022. In August, a second application of 10 pounds of ammonium sulfate was applied and watered in. Photo by Curtis Short.
I appreciated Curtis sending me this case study as we all face the likelihood of hotter temperatures and possible water restrictions. Reduction of water-hungry ground covers, judicious use of water, and a living layer of arborist wood chips are key to helping our landscapes survive.
May 2023. A little more than a year after resuscitation efforts began, the dark green tree canopy is full and healthy. Bare branches have all but disappeared, and the tree’s health is arguably better than it was in 2019 before the three-year drought period. Photo by Curtis Short.
While we can’t ever
control or even predict the weather, in most places it is important to have a
plan on how to deliver water to our home gardens during the hot, dry months of
the summer. Aside from reducing water
need through some good management practices, delivering water in an efficient
and sustainable way is important when planning and planting our home
gardens.
When there is
scarcity, it is necessary to conserve. Several years I got to see scarcity in
person on a sustainable agriculture tour of New Mexico. Farmers in New Mexico have only limited
access to water from irrigation canals, to flood irrigate their fields, or even
wells for drip irrigation.
This severe lack of
water got me thinking about how much we take water for granted in our own
gardens. We often apply as much as we
want or need in an inefficient manner (using sprinklers, sprayers, etc.)
because we think it will always be there when we turn on the tap.
Where I’m located in
Nebraska we are also blessed to have water falling from the sky. Sometimes
there’s too much, and at others there’s not enough. But that’s much better than
in some places – I visited some parts of New Mexico on a farm tour where they
get seven inches of rainfall in a normal year. Seven. Total.
Thinking about
conserving what water we have means that we are good stewards and are ready for
when issues do arise. And let’s face it, there are some times in the summer
that are dry where water conservation will help reduce using water, which can
also save money.
When we talk about
conserving water, there are two ways to go about it. First, look for ways to
reduce the need for water. Then, look at ways to reduce water waste and usage
whenever you need to use water on your lawn, landscape or garden.
Reducing the need for
water
During dry times, it
can be necessary to provide water to the garden to keep it growing healthfully
along. However, there are many ways to reduce water loss or increase the amount
that stays in the soil around the plants.
Mulching not only
reduces weeds, but also helps hold moisture in the soil. Having one to two
inches of mulch on landscape beds can reduce evaporation from the soil and
decrease the amount of water you need. Newly planted trees should be mulched
for the first few years to help hold moisture in the root zone as well.
Mulching is also important in the vegetable garden. Using straw or shredded newspaper are simple ways to conserve moisture, beat weeds and even reduce diseases. Note that this is shredded newspaper used on top of the soil for a mulch, not whole sheets applied below another mulch or on top of the ground. That process is called “sheet mulching” and we typically don’t recommend it here at the GPs because it limits air movement into the soil and can disrupt the soil microbiome. Stick only to shredded newspaper as a top dressing. (See the bottom of the article for journal articles discussing paper and straw mulches).
Shredded newspaper in my tomato bed. There are 2ft woodchip mulch walkways between 4ft wide beds.
You can use woodchip
mulch in the vegetable garden, but it can be difficult to manage when you are
frequently planting, replanting, or harvesting crops. If you accidentally incorporate it into the
soil, it can tie up nitrogen available to plants and cause deficiencies. As long as you are good at keeping it on the
surface, it isn’t as much of an issue.
Large scale gardens or
farms make use of black plastic as mulches to do much the same thing. Plastic mulches
are typically beyond the scale needed for home vegetable gardens and have their
own set of drawbacks such as limiting water and air movement, but for those struggling
with difficult weeds or with issues limiting manual removal (disability,
limited movement, etc) it may be explored for smaller scale production. There
are now even biodegradable plastic and paper mulches available. Use of these
does require drip irrigation beneath the mulch, as rain cannot penetrate to the
root zone. With the issues associated with them, plastic mulches would be
considered a last resort for all but the largest home vegetable gardens, and
many of my GP colleagues recommend against them for all home garden situations –
but they can have their very limited place in the home garden toolbox. And we definitely recommend against the use
of plastics and landscape fabrics in ornamental beds and landscapes.
Choose plants that
require less water. There are many plants available that have lower water
requirements. Ornamental grasses, Liatris (blazing star), Kniphofia (red hot
poker) and sunflowers come to mind. Most native plants are commonly thought to
have lower water requirements, but this isn’t always the case and natives may
not thrive in altered ecosystems (urban settings or even managed landscapes).
Most bulbs also are water efficient and do not require extra watering, as are
most culinary herbs.
Mowing less often in
the hot and dry summer also can conserve water if you are one who waters the
lawn. I’m not a big fan of watering lawns, since it is such a large water usage,
but I know there are those who prefer to have their lawns lush and green at all
times. Instead, when the summer gets hot and dry, leaving the grass on the
taller side can help it stay green even without water. Many of the grasses we
grow here are cool-season and go semi-dormant in the heat. Stopping mowing when
the heat starts slows down growth and the need for water.
Irrigating Efficiently
with Drip
When it comes to
getting water to the garden, there are definitely more efficient ways to make
it happen.
Unfortunately, the
most common method — using sprinklers — is also the least efficient. It is hard
to direct the water to the right place, and during periods of high heat
evaporation takes up much more water than you think. But there are ways to get
water to your thirsty plants without running up the water bill.
Drip irrigation is probably
amongst the most efficient and sustainable ways to water your landscape or
vegetable garden. This method allows you to apply water directly to plants in a
controlled manner, rather than spraying an entire area with water. Also, since the water is applied directly to
the ground rather than sprayed through the hot summer air, the water is much
less likely to evaporate.
Drip irrigation tubing. Each drip opening emits on this version emits 1 gallon of water per hour.
There are a few
different types of drip irrigation systems available. Probably the easiest to install is a drip
tape system. This is a deflated tape
that already has water-emitting slits cut into it. While each slit applies a precise amount of
water over a given time period, the pre-determined regular placement of the
slits makes this system better for plants grown in rows, like vegetables,
rather than landscapes where plants are of differing sizes and spacing. And while it can be used for vegetable gardens,
probably the easiest system for a landscape would be one where there are tubes
you can cut to various lengths and insert controlled drip emitters at
customized locations. Another use for
this type of drip irrigation could be for containers on a porch or deck – you
can easily run the tubing out of sight along a bannister or railing and direct
individual emitters to individual containers.
It all sounds
complicated, and larger systems can be, but there are small and simple kits you
can easily find at many garden centers or online retailers available for home
gardeners to install their own within a matter of hours. You will need to have
some skill at reading directions to install them, but the process is pretty
simple.
For information on
setting up drip irrigation for your home garden, check out these great
resources from Extension institutions across the country:
Soaker hoses are a
similar concept to drip irrigation, but instead of small drips these hoses just
emit water all along the hose. Still better than sprinklers, these hoses are
quite a bit less efficient than drip, since you can’t direct the water exactly
where you want it. They are also easy to
apply too-much water to an area since they can emit large volumes. Installation
is pretty simple, though, since you just lay the hose down where you want it.
One great benefit of both drip irrigation and soaker hoses is the application of automation. Using a timer can make it easy to keep the garden watered through the season. Timers can be as simple as a dial to manually run the irrigation for a specified time or fully automatic to run the irrigation for various lengths of time on different days of the week. Some more advanced timers also have rain sensors or soil probes to reduce or avoid running when rain makes watering unnecessary (if you don’t have a sensor, remember to stop automatic running until the soil has dried). And in today’s emerging technology, there are also timers or flow controls that can be automated or controlled from a phone app. The timer that I’m now using at home connects to my Wi-fi, and in addition to allowing me to control and observe the watering status from anywhere in the world, connects to local weather data to automatically set a “smart watering” schedule taking into account rainfall, temperature, wind speed, and other factors.
My fancy water timer.
Another effective way
of providing water to your garden is through water catchment. Water catchment is just a fancy way of saying
that you use a rain barrel. Here you are collecting rain runoff to use in place
of water from the tap. There are some ultra-low-flow drip irrigation systems
that you can use with rain barrels (if they are raised high enough to get water
pressure), but this use is usually for watering by hand. For larger gardens,
the large IBC totes that hold 200 or more gallons can make good water catchment
barrels. Just make sure that if you are
using them (or any other barrel) for fruit or vegetable production that they
are made of food-safe plastic and their previous contents were also food safe. (Check out our guide on Building a Rain Barrel)
