Last
month we discussed several topics related to developing a water management plan:
determining your water goals, creating a Water Zone plan and managing/harvesting
precipitation water. If you’re just joining the ‘Designing
Your Colorado-friendly Garden’ series, we suggest starting at the
beginning (https://mothernaturesmontrosegarden.blogspot.com/p/creating-your-colorado-friendly-garden.html)
and working forward. The monthly activities will help you design an
attractive, functional, sustainable garden you’ll enjoy for years to come.
Introduction and Background
By
this point you’ve probably guessed that the ‘irrigation system’ in a Colorado-friendly Garden is not likely
to be a conventional, one size fits all ‘sprinkler system’. Instead it will be tailored to the Water Zone
Plan, site characteristics and the needs of the gardeners themselves. Part of the trick to designing a functional and enjoyable garden is to look
honestly at your own needs and constraints.
Proper
watering of native (and other) plants is at least as important as selecting the
right plant for a given water zone.
More native plants die in home gardens due to improper watering than
almost any other cause. An irrigation
system that allows you to water plants easily and properly is key to a
successful garden. And because your
garden will mature – and climate will change – your irrigation system must also
be flexible.
Your
‘irrigation system’ can be anything from a simple spigot and hose to a complex
automated irrigation system (or some combination of both). There’s no one system that’s right for all
gardens. If your landscape plan includes
more than one Water Zone – or if your site is anything other than a small flat
piece of ground – you may need to use several types of irrigation methods to
water everything properly. Fortunately,
you have several options to choose from – and plenty of resources to turn to
for advice.
We
summarize the benefits, limitations and best uses for the most common types of
irrigation methods used in Western gardens at: http://www.slideshare.net/cvadheim/irrigation-methods-for-southern-california-gardens This table reflects our experience with
watering native plants in Southern California as well as Western Colorado; other
experts may present other points of view.
Realize that the relative advantages and disadvantages vary with climate,
soil and other factors. Much of the
readily available information on watering Colorado native plants – both on-line
and in books - is directed to gardeners on the Front Range, the eastern plains or
in desert areas. While generally useful,
remember that such information is not specific to our unique climate(s) in western
Colorado.
Planning an Irrigation System: Example
from 112 Willow St.
It’s
easier to plan your own irrigation system once you’ve seen a worked example. So, let’s design a new irrigation system for
112 Willow Street, an example of a small Western suburban garden. We will present an example of a larger
garden, Mother Nature’s Montrose Garden, next month.
The
current irrigation system for 112 Willow Street is shown on the site map
(above). The ‘system’ may be similar to your own. It consists of two separate water lines: one
line that supplies conventional sprinklers (front and back) and a second supplying
4 hose bibs (spigots). The sprinklers
are controlled by two timers: one for the front yard and one for the back. The backyard timer has two stations: the
northern part of the backyard (nearest the house; station 1) and the rest
(station 2).
As
discussed before (July, 2020), the front yard will be left as is for now; the
automated sprinkler system will continue to water this area every 10 days for
the near future. However, in considering
the irrigation needs of the entire yard, we realize that an additional spigot
at the east side of the front yard would greatly facilitate watering the ‘meditation
garden’. We add this to the Irrigation
System Map, even though the installation may take place several years in the
future.
The
backyard sprinkler system won’t need a lot of modification to make it suitable
for irrigating the new lawn (see above).
One sprinkler head is superfluous and another would be better if moved
slightly. That and some new, water
efficient sprinkler heads with the correct spray radius (8-10 ft) and we’re in
business. The sprinkler system will likely provide all
the water needed for the ‘shady seating’ area as well. If not, we can supplement occasionally with a
hose and sprinkler. If you need more
information on irrigation systems and their design we highly recommend the
following tutorials: http://www.irrigationtutorials.com/
.
Planning
an irrigation system for the vegetable garden requires deciding how the space
will actually be used. The gardeners
like raised beds, and there’s room for at least two different configurations,
each providing 120-130 square feet of growing space (see below). The gardeners will consider how to arrange the
raised beds and will design them in October (2020). Whatever the configuration, they’ll want an irrigation
system that’s flexible and as water-wise as possible.
The
gardeners decide to use inexpensive ooze-type soaker hoses, covered with mulch,
to water the raised vegetable beds. This
will allow them to water only the planted areas, leaving the pathways dry. Installing a hose bib for each bed will give
the most flexibility. The soaker hoses can be attached directly to the hose bib
in each bed. And each bed can be controlled separately, providing the right
amount of water for each crop through the growing season.
During
most of the year, the gardeners will control the water manually, as needed.
This is, in fact, the most water-efficient method of irrigation. But what about during the three week summer
vacation when the gardeners are routinely away?
Depending
on how we design the irrigation system, we can have all the beds on a single,
multi-station timer or use individual, battery operated timers for each bed. In our experience, many smaller yards,
particularly if landscaped with water-wise plants, don’t require sophisticated
(and costly) irrigation systems with sensors.
Inexpensive hose timers are readily available, easy to use and work well
in many situations. You can even store
them away when they aren’t needed to extend their life. For more advice on timers and sensors see:
The
‘butterfly garden’ area, which is on a 6-9% slope, has presented an irrigation
challenge in the past. The gardeners
plan to install primarily water-wise plants – and place the most drought-tolerant
of these on the drier top of the slope. This will go a long way towards making the
area less problematic. But even though the plants will be Water Zone
2 at maturity, the ‘butterfly garden’ will require summer water during the
establishment phase (likely the first year or two after planting) and
occasionally thereafter. The gardeners will need an irrigation method that is
flexible; and once again, they have several options.
One
possibility is to use drip irrigation for the first few years. While some native plant nurseries recommend against drip irrigation, in fact this
method can be useful in some circumstances in our part of Colorado. Drip irrigation has come a long way in the
past decade. For a good, thorough tutorial on drip irrigation see http://www.dripirrigation.com/drip_tutorial.php
. There are many more choices of
emitters including micro-sprinklers and soaker-emitters. These can be used successfully with Colorado
native plants under certain conditions. In our experience, drip irrigation is best
used to get plants started or for container plants.
There
are several downsides to drip irrigation. Drip systems can be costly, particularly if
you pay to have them installed. The emitters can plug – or even pop off –
during irrigation, so gardeners should inspect their emitters regularly for
proper functioning. Don’t assume your
plants are being watered adequately unless you check your drip system
routinely!!
As
the root systems grow, the emitters need to be relocated to provide optimal
water to the plants. Remember that the root systems of many native plants
expand quickly; failure to move emitters around growing plants is another
common mistake made by home gardeners.
In
our experience, simple soaker hoses can also be used on small garden slopes,
provided that drainage is adequate and watering is done over several days. The secret is to water the area, using a slow
seep rate, until runoff starts. After a
few times you’ll know just how long this takes. Then water again in the next day or two. This will provide a good soaking, and can be
repeated every other week, or as needed, during the first summer. The advantages of soaker hoses over drip are
several: 1) lower cost; 2) lower maintenance requirements; 3) more even water
coverage (good as plant roots grow out); 4) if covered with mulch they last for
years, providing for supplemental water when needed.
Because
the top of the slope dries out before the bottom, the gardeners will use
several soaker hoses to give them maximal flexibility. The soaker hoses will be installed once the
‘butterfly garden’ is planted to insure good coverage. After securing the hoses with landscaping
staples (also called ‘landscape fabric pins’ or ‘sod staples’), they will be
covered with mulch. They will be connected
to the nearby hose bib (spigot) with a hose when in use. When not in use they will be completely
invisible.
The
gardeners could also choose to water the ‘butterfly garden’ with a sprinkler
that attaches to a hose. There are many
options available – including ones that are quite attractive. This option has the advantage of being very
flexible; you can just water the dry areas and not worry about areas that don’t
need water. It also provides a good approximation of rain
if you need to water during winter/spring dry spells.
But
any type of overhead watering, whether with conventional sprinklers or those
attached to a hose, has several disadvantages.
First, overhead irrigation is less water efficient: in dry climates like
ours, some water will evaporate before reaching the ground and more will
evaporate from the mulch without reaching the ground beneath. The other disadvantage, particularly for
summer watering, is that overhead watering increases the chance of fungal
diseases. Wet leaves and warm conditions
favor the growth of fungi; and leaf splash can spread fungal spores from one
plant to the next.
As
currently envisioned, the ‘meditation area’ will not need much irrigation once
established and the gardeners plan to use stored rainwater to supply some of
the water in the future. The irrigation
system for this area will depend on the landscape design for this area. The back of the neighbor’s garage abuts this
area – an ‘ugly view’. The arrangement
of the seating – and choice of plants – will dictate the irrigation needs for
this area. If the homeowners choose a
trellis and vine to mask the ‘ugly view’ they will need to supply irrigation to
the vines. Native honeysuckle vines
would do well and require only occasional water once established. We’ll have to wait to finish the irrigation
system for the ‘meditation area’.
On
further review of the ‘near final’ irrigation plan for 112 Willow, the
gardeners decide that having a spigot to water the meditation garden will be a
necessity as soon as that area is installed.
The idea of watering the area from a backyard spigot doesn’t seem
workable.
Designing Your
Irrigation Plan
We
suggest the following steps in designing your irrigation system:
- Using a copy of Site Map 2, map
your existing irrigation system
- Compare your current system with
your Water Zone map.
- Decide what parts of your current
irrigation system are compatible with the Water Zones in your new
garden. You may be surprised;
conventional sprinkler systems can sometimes be modified to work. If parts of the system are no longer
needed, they can be capped off. And new sprinkler heads can decrease water
loss to evaporation.
- Consider how you’ll supply water
to Water Zones 1 and 2. Remember
that new plants will need to be watered for at least one or two summers
until they are established – and Zone 2 and 3 plants will need occasional
summer water thereafter.
Once
you’ve decided on possible irrigation choices, we suggest that you step back
and evaluate. In fact, you may want to
put your plans aside for a day or two.
Then ask yourself the following questions:
·
Are
these choices consistent with the amount of time/effort you want to spend
watering the landscape?
·
Are
they feasible in terms of cost, skills needed to construct, maintenance
requirements?
·
Look
at your Base Map 2; are you sure you haven’t located irrigation lines where
they will interfere with anything critical (like gas & electric
lines).
·
Is
the ‘system’ flexible (for example, can you change if the initial method doesn’t
work well; can you use overlapping systems if you need to water one part of a
Zone a bit more)?
·
Have
you planned enough: spigots? Sprinkler
heads? controllers? Are these in convenient locations? If
not, now is the time to do something about it.
Once
you’re happy with your plan then construct a final Irrigation Plan map. Be sure to note location of spigots, location
of irrigation pipes, sprinkler risers (if any), pop-up irrigation heads (and
the types of heads), and location of drip irrigation lines and soaker hoses (if
any).
Additional Internet
Resources
https://cmg.extension.colostate.edu/gardening-resources/online-garden-publications/water-wise-landscaping-xeriscaping/
https://coloradowaterwise.org/Resources-and-References
Xeriscape Colorado: The Complete Guide.
CL Ellefson and D Winger. 2004, Westcliffe Publishers, Englewood CO.
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We welcome your comments (below). You can also send your questions to: monaturesmontrosegarden@gmail.com
