How are you irrigating trees?

[Daniel Kovach]

With apologies to those practicing in areas with greater precipitation, arid conditions and development codes generally preclude selecting trees that can survive with no additional water…  What materials and techniques are being used out there?  How are you handling different situations such as shrub planting, lawn, parking area planters, etc?

Thanks and Happy New Year!

[Doug Prouty]

For watering trees in the southwest region we are using drip irrigation with deep root watering tubes (see Rain Bird RWS tubes).  For shrubs in planting areas and in parking islands, it is typically point source drip irrigation as well (1 gallon per hour emission rate). For turf the norm is spray and rotor irrigation though a new item to the market for turf irrigation is subsurface in line drip tubing.  It hasn’t caught on yet but with watering restrictions it will be a popular option.

[Daniel Kovach]

Doug,

Thanks for the response.  I too have used RWS tubes; where do you locate them in relationship to the root ball and do you have any concerns about getting water to the actual root ball during plant establishment?

Do you arrange drip emitters on loops (circles) of drip tube around the tree?

[beijingreenspace]

As I’m sure you know location depends entirely on age, species and maturity of the tree, soil types etc.  there is no absolute rule.  I personally do not have confidence in the drip tubes without supplemental watering during the initial establishment period but obviously the more the watering cone is within the root zone the better.

I worked in Israel previously where rainfall is null and we depended entirely on irrigation. There the soil is very sandy (with loamy clay added to it) and we used a complex system of drippers for everything except the rare bits of lawn which had a carefully targeted array of sprayers and rotors.  We often just gave the trees a couple extra loops compared to shrubs with occasional deep watering when newly planted depending on need.

Several times we used the subsurface drip below lawns but it is challenging to maintain.  the lines are hard to flush, damage is hard to find, root preventative treatments must be done and we still needed an overhead system to wash in fertilizer or pest treatments.

I think it’s key to have each plant type on a different controlled zone so plant needs can be regulated based on evapotranspiration rates and actual plant needs.  It gets complex but you can do a lot with a little water with a properly zoned and maintained system.  Have never been able to go all in with any one brand though.  Rainbird had the best sprayers, Hunter the best rotors, Netafim the best drippers… at the time.  it’s a constantly evolving technology but one which we need to keep pushing.  

Now in China… don’t ask

[Les Ballard]

Some of the English country houses had exceptional owners – not to mention landscapers – and systems from the first own electricity lit home, to diverting rivers, to creating lakes and ice houses to get ice and store it for cooking/drinks, etc.  The overwhelming rule I think I may have discerned is, however much trouble you have to go to initially, make the system as labour-less as possible to run.  When someone tried to work out recently how the hanging gardens of babylon could have been watered they started from what may have been the wrong way round and calculating how many shadufs a day it would have needed to lift an appropriate amount of water from the river below.  (Shaduf = a counterpoise water lift system.)  I suppose it is like an illusion; you cannot believe the lady has been “levitated” by cramming a fork lift truck into the little area behind the stage curtains and that the noise is covered by the mysterious music.  

I guess that running water uphill and down a mountain, or an oil pipeline from Canada to Kansas, seems a lot of work but, in the end, it is labour and materials costs and actual will that are the main problems.  You certainly need, as John Wayne said in The Shootist, the will.  So do the clients and contractors, etc.  When that guy got the job of building the big dome in Venice and he did it with laying bricks in a herring-bone pattern, no-one knew how he was going to do it, maybe not him even, but done it was.  So some folk need faith as well as the will but, as they say, where there is a will, there is a way.

I am something of a tree nut and consistently tut to myself as I see things I would change yet, one way or another, most trees survive in areas when put there by folk who have done the job before.  Where they err most is in dealing with what they use most, namely mother nature, hence I have had folk fix trees broken in an ice storm with duct tape for the want of a shelter belt.  I have also advocated feathering tree plantations with bushes to keep the winds out, after thousands of big trees were layed down like wheat stalks, in what we incorrectly term corn circles, by small tornadoes in a storm getting under the canopy.  So it is good to have a list of options like grey water tanks, holed paving, irrigation systems, even gentlemens’ convenience run off filtered to the top of a membrane holding soil over sand before a soak away sink, but then we have our minds and they have no boundaries.  That I think is the final frontier we never reach; what we can think of next.         

[Serah Sibley]

Where are you located?

[Jason Bennink]

I prefer the subsurface irrigation(Netafim) that Doug referred to.  It’s expensive to install per square foot but you can’t beat the water efficiency. These systems need a pressure regulator(35-50psi) and filter post cylenoid.  Netafim stands out in subsurface irrigation because the emitters are self-flushing and clog resistant.  I like to put between one and three rings around each tree.  One ring per shrub or maybe run a line across them.    I’ve used Netafim alot in somewhat densely planted meandering xeriscapes with weed block. One technique that has worked well for me is to stake down the tubes on the drip emitter every three feet, so that I can track where the drips are being released by feeling through the weedblock.(emitters are 6″-18″ spaced so measure next emitter accordingly)  This way you can prep your area lay down irrigation, lay down weedblock, and plant directly on emitters in an organic yet targeted way.  

Release rates for emitters with Netafim range from .25 – .9 gpm.  Use lower gpm for clay soil, high for sandy soils and middle range for loam to get good moisture distribution.  One feed line generally runs over 100′ linear feet from water source single loaded in the regular size.  They just came out with a smaller diameter tubing that can be integrated with the larger stuff for feeding smaller lines cheaper and less intrusively.

I like the Hunter MP Rotators for water efficiency, although their claims on adjust-ability don’t seem very accurate.(Claims 8′-15′ but reductions in water pressure seem necessary to get below 10′ which subsequently cause the risers to drop- so it doesn’t pan out at any pressure)  These just don’t adjust down as far as they say for tight corners, don’t even try to use these on legs where there is a head with less than a 10′ radius, you cannot integrate with other sprayheads on account of their low gpm distribution being incompatible.  The Hunter PGP series are great for overhead broadcasting large areas on the cheap, but obviously much less efficient than the MP’s.  

[Jason Bennink]

 Installing a perforated pipe close to street trees can be fitted with a dripper for deeper penetration but also allow for aeration, fertilization, and simplify flood watering with a hose. Generally most important in clay soils.  

In sandy soils subsurface irrigation should be fine.

Also utilizing pavers instead of concrete within range of the prospective treeline, and grading to orient water into planted areas or over permeable hard-scape where water can be focused into useful areas.  I would love to build a system utilizing run-off gutters to supply a “french drain like” subsurface irrigation system to a large scale greenspace or grove.  

In Amsterdam there are trees that are several hundred years old which survive in heavily paved urban areas.  They have injection points(steel fittings coming out of the hard-scape placed strategically) utilized by a truck with a pressurized tank to inject nutrients, oxygen, and water.

[Daniel Kovach]

In an arid area (10″ annual) precipitation…  There are some riparian zones and the occasional shallow water table.

[Daniel Kovach]

…somewhat densely planted …xeriscapes … 

Interesting play on words, but I get what you mean.  Isn’t it interesting how the magnitude of water us is affected by the quantity of plant material.

 

Thanks all for the conversation; I’ve worked with most of these options at one time or another and pretty much agree with everyone.

[Tanya Olson]

I just finished a project in an arid high plains region – about the same precip as you are talking about. Trees and shrubs were selected to be either native or well adapted. The client did not want permanent irrigation (no one has it up there, except for farming, so could be a maintenance and installation problem).We specified Tree Gators for the trees and Tree Gator Jr. for the shrubs. These would be considered temporary irrigation until the plants get established. The planting is obviously minimal as these require hand-filling weekly but we also specify planting times to take as much advantage of seasonal precip as possible. Soils and plant selection always come first of course, but we’ve personally used the tree gators with good results.

[Daniel Kovach]

Tanya,  It’s great that you have a client willing to expend the effort necessary for proper maintenance of even sparse planting.  We run into situations where commercial project incorporates large site areas and the local governing authority mandates 90% coverage of plant material within three years.  We have very successful native plantings in the area with temporary or even no additional irrigation, but the situations described above generally demand a permaent irrigation system to get the growth rate needed to satisfy the code.

What were some of the plant material you used on the project you mentioned?

[Tanya Olson]

Plains cottonwood (the water table is within 6′ of the surface)  Rhus trilobata (Threeleaf Sumac), Chrysothamnus viscidiflorus (yellow rabbitbrush) and the usual suspects for shortgrass prairie native grasses – Little Bluestem, needlegrass, buffalo grass with some woody forbs like sages.

Like I indicated, planting numbers are in the 10’s, not 100’s….I went with what seemed like it would grow naturally in the area and what plants actually ARE growing in the area, so while the client may be willing to water for a summer or two, this was planned with the expectation of little to no maintenance…..Not succumbing to the fallicy of the zero maintenance landscape, just being realistic.

[Author]

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