No-mess shade tree for A/C unit?

sarabellJune 7, 2008

I'm looking for a tree to shade my A/C unit. Of course, I want something that won't make a mess in the unit-- a Cottonwood is off the table of course.

Other points I'd like:

-fairly strong

-bird / wildlife feature

-nice fall color

-I don't want it to get too huge

-pretty flowers /smell would be a plus, but not a dealbreaker. :)

Do maples have much mess? Or maybe a crabapple that will hold the fruits for the birds? How about redbuds?

Thanks in advance for any suggestions.

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ken_adrian Adrian MI cold Z5

i dont really understand why you need a 20 to 100 foot tree to cover a 3 foot square air conditioner????

if you want smell ... try a daphne ... max 3 to 4 feet ...

perhaps you should be looking for a small shrub rather than a tree ....


    Bookmark   June 7, 2008 at 4:30PM
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i thought ac units shouldn't be in the shade cause they work less efficiently then Am I wrong. Did you mean you want to 'disguise" it a bit?

    Bookmark   June 7, 2008 at 5:30PM
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I have always been told the a/c unit works better in the shade. Mine is in the sun most of the day, I can't plant anything to shade it though without it being too close to the house.

    Bookmark   June 7, 2008 at 5:59PM
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Quote= "I dont really understand why you need a 20 to 100 foot tree to cover a 3 foot square air conditioner????"

Wow, that's a lot of question marks.

I wouldn't want something 20-100 feet-- if you got that impression when I mentioned Cottonwoods, I only mentioned them as the obvious "NO" answer for their messiness. That's why I said I didn't want a huge tree, probably 20 ft or so. I don't think a shrub would offer it shade from the midday sun, unless the shrub had some sort of canopy. Am I missing something? (I do love daphne, though, but I don't think they'd thrive in my alkaline clay, sadly, for what that's worth).

Maybe I should have said that I've been reading ALL over that it helps the AC run much more energy efficiently if it is in shade. I'm not sure that a shrub would offer any shade except from early morning sun (the unit is in back, on the East side of my house, and in full sun until afternoon), & while eventually I may want to "disguise" the unit, right now I just want to help it run more efficiently if possible.

    Bookmark   June 7, 2008 at 6:49PM
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Glad for the correction of a misconception on acs. Actually, I'm sure it was my faulty memory and that it has been 8 months since we had ours on. This may be goofy and unacceptably unattractive, but could you put up a good looking retractable awning until you get the shade you want? I'm good at coming up with in-organic alternatives when I can't think of a plant answer.

    Bookmark   June 7, 2008 at 8:16PM
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Shading an outdoor AC/heatpump in summer will diminish the ambient temperature in the immediate area what, maybe 10 degrees, if that?
Actually, it won't make a bit of difference in the efficiency of your unit, since the unit is removing heat from inside your house and dissipating it to the outdoors.
If it were pulling in outdoor air and cooling it to circulate indoors, shading *might* provide a minimal improvement; but that's not the way they work.

Now, if you just want to hide/disguise the unit, that's another matter - but you'll need to choose plants that won't adversely impact air circulation around the unit, as well as plants that may be able to withstand the withering hot air exhausted as the fan blows over the coils to dissipate the therms removed from your living space.

    Bookmark   June 7, 2008 at 8:53PM
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idabean, great idea, thanks!

lucky_p- I haven't ran any large-scale studies personally or anything, but I've read quite a few publications disputing your take on this. I've read in a lot of places that shading the unit helps efficency-- it's frankly a place I might put a tree anyhow, so I'm not all that interested in a debate on it, honestly, anyway. :)

Maybe I'll start a new thread simply asking for small-ish trees that don't drop a lot of small 'litter.' lol Then we can skip the debate.

    Bookmark   June 7, 2008 at 9:12PM
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sarabell - I have a suggestion. Try not to get so defensive when people answer your questions. Most people who offer advice in this forum are motivated by a desire to help. Correcting their grammar and being sarcastic isn't going to get you much.

If you've spent time reading the posts here, you'd know that Ken always communicates with in an atypical manner. He is also knowledgeable, cares about people, and gives good advice.

lucky_p is another expert who gave you good advice. Ken and lucky_p know far more than I do so I'm glad when they respond when I have a question.

If your goal is to screen the A/C unit from view, you should probably use an appropriately sized evergreen. There are many small and moderately ized evergreens. I have a weeping yaupon holly that partially screens my AC and generator but they sit on a platform about 6' above ground so that's different from your situation. I don't think a yaupon holly would survive in your climate either.

Some people in this forum can advise you about what works in Nebraska. They are not likely to jump in after you have been defensive, critical, and correct writing styles. Put yourself in their shoes.

My two cents,

    Bookmark   June 7, 2008 at 10:16PM
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Arborvitae could provide some shade if positioned properly. Arbovitae have minimal problems as far as droping litter and roots.

    Bookmark   June 7, 2008 at 10:22PM
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I'm sorry- I'm not sure where I corrected grammar or was sarcastic, I must be coming off differently to you than I meant. On rereading, I can see a few parts of my responce where you might think I was sarcastic-- like my "what am I missing?" but I assure you that was sincere. lol There's probably something I'm missing there-- it's a real question.

I suppose I've been wordier and smilier with the people who are wordier and smilier-- I guess I figure if you post them, you want them, if not, you're more info-straight, and I'll be, too. :) Believe me, I wouldn't correct someone's grammar, as I'm no speller and feel no room to criticize anything in that rhelm.

Now I do feel a little defensive, :) b/c I didn't try to be offensive there at all. All of my responces have been sincere.

    Bookmark   June 7, 2008 at 11:26PM
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Noki- Thanks for the suggestion! I'll look into those.

Pam- I'm not yet real concerned with screening the A/C unit from view, I just want to shade the unit. Actually-- it's a place I'd like a tree anyway, and it will also end up shading the unit. So what I want is a tree that won't make a lot of mess to fall into an A/C unit-- I should have just asked the question that way, I seem to have inadvertantly made it confusing.

    Bookmark   June 7, 2008 at 11:32PM
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I took no offense. I'm certain that you have read things in print recommending shading the AC unit - but those folks don't know what they are talking about.
Will shade over an outdoor AC unit have a positive effect? Minimally - and probably not enough to make a noticeable improvement in your electric bill or indoor comfort.
Again, the way an air conditioner &/or air-to-air heatpump works is by removing therms(heat) from the air inside your home and dissipating them into the outdoor air by way of a fan blowing over the heat dissipation coils/fins in the unit. The shading of the unit by planting a tree would have so minimal an effect as to be literally worthless, from that perspective - though shading of your home from direct sun rays during the hottest part of the day will be a definite plus.
Placing the unit on the north side of the home would be a much better solution(why do the HVAC guys always locate them in the worst possible place?), as it would essentially be protected from direct sun at all times. Even better would be to install a ground-source heat pump, which is 2-3 times more energy-efficient than a traditional air-to-air heat pump - and 4-7 times more energy-efficient than the typical gas furnace.
Proper utilization of radiant barriers, cellulose or foam insulation, and caulking around doors, windows, sillplates, electrical outlets, etc., has the potential to cut heating/cooling costs by as much as 40-50%. We all need to be doing that!

Check out the online publication linked below, as well as its companion publication on Tree Placement

Here is a link that might be useful: Landscape Plantings for Energy Savings

    Bookmark   June 7, 2008 at 11:52PM
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lou_midlothian_tx(z8 DFW, Tx)

Look at shantung maple (acer truncatum). Very strong tree - rated one of best ice and wind resistant tree in Kansas so I assume it will work well for your location as well. It probably will grow to 25ft in your location. Very nice tree. Good fall color (yellow or orange-red of combination of both)

    Bookmark   June 8, 2008 at 10:55AM
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Lucky- you've convinced me. :) Nothing I've read has been in as good a detail as that, that's for sure.
Have you heard good things about heat pumps? We considered putting one in, but heard that they can't quite keep it cool on REALLY hot days. I'm sure you have more of those super-hot days than I do, so I'm curious.
Well, I do still want a tree in the location. lol (but I won't expect a big price break, I didn't really expect much there, but am trying to green up everything I can).

Lou- Sounds like a great option! I'll look into that one. Thanks!

    Bookmark   June 8, 2008 at 11:35AM
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I can tell you something I have seen rigged up, and it may sound crazy,lol. I know a guy who bought one of those mister systems (the kind you stand under to keep cool), and he clipped it onto the front of his unit. On really hot days he would turn the water on and let the mist cool his a/c unit. He swears that it helps, but I have no idea. Seems to me like all that water would cause rust though. I thought the whole idea was to make the unit last longer by keeping the compressor cooler, not really to make it more efficient.

    Bookmark   June 8, 2008 at 12:41PM
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Interesting setup, Alabama... Sounds a little more intense!

Thanks for all the input, guys.

    Bookmark   June 8, 2008 at 3:38PM
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quote="Check out the online publication linked below, as well as its companion publication on Tree Placement

Here is a link that might be useful: Landscape Plantings for Energy Savings"

Lucky-- now that I've had time to look at the link-- thanks! It's a great resource, and I'm finding it really helpful in my planning now.

    Bookmark   June 8, 2008 at 7:29PM
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There's a world of info on heat pumps, energy-efficiency, etc. on the 'net.
I'll start you out with three sites that will contain lots of info that you should read and digest. These will get you well on your way...

Doug Rye's website - - lots of info on how to make your home more energy-efficient and comfortable at the same time; info on geothermal heatpumps, cellulose insulation, radiant barriers, caulking, and proper home construction techniques.
Geothermal Consortium -

    Bookmark   June 8, 2008 at 10:01PM
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brandon7 TN_zone(7)

Below is a link to a site that will mathematically explain why shading (cooling) the outside unit of your AC can cut energy costs. In addition to these equations that describe how the ideal air conditioner would work, you must also take into consideration that, as the temperature difference (between inside and outside) increases, the efficiency of the air conditioner declines. This means even more energy is used when the outside unit is in a warmer environment.

Here is a link that might be useful: Thermodynamics of Air Conditioners

    Bookmark   June 9, 2008 at 9:41AM
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lou_midlothian_tx(z8 DFW, Tx)

I planted a shantung maple on the northwest side facing front of my house to shade A/C unit that is on the north side of the house for the very same reason - block out intense afternoon sun to keep the north part of the house cooler when the sun is far north enough to have effect on the north area. Granted, it may take 3-5 years for the tree to get large enough but it is a fast grower tree.

Planting shade trees in the right spots will have the largest impact on keeping the house cool but it takes forever. Buy an older house with large trees in the right spots so you don't have to suffer right away! That's what I plan on doing next time. I'm not getting any younger...

    Bookmark   June 9, 2008 at 10:19AM
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Thanks for all the info, guys!
I think I will go with the shantung maple this fall, after seeing some pictures and reading more. And if it doesn't help, & instread just looks beautiful, I can live with that. :)

    Bookmark   June 9, 2008 at 2:09PM
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lou_midlothian_tx(z8 DFW, Tx)

Sara -

If you want to wait till the winter to get 'Fire Dragon' for its intense red fall color (not typical for SM), check out sometime during the winter for info. They will only ship them in late winter before spring growth. It's about 50 dollars for 3-4 feet but they will grow fast when it gets enough water and fertilizer (organic fertilizer for me).

Here's the progression of mine...

Planted in Spring 2006... It was about 5 feet tall.

Beginning of Spring 2007...

In the middle of August... It has grown over 3 feet in 2007

In Feburary 2008 ...

In the middle of May 2008.. I had pruned off the bottom branches in the winter.

    Bookmark   June 9, 2008 at 7:30PM
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lou_midlothian_tx(z8 DFW, Tx)

This is last year during June 2007. New growth during the summer tend to be red...

That's what it looked like in the fall... Keep in mind, it probably happens because of my location and type of soil (pure caliche/limestone rubble soil). Yours may just turn brillant red, who knows but it will always be red of some sort.

    Bookmark   June 9, 2008 at 7:44PM
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Gorgeous, Lou! Thanks so much for posting the pictures. You've got a truly gorgeous tree!

I appreciate the link-- I was just realizing that my next step was to somehow find this in Omaha, Nebraska. lol

    Bookmark   June 9, 2008 at 11:07PM
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I don't have a digital pic of it right now but we actually DO utilize a mimosa tree RIGHT NOW to act as a very-manageable "shade umbrella" for over top of our Carrier outside air conditioner / heat pump unit.

I have ours planted about two feet away from the heat pump (NO kidding !) and I just occasionally prune the thing to 'steer' the foliage to grow above, and just 'in front of' the A/C unit, which is the side facing the sun.

The bi-pinnate leaves are not a big deal to clean up in the fall. The few that DO get into the A/C unit... I just blow out with a hand blower. Then with the leaves gone, there's nothing in the way to interfere with the 'heat pump' side of the units operations.

A fellow from a local heating and A/C co that we use took a pic of it last summer when he was here doing his annual checkup.
He said he'd give it to his boss, to maybe have posted in a heating & A/C trade magazine. But I never heard if it indeed was.

It's not especially great for fall color, but if you're looking for that "fine leaf" that gives a nice filtered shade WITHOUT blocking air flow (if pruned correctly, of course), then this is your tree.

You were also looking for "not too huge","flowers", and a "bird / wildlife feature" ?
Mimosas (Albizia julibrissin) have fuzzy little pink flowers that attract hummingbirds by the droves, once the tree matures a bit.
Some people...especially those in the about mimosa's tendency to be 'invasive' after a while, in that they start new trees in undesirable areas.
This may be true in warmer climes, but it simply ISN'T a problem in S. Ohio. My guess is that Nebraska would be similiar to Ohio in this way.

The only real concern for mimosas is cold- hardiness.
Lots of mimosas got killed out around here during the bad winters of '76 and '77 when the lows got to -25 F.

    Bookmark   June 13, 2008 at 1:32PM
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I bet you're right about climate similarities, ^ I do think Mimosa's are GORGEOUS. I hadn't considered them b/c it seemed like the little leaves would clog the system.
Ill look more into those to see if one's a good fit! Thanks for the input.

    Bookmark   June 14, 2008 at 4:30PM
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Mimosas will drop flower litter all over the ground. It would be a tree I would not plant near an AC unit because of that.
Mexican Plum or possible a fruiting pear or even Crepe Myrtle (rating?)make small trees to 25' that are fairly clean.
Both Eastern Red Cedar and the previously mentioned Arborvita would be small - medium size trees that seem very inoffensive even when planted to close to a building, however they are evergreen.

    Bookmark   June 16, 2008 at 11:19AM
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As a math guy I'd advise that no matter how technical someone sounds (including myself) if they can't disclose how they got their data (the numbers they are using), bounding cases (what makes this a maximum or minimum value) or their methodology (how they got to the answer they gave) . Then what you are reading is opinion. Now certainly not all opinions are equal and in many cases we can't collect or evaluate all the data required and so we rely on people with expertise. Often the way we judge this is by assuming that 'expert' is synonymous with 'professional'. That is, when I don't have any information about differentiating between plumbers I still generally call a plumber instead of a non-plumber (we are essentially assuming that market forces are at work here that keep the worst plumbers from working).

The problem with the internet, is that all bets are often off. Posts are made without attributing to research on the subject. People can claim to be experts but in a public forum there's no way to be sure and there's little in the way of economic incentive or accountability to help ensure give good advice. You might argue there's a 'social' payback but it's hard to say that such a system is 'as good' as a monetary one. Even websites we would assume to be reputable (like the Department of Energy) don't say how they got to their conclusions (incidentally they believe you can save up to 10% by shading your external A/C unit).

So without any kind of assurance of expertise you are really left with applying critical reasoning skills to the information you see. Let's take the alleged experts bounding case that shade can never make more than a 10 degree difference.

A simple unshaded thermometer can show a differential of 30 degrees on a sunny day. This is why we go to great lengths to control the impact of sunlight on weather stations. This is on an object that is very small so is not going to be absorbing much radiant energy. From that we're to believe that an object orders of magnitude larger, during the largest period of sunny days (summer is when we run these things), in direct sunlight (otherwise why would we be shading it?) can't ever rise more than 10 degrees above the ambient temp?

So it would appear that their estimate is wrong by up to a factor of three. On top of that I'd say that it's worth looking at what experts "don't say". For example wouldn't the amount of savings be influenced by the number of hours in the sun? So you would expect that any useful advice should be expressible as "You would need X hours of operation in direct sunlight to achieve Y watts of savings". Without that, then how do we know that the savings would be small? Not to mention the area we are trying to cool. A 1900sqft house and a 2900sqft house are, all other things being equal going to use different amounts of power. So what might be a negligible savings in one environment could be a useful savings in another.

Anyway, it's conceivable that the gains from shade are small but until someone expresses it either as a function of environmental variables or provides a proper bounding case then one persons opinion isn't demonstrably better than another.

    Bookmark   July 2, 2008 at 8:01AM
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mdvaden_of_oregon(NW Oregon)

I think there is something logical about AC units in the shade.

Whoever wrote earlier that it does not make a difference because the AC is just releasing heat, may want to do some research.

It's not just releasing, but it's releasing to air of a certain temperature. And it's very possible that an AC can release heat to cooler air better than warmer air.

One page that mentioned this was this:

I've barely begun to look this up, but will investigate further.

If it does make a difference, it would probably take a fairly big tree, because the fans blow so much air, they could displace much of the air beneath a tree in a matter of a few minutes.

Not really sure how much of a difference it will make, even if it does "technically" for but a short while.

Odds are, there's much more to gain by shading the building with trees, than the AC unit.

M. D. Vaden of Oregon

    Bookmark   July 2, 2008 at 11:58AM
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GROUND UP TO U: (vs. in-ground)
Since 1980: about 7,ooo btuh [separately in a ditch]
in damp clay as described below can be extracted from
52-deg earth with every 500 ft of 3/4" Poly-Black tubing
and circulated easily [up to 5-3/4" pipe runs with a header to 1.1/4"]
hdpe pipe 160 psi thicker sdr-9
on one
1) 1/6 hp (B&G pl 33)

if the loop is ~ 35 degrees (chilled) by/on (ARKANSAS)
a heat-pump, having ~ 18% methanol
antifreeze by volume ~20% glycol,
for usable(net) output per the following:
if at a depth of ~6-to-7ft, lower piping runs (back-in-bottom-of-ditch-tightly-packed)
x ditch length of 245 ft, up to 3-pipes in 2ft ditch
and on the bottom of the ditch,
up to 5 piping runs (2 ditches) on 1) pump 1/6hp
damp clay soil, and returns back in same ditch as follows:
RETURNS are on top at a depth of ~5ft (4.1/2 settles to 5ft in backfilling~) like a 'hair-pin over under design on side view...

each ditch may support a "2-TON" Hydro-Temp, which is equal to others' 2.2/2-"ton" rated units that use higher than normal blower speeds, or water:water with over pumping to just get "high" ratings... LOOK at COMPRESSOR labels:
they should have a 19,000-24,000 btuh compressor

Directly GeoLoops : ECL's (Earth Coupled Loops)
generally producing only ~ 4,200 btuh at 40-degrees/avg
and high volumes of ~ 3.1/2 gpm per 3/4"pipe
and no antifreeze keeping things obove 38-degrees
(ie @ 37 entering ECL, from loads applied/
with or without a heat pump... )

Please note: with antifreeze (38%)
ECL Ground-Loop Earth Coupled Loops
can circulate to a wide variety of
Pre-Heating of air or water

    Bookmark   July 2, 2008 at 1:13PM
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gtjon: can anyone draw a conclusion from your information, assuming they can understand the information? I can't.

    Bookmark   July 2, 2008 at 5:27PM
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Mimosas can indeed bloom up here in Ohio, but because of the much shorter growing season, they simply seem to not bloom with as much size, and certainly not as much 'INTENSITY'.... as they do in the South.

I can tell you for certain that in zone 6 they certainly don't freely SPREAD AROUND by themselves, and 'escape' out of the landscape into other areas, like they certainly do in Texas and other warmer climes.

In fact, up here, they NEED protection, up against a structure, ideally, to help keep wind off them during the coldest winter situations.

All ours are on the south side of various structures, very protected.
I always mulch our mimosas in the late fall with compost, and pull a great deal of the compost back in the spring...just in case we finally get a repeat of the dreadful winters of '76 and '77, when alot of people lost stuff like mimosa trees, and zoysia lawns, around the Midwest region.

And, honestly, the extremely fine bipinnately compound mimosa leaflets are absoluely NO PROBLEM blowing...or 'hosing' out of the heat pump / AC fins.

Over the last couple of years I've trained myself to be pretty much of a pro... at 'steering' the growth of new mimosa shading branches with correct pruning by using my Felco #2s.
There's not a lot of margin for error, when the mimosa's planted only 33" from the house, and 20" from the A/C unit !

( ;

    Bookmark   July 7, 2008 at 2:36PM
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