STOP! And don't strike a match. If you have either natural gas or propane/Lp gas,have the system leak tested immediately. If you have neither,call "dig-tess" to see if a public line crosses your property. With that out of the way,we can talk about your odor.

It could be an aging sewer pipe. Plant roots can find cracks in the pipe grow into it and make it larger, allowing sewer gases and other crap to escape through and into the soil. It could also be a gas leak.

In my experience, both as a homeowner and firefighter, gas smells do not change much with temperature, but it would be better to call your gas utility to do a check anyway.
If you have a septic system that may be a problem to look into after the gas leak is ruled out.
Find out what the problem is before doing more to attempt to mask it.

"In my experience, both as a homeowner and firefighter, gas smells do not change much with temperature"

Most of us have learned to ignore or tolerate you Kimmsr but I can't let it slide when life and limb may be at risk. LP gas pressure increases sharply with rise in tempature. Assuming that there is a leak between storage tank and building plus the pressure regulator is located at gas enterance into building , both of which are common,the leak becomes worse as tempature increases. That is based on principles of science , not on my opinion. "If" you are a firefighter,you should know better than attempting to deminish caution involving matters you know little about. In the words of a once famous man "better to say nothing and let people think you a fool than speak out and remove all doubt."
I know as well as anyone the op's house might sit on the former site of the village outhouse but no back hoes or other source of ignition should be used before checking this out.

Definitely call the local utility companies ...

That "rotting animal" smell may be the mercaptoethanol the gas company uses as a warning system.

I called the local utility company and they have officially ruled out a gas leak. I had no exterior ng lines on the back side of the house but, took the advice of some, here, and eliminated any possibility of a NG leak.

Once again, is there an enzyme solution with which I could drench the soil in this area in an effort to rid the area of a smell without endangering mature plantings?

What kind of mature plantings do you have in the area now? You said the area only gets about two hours of sunshine in the afternoon, so they are shade tolerant.

Is the soil mulched? If so, with what?

Is the soil often wet or boggy?

It's hard to make a suggestion that won't endanger mature plantings if we don't know what those plantings are.

Claire

The area in question is not mulched and, unless I water it, it stays relatively dry.
Plantings include hydrangeas, dead nettle, sedum, and hastas. It is mostly shady and is on the east side of the house so it only gets large amounts of rain when it ISN'T driven by winds out of the NW.

I don't know of any such magic spray for soil. Unfortunately the purveyors of a plethora of indoor cleaning and deodorizing and sanitizing products have given consumers the impression that any problem can be solved with a spray can or a Glade Plug-In. No offense, just making an observation.

Mulch could help but on the other hand if the soil is just soggy and boggy and therefore anaerobic and smelly, mulch will hold in the moisture and will not solve the problem, and more organic matter may just add to it.

Have you ruled out a sewer leak? Where does your sewer line exit the house, and do you have a septic tank or public sewer system hookup?

How is the drainage in this area? Is the soil very wet all the time? Has it always been that way or is it more wet the last couple of years when this odor developed?

There are no sewer lines in the back of the house. I've lived here since 2004. The home was built in '94 and this smell started two summers ago, suddenly. It did not come on, slowly and intensify. It is not noticeable in the cooler months. This area is immediately next to the back side of the house where I have a 16'x16' deck. I've been under the deck, sniffing and looking for anything dead so no avail. I've been on hands and knees in the garden area where the smell originates to the one side of the deck, again, with no luck of isolating the smell.

It is less intense than last year but the weather hasn't really been that warm for any extended period of time, yet, so I don't know how much worse it will be this year.

I am contemplating removing all plants, turning over every inch of the soil to shovel depth and then splitting and re-planting everything from the side of the deck out to the far side of the house in this area (15' x 7').

The soil is on a side of the house that gets sun until 2:00 pm in the summer; however, the neighbors 40 blue spruce, my own 100 year old apple tree (30'x30') and a relatively new-comer to this area, a twelve foot red maple, and another very old pear tree, and a 12' high, thin (reaching for the light) lilac all block the majority of direct sunlight at the ground level until the sun is high in the sky (1-2PM). During that period of time as the bare ground between the plantings is heated up, the smell gets stronger.

The ground there is never saturated but, as is the case in mostly shady areas with plantings, it's damp, two inches deep and deeper.

I have procrastinated but, tilling all of the soil appears to be my only solution.

Thanks to all for their input.

"I have procrastinated but, tilling all of the soil appears to be my only solution. Thanks to all for their input. "

Does that mean you know tilling will cure it but have been looking for an easier solution before going to the trouble?
I was about to suggest/ask you (A) run it by the folks at some of the plant forums to see if one of your plants could cause the odor.(B) consider the possibility somthing was buried on the site in years past ( not to beat on this but if the lot was built on previously,there could be somthing buried including a chemical/fuel tank that has rusted through). (C) do flies congergate around that area (D) if digging random holes intensifys odor (E) if the home has a basement (F) if the gutters dump on or near the area .
Sorry we didn't have an answer but will you please report back after you till the area? Knowledge is gained through experience,be it yours or ours.

You said: "The ground there is never saturated but, as is the case in mostly shady areas with plantings, it's damp, two inches deep and deeper. "

That sounds to me as if you have some sort of drainage issue. In my yard, I have many "mostly shady areas with plantings", but they are almost uniformly dry. My soil is sandy loam and drains extremely well.

Is this area a low point in your yard? If so, tilling the soil may not be a solution, but adding soil to raise the grade might be.

Claire

Based on the info you've provided, I do not have an explanation, nor do I have any reason to think tilling will fix this problem.

If you have some kind of bad smelling bacteria or fungus (or combination of them in the soil) that has decided it likes that spot, tilling will just mix it around. The sunlight, drainage and moisture conditions will not change.

I think you would know if a pack of wolves buried a dead gazelle in there (or equivalent), but if there is 'something' decomposing below the surface you may find it by tilling things up.

As an environmental specialist working on contaminated sites, I'm not terribly worried about old tanks and chemicals, mainly because the smell is clearly "something dead" and not weird chemical smells. Not that it doesn't happen, but leaky sewers and poor drainage are far more common.

Thanks, toxcrusadr, for the input. Since you feel that tilling may even make it worse (and I understand why if it is something dead finally smelling at ground surface level), do you think that an additional two or three inches of topsoil will make any difference?

Where do you have your propane barbecue?
I kept smelling "something dead", too. It was the propane from my barbecue leaking out. The weather got warmer and it started.
Please double check.

Haven't you heard ernie, experts who have worked with propane say it isn't supposed to smell like somthing dead. Propane smells like,,,,,,,well propane,a chemical like odor. Appearanyly you and I keep propane past the expiration date and it rots right there in the bottle. And to think we cook food over that disgusting stuff. Movers and shakers throw propane out with outdated milk and buy fresh. Mine smells somewhere between an overripe dead snake and 5 day old roadkilled armadillo in July. Flies can't tell the difference either because they will swarm a leak. So who are folks to believe when it comes to dead animial odors,self professed experts or a bunch of flies? Any way the op is being coy about revealing information so their mystery will likly go unsolved unless someone volunteers to go out look around in person.

Slips don't count.

This post was edited by klem1 on Wed, Jun 11, 14 at 5:56

Coy? Someone needs to get a life and it isn't me. BTW, I'm 66 yo and not a dumb 66, I may add.

The grill is on the other side of the deck where it doesn't smell. I know how to protect against a gas leak and know the difference between the smell of gas and this "dead animal-like" smell.

This smells like a dead animal and is isolated to a relatively small area ( 15 x 15'). I live on a property that was subdivided in 1993 and my house and the neighbor on the north side of me had our houses built in 1993-94. The small bungalow on the south side was probably built in the '40's.

This smell in on the east side of my house and the south side of the deck. Again the grill is on the east side of the house but, the north side of the deck and is ruled out of my soil issue.

Thanks for the replies. I'll continue to be in a quandary regarding the smell and a solution.

If someone has something constructive to offer, please post. Might I suggest that, before posting, one may want to read all of the posts on this topic before offering their opinion.

Well, if you have ruled out sewer pipes and gas leaks ...

Where do you live? City, state and general area in that city so we can look up plant possibilities

1 - some soil fungus with the "dead animal smell" that releases the smell only at certain times of the year. Stinkhorns are the notorious ones,and they LOVE damp soil with lots of organic matter.

2 - some plant that has seeds or flowers with that smell
(one of the SW acacias has seed pods that smell just like a gas leak!)
Skunk cabbage
Ailanthus (to me it smellslike peanut butter, others say it's offensively rotten)
Other plants have stinky foliage if the foliage iscrushed (Stinking Hellebore, for example)

3 - Maybe the source is nearby and the shape of the ground makes the stench collect in that spot. If a local carnivore leaves bits and body parts nearby, that could account for it.

4 - In some areas, "swamp gases" may infiltrate the water table and emerge anywhere along a soil layer.

=============

The location (city, state, etc.) would certainly be helpful. Zone 7 covers a lot of territory with vastly different microclimates.

A photo of the area would also give us useful information.

Is the property sloped or flat? In particular, is it sloped up or down on the south side of your deck where the smell is apparent?

Are the prevailing winds usually from the NW? (You said "It is mostly shady and is on the east side of the house so it only gets large amounts of rain when it ISN'T driven by winds out of the NW."

I'm still puzzled about the soil between your plantings. You say it's not mulched - is the soil bare, or covered with groundcover? If groundcover, what type? If bare, do you have problems with weeds? What weeds grow in that suspect soil?

Claire

I was thinking about those same questions - what's the soil covered with, and can we see some pics.

klem, I don't want to go off on a tangent but I interpreted kimmsr's original comment that 'gas smell doesn't really change with temperature' as 'it smells the same cold or hot' rather than that the quantity changes. Also, there was no suggestion anywhere that the OP was even using propane. More likely in a neighborhood (he said there are other houses) they are on natural gas so the whole argument about propane tanks heating up in warm weather was a bit premature. There is not that much here IMHO. Now back to our regularly scheduled programming.

You might use the web to research how to get rid of a dead animal smell - all kinds of solutions - not that its a dead animal, but just how to deal with lingering nasty smells.

Did this patch of soil ever get used as a latrine by dogs, feral cats, or raccoons? I have an area on the far side of my pond that gets used by raccoons and when it gets wet and the sun hits it, Puhuuuuuuueeeee.

And another thought ... what was there before the land was developed?

We had a problem something like this...we had a dead skunk trapped under our landing.it was terrible.once we removed it ,the smell did go after sometime. Sorry for your troubles.

Ginko tree? Stinkhorn fungus? Neighbors rendering meat? (Don't laugh -- I lived with this. Ugh)

Scent spreads more in warm weather, so you just may not be noticing it in the cold.

Is any wood (deck, retaining walls, railroad ties) treated with creosote? Smelly black tar like substance.

Is it any wonder op can't deal with the smell when someone comes along grave digging threads every 12 months?

I see what you did there. :-P

Sure would like to know how this turned out.

I have this problem too and would love to hear what solution you found. The corner of our yard, mid-point of our sloped parcel has a foul dead animal smell only when the weather warms up. It can't be smelled during the cool mornings, just in the afternoon/evenings. There is not much direct sunlight, the soil is moist but not boggy, it does dry out. We have eliminated the possibility of dead animals and gas leaks, this is now the second spring it has emerged. No plants appear to be growing that could cause the smell, it is mostly bare soil.

If you want to resurrect a 6 year old thread from the grave,the least you should do is read the thread from start to finish and furnish information and pictures as requested from op,,,,,,,,which he also ignored.