Fake plants behind speakers a good idea?

I have 2.5 feet from the back of my floorstanders to the wall, and 3.5 to the side, I have seen some people placing silk plants behind their speaker, good idea or not
would the silk plant cause diffraction or absortion
Silk plants aren't big enough to do any effectively absorb or diffract sound waves.
I dont think it will harm the sound but I dont know how large and dense the "plant" will be, my wife is thinking of doing the same thing, but I am not too sure about it.
Try some real plants.The dirt acts as a bass traps.
Dont ever water as it muddies the bass.

More than one respected speaker designer has told me that large plants carefully positoned can help a rooms sound.
I don't know what type of speakers that you have, but many maggie users, utilize silk ficus trees behind their speakers for diffraction. Contrary to what beavis says, the do apparently work.
Silk works real works better, Infact plants in the room really help also.
If your system is really, really good (excellent), then use fake plants and you will be pleased with how the good sound actually makes them grow!
I have a 5' tall fake tree/plant in a back corner of my setup. I measured the room response with and without it. I found no difference in SPL's at any frequency. Also, it does't seem to effect imaging positively or negatively.
Live plants enjoy music; to set plastic ones behind the speakers is to waste the "psychic energy" which real plants could enjoy. However, it was found that in basement home theaters plants were not influenced positively by the music, and they died. This is why you never see plants in commercial theaters.
I have used the silk ficus trees back from the days of Martin Logan's - placed behind the speaker and it did help with diffraction and imaging. I have em, so they usually stay in the rear front corners behind the speakers. I have also seen this setup in many showrooms...

Have I A/B'ed with and without em ? nope.
Kirk, perhaps no one informed you that you only get definitive results with Radiohead's "Fake Plastic Trees". Try it again. You'll see. It's all about synergy.
To start, I have a pair of FocusAudio fs 788, I bought a pair of 5' silk plants. My room is approx. 14, 17 they seem to have more of an absorbing effect, lost a touch of low and mid band which in turn made the high end more prominant, but of course thinner sounding....anyone want to buy a couple silk plants?
Funny that this thread topic just came up.

A week ago I bought a pair of speakers and set them in the same place as the old pair of speakers that they replaced. Sure, I adjusted them a few inches. A little toe-in here, an inch or two forward there, etc. They sounded fantastic.

We are going to be painting the room this weekend so I started moving furniture and plants out of the room first (the system was the last thing to go). Sure enough after moving a 4 foot tall potted plant from the right rear corner (about 2 1/2 feet to the right and 2 feet back from the right speaker), the bass got really boomy.

Now you tell me, does a 4 foot potted plant with a ceramic pot equate to a bass trap? I dont think so.

But damned if it did not have a major effect on the sound.
I kid you not, I believe the a Japanese man/company has discovered how to make living plants play music! That would be way cool. I remember seeing it on the web...
That would make for surreal surrounds.
I once had real plants around my left speaker. A friend brought a Crown RTA over. When I looked at the output, all I saw was a comb filter effect. I said what is this? He said let us remove the plants. Afterwards, there were still problems, but the comb filter was gone.

I should say these were big leaved plants. Maybe a Boston fern would not do this. I have no plants in the room where I have my system.
the best plants to have around your speakers are ones you can smoke! ha ha! at any rate...happy listening!
I once had some fake plants that played music. They sounded better when I put some speakers beind them.
It does a bit of both, alot depending on the density of the tree. Still however, it does improve in situations where either aborption or diffusion is needed. Plants help with slap echo as well. Still it depends.
For instance I find dipoles and planar types don't do as well with plants behind them, nor any sound treatment, save some diffusion. Yet it's most often the opposit with dirrect radiating traditional speaker designs.
It seems my experience with plants has also been that they work at least better sometimes in smaller rooms, where absorption only would be too much, and diffusion better. Here plants often work cheeply if need be.
Like anything, you need to experiment to find out in your room.