Hi guys,

Today, I was pondering about something that happened with a plant 3 years ago. I would like someone to try and help me solve this mystery.

Here's some backstory.

When I lived in Post Falls, Idaho, we had a Peace Lily. It was a good plant, but it always seemed to struggle. We do not know why.

Then, we moved to Nampa, Idaho in 2017. The plant was still struggling, even though it got adequate light and adequate water.

Then, We were moving again in 2019. We could not bring the plant with us. It was struggling anyway, so we decided to discard it.

This is where the mystery comes in. When we were discarding it, we took the plant out of the pot, and found that deep down inside this very large pot, the soil was VERY hot. Hotter than it was in the house. If I had to guess, it was maybe 100°F. Maybe more.

Here's my question. What caused the soil to get so hot? This has been baffling me and stumping me for years.

My best guess so far is that somehow the dead roots were getting composted on their own, without me knowing about it.

Can someone at least try to help me solve this mystery?

Jared

I agree with you. You were unwittingly composting the Peace Lily.

Thank you. You just help me solve a mystery that's been in my head for three years. One thing still confuses me, how did the composting process start? I have no idea how it started. There was no organic matter in the potting soil. Makes me wonder how the heck this process of composting started?

This may sound crazy, but maybe the plant discarded some of its roots to actually make a compost for nutrients for itself.

Like I said, that's a crazy idea.

Something was creating heat. If you got the right bacteria going in an anaerobic situation (created by densely packed overwatered or breaking down soil), that would create heat. Did it smell slightly of sulfur? Or rotting vegetables?

DaisyI said:Something was creating heat. If you got the right bacteria going in an anaerobic situation (created by densely packed overwatered or breaking down soil), that would create heat. Did it smell slightly of sulfur? Or rotting vegetables?

I actually don't remember if there was a smell. However, I do remember that the soil was densely packed. So was the root system.

Soilless soil is usually heavy on peat. With a little more effort, you could have had a peat fire.

I don't think that's a big enough "pile" to generate heat, and a lot more air would be needed for heat to occur.

purpleinopp said:I don't think that's a big enough "pile" to generate heat, and a lot more air would be needed for heat to occur.

Regardless, heat did occur. I do not know why. This is truly a mystery.

It is, I couldn't think of an alternate theory, just that I doubt it was from decomposition on such a small scale and with so little air. It's not the kind of thing that can be decisively solved at this point, but interesting.
Where was the pot at the time? Any chance that the location was the source of heat, like if it was where the sun could shine on it, or on top of a fat old (got hot on the top) TV? Maybe the pot was bigger than my first reaction, and there was more air. If a foul odor wasn't noticed, anaerobic decomposition wasn't occurring but if it did happen to be hot composting, there shouldn't be any foul odors.

I've repotted hundreds of plants and never found any hot roots like you describe.

purpleinopp said:It is, I couldn't think of an alternate theory, just that I doubt it was from decomposition on such a small scale and with so little air. It's not the kind of thing that can be decisively solved at this point, but interesting.
Where was the pot at the time? Any chance that the location was the source of heat, like if it was where the sun could shine on it, or on top of a fat old (got hot on the top) TV? Maybe the pot was bigger than my first reaction, and there was more air. If a foul odor wasn't noticed, anaerobic decomposition wasn't occurring but if it did happen to be hot composting, there shouldn't be any foul odors.

I've repotted hundreds of plants and never found any hot roots like you describe.

The pot was by the south facing window. However, the heat in the pot was hotter than the heat in the house. MUCH hotter.

And yes, this was a BIG Peace Lily. Big pot.

And for the record, it was not the roots that were hot, it was the soil.

South facing windows can get pretty toasty. Just wondering, what color was the pot and what was it made of? And how close to the window was the pot?

woofie said:South facing windows can get pretty toasty. Just wondering, what color was the pot and what was it made of? And how close to the window was the pot?

Pot was gray color, made of plastic. I'd say it was about 1.5 feet from the window.

I still think, under the right conditions, a pot of soil could generate its own heat.

Oh, and you didn't mention what time of year this was. I have south-facing, double pane French doors here and I use the heat from them to warm my hands. (It's currently 35 deg. outside) I stuck a thermometer about 1-1/2 ft away from them. Right now, that thermometer is showing 83 degrees. The room temperature is 71.

jnicholes said:
When we were discarding it, we took the plant out of the pot, and found that deep down inside this very large pot, the soil was VERY hot. Hotter than it was in the house. If I had to guess, it was maybe 100°F. Maybe more.

Not warm all the way through, hot in the middle of a very large pot. If a warm window was the cause, the soil would be cooler in the center, not warmer.

DaisyI said:

Not warm all the way through, hot in the middle of a very large pot. If a warm window was the cause, the soil would be cooler in the center, not warmer.

Very true. However, if the pot had been moved from that warm (hot?) window area for some time before emptying the pot, the outer soil would have had a chance to cool faster than the inner area. Not trying to be argumentative, just trying to think of scenarios that would account for that hot inner soil.

purpleinopp said:I don't think that's a big enough "pile" to generate heat, and a lot more air would be needed for heat to occur.

The heat starts with lack of air. The kaboom would be the introduction of air.

That's not what I've read, or what I've experienced. Air is required to generate heat. Anaerobic composting is often referred to as and used interchangeably as terms with "cold composting".

I note that no one here has said aerobic composting does not produce heat, but you seem to imply anaerobic activity is hotter, Daisy. I've never heard this before, either. What can you tell us that breaks the status quo?

Leftwood said:I note that no one here has said aerobic composting does not produce heat, but you seem to imply anaerobic activity is hotter, Daisy. I've never heard this before, either. What can you tell us that breaks the status quo?

Nope, didn't say that. I don't know what you read to give you that idea.

I did say anaerobic decomposition will produce heat. I did not say it would produce more heat than aerobic decomposition. I did ask if Jared smelled anything as that would be part of purtrification. He couldn't remember. I did joke if he exposed his peat based, too wet, solidly packed potting soil to air, it could explode. That was a joke. I'm from farm country and exploding hay bales were not unheard of. Also exploding cow carcasses.

We don't really know why Jared's potting soil was too warm in the center but, given that the soil was old, soiless, packed and wet, anaerobic decomposition was my first thought. It produces a small amount of heat but nothing like aerobic decomposition. But also produces a smell because the decomposition is prodcing methane.