Keeping Potting Media Airy

[MCD]

Thanks for checking; figured it would be small but not 0.

Personally I like to put a (thin) layer of something inorganic like leca at the bottom of the pots, under a bark mix, but not for aeration. I find that depending on the pot shape and drainage hole locations, water can pool at the bottom a little bit, and bark sitting there can start to degrade earlier than the rest.

[tmoney]

oh man, a science discussion! i so want to chime in,,,

so, ray, i think this is of course an interesting topic. however, i have to take issue with a couple things in your report. namely, you used inches in your intro but reported your data in metrics!!! dude, you can't be doin that!

but also i think it would be worth it to design a test for individual particles of each media type. perhaps i will take on such an experiment in the fall (in my copious amounts of spare time)...

also, i would criticise my students for not thoroughly acknowloging the multitude of other variables that could be influencing your final conclusion. not sure you have addressed these fully to draw the conclusion you have. perhaps. i have no skin in this game (and don't know the history you are referring to) but i am not sure i could jump to the same conclusion based on the evidence....

mind you, i don't care either way since we don't grow in foam or grodan, i'm only speaking from a science perspective! so....carry on gentlemen!

[Ray]

Originally Posted by tmoney

but also i think it would be worth it to design a test for individual particles of each media type. perhaps i will take on such an experiment in the fall (in my copious amounts of spare time)...

I don’t have the materials to do the same evaluation for everything…

also, i would criticise my students for not thoroughly acknowloging the multitude of other variables that could be influencing your final conclusion. not sure you have addressed these fully to draw the conclusion you have,

What other variables?

Interestingly, the materials of the container (a plastic document storage tube with cap) do not allow it to get wet and collect droplets. The cubes did hold water between the sidewall and themselves, but as that would be common to both samples, I figured that would be part of the result and present in a real-life situation, either way.

I was concerned about packing density, which is why I weighed the cubes, measured the cylinder, then compacted the cubes to fill the volume.

A “compaction gradient” was possible as a compressed the cubes in the volumes, but tried to minimize that by using a standard weight every inch to compress it. Besides, it seems that the average packing density would be a constant, whether I had done that or not, so the bridging water retention would have averaged out, as well.

Honestly, if you see other potential variables I haven’t, please let me know. At the very least, it gives me a reason to rationalize!

Oh - the change in units came about because the container was a free sample, with inches dimensions, but metric calculations are so much clearer…

[tmoney]

nah, half of that was just to give you a hard time, ray. i don't think enough people on ob do that!!

but the main variable i was considering which i was hoping you would address was shape of the media particles. also, there are different types of packing peanuts, and while we have common access to some, i think others may not. ok, grodan is probly pretty consistent from place to place. but certainly particle shape and size will affect water retention. which is why i suggested an individual particle trial. also, the compaction which you mentioned, as well as i was thinking in your description you had a basically flat layer of foam at the bottom which seemd to me would certainly cause more water to build up due to slower drainage.

the angle of which you drain water from the container was brought up in this thread by somebody else, and that is something which would need to be controlled at the least. it stood out to me because i have always done that with all of my houseplants (and now do with orchids), and it always amazes me how much extra water comes out just by tipping the pot slightly.

plus, i have spent the past two weeks scrutinizing student independent investigation reports for flaws in the scientific method, so i was still in work mode when i read your post. aaaannnd, i really really really hate tv science for presenting limited evidence but stating a matter of fact conclusion as if the matter is closed.
it never is in science...amiright?? anyways, just throwing stuff out there that i was thinking of when reading your results report.

[Dimples]

Originally Posted by MCD

I find that depending on the pot shape and drainage hole locations, water can pool at the bottom a little bit, and bark sitting there can start to degrade earlier than the rest.

I combat the pooling by placing the pots on an absorbent towel after watering. The towel wicks out the water pooling at the bottom of the pot and it also removes some of the water held in void spaces higher in the pot due to the cohesive properties of water. It's not a method suitable for very large collections but it works very well.