I did an interesting experiment today and took some photos for others to see the results. I created containers with different sizes of grit as follows:

- 3/16 inch crushed and washed rock, which was sourced as Cherrystone #2 poultry grit
- 1/8 inch crushed and washed rock, which was sourced as Pumice #8
- 1/12 inch crushed and washed sand, which was filtered from Olympia #2 sand
- 1/20 inch crushed and washed sand, which was filtered from Olympia #2 sand
- Extremely small particles, which were from Olympia #2 sand

I dyed the water with green food color so that the perched water table would be easier to see on the sides of plastic container cups. I marked the level of the perched water table with a green line in the first photo.

The results of the test:

1: Tapla was right that the two particles that are larger than 1/10 of an inch did not have any perched water. These are the 3/16-inch and 1/8-inch samples.

2: The 1/12 inch rock had only one inch of perched water, and honestly, if this were part of a gritty mix with turface, I think such a small reservoir of water at the bottom would be a good thing, as the turface would quickly soak it up over the first day or two. At a minimum, such a small level of perched water seems inconsequential. I would be interested to hear what Tapla thinks about that.

3: The 1/20 inch rock had two inches of perched water, and that looks like too much for a container "purist" who wants to use larger particle sizes to keep perched water low.

4: The container with small particles was totally out of control, with perched water going all the way to the top of the soil level. I am sure it would have gone higher if I had added more soil.

Way to go! Strong work.

When you consider how potentially damaging or dangerous a perched water table is root function/health, it's essential to consider the length of time it's going to be a factor. A 1" PWT that hangs around at the bottom of a plastic pot for several days can limit root function of roots within the max ht of the PWT, and has the potential to set the stage for root rot. The same 1" PWT in a clay pot would have less potential for harm, all else equal, because the gas permeable walls of the pot could ensure greater water loss via evaporation, and would probably be considered a blessing to the grower if it means the difference between watering once or twice per day, or every other day as opposed to every day.

The plant would prefer that the medium holds no perched water and the grower waters as often as necessary for the plant to be properly hydrated, but the plant doesn't get a say. Growing is very often about compromises. How many of us make our own media, even though they can be much easier to grow in than >95% of commercially prepared media?

My view with regard to the gritty mix is, why make it if you're going to undo what I consider its most valuable property? It doesn't hold more than a tiny amount of perched water which can easily be removed in pots easy to handle. If one is after a highly aerated medium and doesn't care if it holds some perched water, the 5:1:1 is easier to source and make, and less expensive as well.

I'm not making any judgements about what anyone decides to do, just trying to provide reliable information/commentary that can be used to make decisions that affect our growing experience.

@pone31 I particularly enjoy exchanges with growers interested in getting more for their growing efforts and who exhibit as much enthusiasm as you.
Al

Always good to have some photographic evidence of a common physical/horticultural phenomenon. Great job.

tapla said: Way to go! Strong work.
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My view with regard to the gritty mix is, why make it if you're going to undo what I consider its most valuable property? It doesn't hold more than a tiny amount of perched water which can easily be removed in pots easy to handle. If one is after a highly aerated medium and doesn't care if it holds some perched water, the 5:1:1 is easier to source and make, and less expensive as well.
...
@pone31 I particularly enjoy exchanges with growers interested in getting more for their growing efforts and who exhibit as much enthusiasm as you.
Al

Thank you for your positive feedback Al. It can be very difficult in these groups with each person giving completely different advice, and so often people have no interest in applying science to answer a question.

To answer your question on why make the gritty mix with a *tiny* amount of perched water: the answer would be to increase the moisture retention in the upper layers of the soil. That might give you a few more days without a need to water, and for some plants like succulents and cactus will result in more water storage in their leaf system.