I would say that's perhaps an oversimplification? Adding a wick helps to reduce perched water, but does not address mix overall water retention or gas exchange. Other important factors to consider also include (but are not limited to) soil CEC, longevity, and compaction.

The amount of wicking determines the drainage rate, limited by the intrinsic drainage rate of the soil. Consider a plastic pot with an open bottom. There is total contact with the ground. There will be NO perched water. Any degree of reasonable wicking guarantees NO perched water. There is no need for fancy soil mix with respect to drainage concerns.

Yes, this is the pot in pot or pot on ground technique. =)

The next level beyond that is the plant-in-ground technique.

So no need to spend money & time on preparing special soil mix or replacing the potting soil due to breakdown. Just use the same kind of soil for the container that would work if the plant is planted in the ground & make sure there is adequate contact with the ground or other drainage sink.

The ideal with regards to the scenario you are describing is a raised bed with an open bottom. For this you would use the same soil as the site so that you have a continuous soil column, Then people put plants in containers and used field soil and it was problematic, so they buried them thus making mini raised beds. But having to bury the pot in soil is a big problem because well if you had access to the ground you don't really need a container. So that's where coarser media come into play. They allow you to get away from the effectively infinite soil column and have a plant in your house or on your concrete patio without it being a total PITA.

Also, the bottom of the pot will act like hardpan and create a PWT.

Now that is just the PWT which isn't the biggest problem imo. The biggest problem in containers is flooding. when you have an opening for water (top of the pot) that is the same as the exit then no flooding can occur. But as soon as you reduce that exit aperture, it can be overwhelmed. This means that when it rains, the pot can flood. When the pot floods, the medium saturates depending on how long the medium was flooded and how moisture retentive it is. Saturated field soil is a problem for farmers with infinite soil columns. It's also a problem for container gardeners. So if you have a container that floods, you need a medium that can flood, saturate, and not become an anoxic mess.

I would also add that many ppl grow plants in containers that do not sit on ground - they are on furniture (indoors or out), shelving (solid or open, wire type), on decks, on windowsills...so there comes a saucer of some kind and no 'contact with ground'...

I concur with Nil13. You'd have to contact with most of the bottom area, not just a 1/2 inch drainage hole, ergo you would not be planting in a a pot but a tube?.

I'd just plant them in the ground, call it a 'bed' and be done with it.

My containers are on the 2nd floor deck railing, so I can sit on my deck and watch the hummingbirds. Contact with the ground is completely off the table, so it's 5-1-1 for me.

You don't need contact with the ground. You need contact with a drainage sink. If the plastic pot is 10 ft in the air, some small towels or similar dangling out of the drainage holes allow the air to evaporate the water in the towels & thus create the moisture differential that create the capillary force. A dime size hole for a 5 gal pot is not enough. The drainage holes have to be large enough to sustain the desired drainage rate. There is NO hardpan. Unglazed ceramic pot evaporate out the sides so the bottom holes are not the only way out for water.

In a tray, place the pot on top of a bed of sand. the water goes into the sand, evaporation occurs, capillary action draws more water out. No need for ground contact. As long as there is a adequate path to get rid of the water, drainage is not a problem.

Your sand hypothesis is flawed. Any difference in texture with the container medium will cause the medium to saturate before releasing to the second texture profile.

wicks can definitely draw water out, but they also plug the drainage holes and facilitate flooding of the container which is a major problem.

Then there is always the problem of the aluminum in field soil binding with P and making it unavailable thus necessitating heavy P applications.

Here's a link that illustrates the work done on water and soil texture differences

http://gardenprofessors.com/container-planting-intuition-vs-reality/

Good Video on understanding the true nature of water movement in soils. Water Movement in Soils.

The opening statement in the video states Capillary forces are the predominate forces governing the movement of water in dry soils, with gravity playing a minor role. Gravity is not the principle force moving water in unsaturated conditions. This is main principle to remember. Gravitation forces have more effect in very coarse mediums only( Low Capilllary Forces). Also note the curve formed, during the capillary rise demo between glass plates. This traces out the Mathematical Capillary Rise Function, The same as the PWT height versus particle size function.

above Perched Water Table Height in centimeters versus Medium Particle Size in millimeters.

geo przm- you have a good understanding of the principles, and the reasoning/correlation of possible solutions. But still maintaining a minimum particle size > 0.5mm is still a good idea for small containers. Growers are using capillary sinks all the time, from a folded paper towel under a pot to Capillary mats with a 2 to 4 inch growbench overhang.

Capillary Irrigation Systems work well, because of the constant supply of water without saturation. Ideal air/water ratios in the medium.

The Statement that a medium becomes saturated first, before flowing out the bottom of a container. This happens with whatever medium you use. This happens because at the medium/air interface, capillarity drops to zero at the interface. The water will start to build a positive pressure column PWT, until strong enough to cause drainage from the bottom of the container. Water is normally under negative pressure or Tension in Unsaturated Conditions. Water is moving as a film, rather than filled pores of water. A Saturated Condition is when the entire pore space is water filled, with no air present.

Addition: The good thing about Water/Medium parameters they can be actually be measured , and tested by the individual grower. This eliminates the dependence on Speculations,Gardening Articles, and Opinions. Physics is basically simple, and the application of Superposition simplifies more complex systems. Capillary Forces are in every possible direction at once, were Gravitational Force is modeled only toward the Earth's Center of mass only. I noticed that growers tend to think, that Gravity alone is responsible for downward water movement. Gravitational Water is the excess between Saturation and Field Capacity, and moves from mostly Gravitational Forces ( Forming Aquaifers etc.). The Study of Watersheds is a great topic also. Basically growing in coarse or gravelly mixes is just Hydroponics, with a little extra WHC added to the mix. Nothing Special or Superior about it, just a different approach to plant culture

The video clearly shows the clay layer under the silt layer immediately pulling water down as soon as the water reaches the clay layer. The video & photos simply show the capillary force as function of the particle size. Fine particles have greater capillary force than coarse capillary force. The use of different particle size in horizontal or vertical layers allow some interesting possibilities in controlling water movement. One part of the video shows this with a slanted coarse vertical layer in contact with the free water.

So using a layer of coarser material under the container with finer material insure the container is fully saturated ( all roots are fed water ) before pulling water out.

A layer of the SAME soil under the pot means NO discontinuity and the water will be pulled out as soon as the water reach bottom. The container is NOT guaranteed to be saturated.

An unglazed clay pot will have effectively finer particle size than any likely container soil and thus pull water out immediately upon contact, before all of the container soil is necessarily wet ( this will be affected by the evaporation rate ).

If it is indoors or under cover, trays are ok. If outdoors and if it rains while at work the tray fills up they sit in water all day. Then I have to take the pots out of the trays, dump the water and replace any of the media that fell out.

I still pass.

I have PWT in my containers sitting on the ground. Based on my experiences with several sizes/shapes, I respectfully disagree with you.

I am not sure what the overall results, you are designing for. As far as water levels in any sinking reservoirs. There are always overflow holes in the sides of the reservoirs at maximum water table height or aquifer desired. Capillary Sand Beds have been used for decades at Professional Propagation Nurseries. A couple examples of Capillary Mat systems using Polyester Felt Fabrics.

Actually you are trying to avoid Saturation, which is the point when there is no air in the growing medium. Most growers aim for a 50/50 air/water content in the pore spaces.

Sidenote: Floodplains are stratified in a similar fashion, with coarser materials overlayed with a silt loam, due to soil settling from suspension. Fine to coarse interface, movement checked by capillary differences, Coarse over fine texture interface slowed due to slow transmission of moisture thru the fine layer,

Pamela, who/what do you disagree with?

Not to say I don't have PWTs. It depends on the plant. I have Cardinal Lobelia in bag potting mix (Gardeners Gold) sitting in a 2 1/2 inch deep saucers I purposely keep full of water. They DEFINATELY have PWTs! I can't get them to flower otherwise. My others would be dead in 3 days if I gave them the same.