Riddle me this:
  There have been many great (ongoing) threads on the forum regarding Sub Irrigated Planters or Self Watering Containers of various sorts.  Here are just a few relatively recent ones (there have surely been others in the past)
The 2 minute $2 SIP(SWC) - Pictorial Tutorial
Convert any small container into a SIP...Sub-Irrigated Planter for Growing Cuttings

  Many different overall designs were discussed over the course of these and other threads, but what I'm wondering about specifically is the wick.

• Some designs use a soil wick, typically a soil-filled container that drops into the water reservoir -- the water-saturated soil wicks water up into the drier soil above the reservoir.

• Other designs use a fabric wick, typically some absorbent fabric that has one end hanging down into the water reservoir and the other end up into the soil area above the reservoir.  The fabric wicks the water up into the drier soil above the reservoir.

Jim,
A fabric wick will work with a wider range of potting mix ingredient and recipes. Fabric wicked SIPs are not as reliant on the potting mix porosity as a "soil" wicked SIP. The fabric wicks are able to distribute the water into the potting mix.

Soil wicked SIPs rely on a high porosity mix, which actually means that it has smaller particles and smaller air spaces for better capillary water transportation (which actually translates to less aeration). Due to this design feature, the bottom of the container in the area of the soil wick is usually saturated with water.

The wick sizing is one of the most important element of any successful SIP design.
Soil wicks in successful SIPs are usually about 10% of the planters cross sectional area, so the size is easy to calculate.
While fabric wick sizes have to be tested for every material used and in every container and configuration. That's why the Pellon Thermolam Plus TP970 fabric was used and is recommended, as a means of standardizing and reducing those variables.

Although fabric wicked SIPs have their advantages, they use an additional material (fabric) which increases the cost and complexity of the SIP design.

Pete, Doug,
  In the other threads, I think a lot of the debate may have been regarding the use of fabric wicks on small SIPs (e.g. those made from soda bottles or even cups). 
  Maybe I should narrow the scope of my question:  Do you think that a larger SIP, say a 3-gallon bucket size or larger, would be more forgiving?   (I can definitely see where it might be harder to strike a balance with small SIPS for newly rooted cuttings...so let's remove that from the equation.)

  On a larger SIP -- If the fabric wick simply remains on the bottom of the soil (as opposed to being trailed up the sides), don't the soil and fabric wick serve the same purpose -- i.e. to bring water in contact with the very bottom portion of the soil...to then be pulled up into the rest of the soil?

  Pete -- at $3-4 per square yard, the Thermolam seems inexpensive, especially when you factor in how little you need per SIP and that it saves you the cost of wick container and the trouble of cutting a properly sized hole...
Cheers,
Jim

Doug, Are you meaning with soil wick?

Jim,
The 2-liter SIPs work with or without the Fabric wicks due to the bottle's neck which forms an appropriately sized "soil wick". Many of the Mini SIP Cups have been constructed with over sized reservoirs and or over sized wicks, which quickly saturates the mix, but is actually an easy fix as I explained in the SIP topic. Because mini-SIP use in fig culture is still experimental, the proper procedures and instructions are not yet developed. The same way that the procedures and instructions for the accepted and documented rooting and growing methods,Paper towel, Sphagnum Moss, New Baggie, Small and Large Cup, Peat Pot in Cup, etc when followed will almost guarantee an increase in success rates.
Doug has posted on one of the most important aspect of their use in fig cutting culture, it is that the reservoirs should never be filled in the early rooting and growing stage before the cuttings have callused and begun to "grow" and that the water shoud be metered after this period.

Soil saturation is one of the main design features of all successful SIPs. The soil is saturated and capilliary action stops, when the water is used by the plant, capillary action resumes to keep the soil wet. Although saturated, the soil is  still usually well aerated. For fig cutting culture, mix saturation almost always means failure, so the operational procedure (instructions of use) has to be changed for that application only.

Standard Sized SIPs with fabric wicks can use a variety of potting mixes due to the fabric providing  most of the needed capillary action. In your example of a 3 gallon container, a 1/2" to 3/4" hole can be placed at the center for four 1" to 1-1/2" wicks. The wicks should extend down into the reservoir and up into the mix, the wick size and length are completely dependant on the potting mix. For a high porosity mix, the wick should only cover (fan out on) the bottom of the planter. For a lower porosity and more aerated mix (larger particles), the wick needs to extend up into the mix possibly in the perimeter of the pot. The design is standard and basic, but the wick size and length has to be tested with the potting mix that will be used. For standard peat based mixes with 75% or higher Peat content, the wicks across the bottom of the planter will usually be sufficient, but the first construced planter should always be tested over several days and with a full reservoir, and initially with only a half full planter to be able to observe the wicking action and aeration..

Yes, the Pellon fabric is inexpensive, readily available and is durable enoughf for a few seasons of use.

To clarify a point on the amount of water in the reservoir (assuming a large SIP)...
...eventually the amount of "perched water" in the soil will reach some equilibrium (however high that ends up being for the particular soil mix) and the amount of water in the reservoir won't matter, right?  I mean, the reservoir could be completely full or nearly empty, but the wick and soil won't wick up any more water until it is needed (i.e. until the plant roots suck it out.)  That is the point of the SIP/SWC, right?  It is kind of a "set it and forget it" kind of thing....as long as you keep the reservoir from emptying out completely, you're good to go.  And if there's a drain hole, there's no such thing as overfilling it, right?

Pete, in my non SIP pots I've typically used a 5-1-1 mix (pine bark fines - promix HP - perlite).  The Promix HP has a bit of perlite, so it isn't quite 5-1-1.  I've also used a 5-1-1-1 mix where I add an additional one part calcined clay  (NAPA floor dry or some equivalent product), which seems to hold a bit more water.  How do you suppose they would compare?  There's much, much less than 75% peat, but the pine bark fines contain a wide range of particle sizes (larger and smaller). 
I guess the only way to know for sure is to build one and test it out, as you suggest.
Jim

Jim,
Yes to all three questions, in a regular SIP the water sits in the reservoir and is extracted by capillary action when needed automatically. Capillary action is controlled by the saturation of the potting mix, when the soil is saturated, its off when the soil is drier, its on.

I've been using a 5-1-1-1 mix also. My SIP mix will use the same ingredients, but at different ratios, with an increase in Peat and a decrease in Pine Bark Fines, but it still has to be tested. Yes, the SIPs are so simple to build that it would only take  a few minutes to assemble a 3 gallon sip from a nursery pot for test purposes.

Full disclosure... all my existing 5 gallon buckets will be converted to Fabric wicked SIPs, using a single 3/4" hole in the bottom for the Thermolam Fabric wicks.

needaclone, I follow what you are saying and I too have been struggling with this. I don't want to chance my cuttings to experimentation especially since I have no backups yet. Water will seek it's own level so simply plopping a pot in water may or may not promote capillary action. If the water in the reservoir is half way up the pot then the water will be half way up in the pot. I grew african violets when I was young and used a wick with them, this is why I am having trouble grasping the need for the wick to be soil rather than fabric.

Sorry, you're talking about fig trees or about cuttings ?
IMO, the more water in the reservoir, the more water in the potting mix. - The overfill drain helps a lot or you have to be careful when watering or you'll turn the pot into a swamp.
You shouldn't allow water to camp in the reservoir for cuttings - you could let some for trees.
You should allow the reservoir to get dry - be it trees or cuttings - just my advice .

Milehighgirl, Jdsfrance,
A SIP is more than the wick (Soil or Fabric), its an entire design concept with several parts. Reservoir, Planter, Aeration Platform and Wick. They all work together to keep the potting mix aerated and wet without being waterlogged. The properly sized wick (fabric or soil) will move water through capillary action and that capillary action is controlled by the soil's moisture content. The Aeration Platform serves to keep the bottom of the planter out of the reservoir, provides air to the mix and also keeps the mix from getting waterlogged, any excess moisture drains back down to the reservoir.
  

Placing a pot directly in a container of water "half way up" will saturate and quickly water log the "bottom half" of the planter. Water will always be drawn up to the top half through capillary action. For plants that do not like wet feet this could be a problem. In the case of the submerged pot the entire pot has become a "wick".

Fig cuttings grown in the Mini-SIPs are an exception, not because there is a problem with the mini-SIP, but due to the Nature of Ficus Carica. The fig cuttings need minimal moisture to initiate rooting, for callusing and initial growth if the mini-SIP reservoir is initially filled, the cuttings may rot. This condition will not and does not apply to older Fig Plants in Properly designed SIPs, where the reservoirs can remain full at all times.

OK, so I'm trying to read up on SIP/SWC design and I guess I still haven't come across a basic piece of information.    This question is targeted toward SIPs for trees of various sizes, not for newly rooted cuttings.
  My question is, how can you tell when you have a good balanced design of wicking ability vs soil porosity?  How high up the container do you want the water to be wicked?  Would the goal be for just the top few inches to be relatively dry?  And how radically does the balance level change if you have the top of the container sealed with plastic, since you won't lose anything to evaporation out of the soil?
  I remember reading something about perched water levels in various bottom-watered Talpa mixes...but I don't recall if there was a guideline for what level was appropriate.
  Sorry for not doing my homework better before posting...but I don't want to stress my trees out by making their feet either too wet or too dry!
Thanks,
Jim

Jim,
During testing of your SIP design with your mix, you should be able to tell if the bottom of the container is fully saturated or if it is retaining enough aeration by simply dumping the container or digging down into the container. There are also several members that are successfully using SIPs and have posted their mix ingredients.
If you wanted to do a better test, you could place your mix in a tall clear cylinder and measure the actual height of the saturation zone of that particular mix. Keep in mind that the SIP wick is actually acting as the "Saturation Zone" or "Perched Water Level"of the planter by changing the mix ingredients (porosity) and or the height of the planter you can also change the maximum height of the wicked water. I posted the following to another Topic: Easy, Simple and Practical Tricks to Increase Potted Fig Cutting Survival Rates

Quote:

This document provides simple explanations and procedures for increasing success rates. Although the subject of the article are plugs, it is completely applicable to growing out fig cuttings in small containers.
http://ohioline.osu.edu/hyg-fact/1000/1251.html

Quote:

 

The idea still persists that drainage from containers can be improved by adding a layer of coarse material, such as gravel, to the bottom of the container. In reality, this makes matters worse because the saturation layer is simply moved up, reducing the unsaturated portion of the container (Fig. 6).

For my SIPs, I'm putting pure peat moss in the wicking chamber and Pro-Mix BX in the main mix.  It will be interesting to see how well it works.

Bringing this thread back to life in hopes of hearing some outcomes of how well the SWP designs have worked for everyone and possibly what did not work. Any other links to topics with reviews of several years of SWP's use welcome!

This will be my 2nd growing season using swp's, both homemade and store bought. All I can say is that the growth rate is very noticeable when comparing swp's vs standard black nursery pots. 

Most of us are short on space to keep many varieties and  wait years to get great tasting figs meaning if we have to wait 3-4 years for a fig but the tree is kinda skinny I don't believe you're getting it's full potential.
I have a 4 year old in a 15gal standard pot and a small 2 year old in a swp(1year in swp) that has already out produced, fig wise, the 4 year old and are now the same size and the swp tree looks healthier!!!

So if you want to figure whether or not to keep a fig faster, swp's are the way to go...