You may be assigning to perlite that which is probably more rightly attributed to gravity. I'll explain. Even if there was a consistent volume of perlite mixed evenly into the soil from top of pot to bottom, it wouldn't have much impact on either the drainage (flow through) rate, how much air the soil holds, or the height of the perched water table. If you mix perlite into pudding, it doesn't increase aeration, drainage, or the ht of the PWT because the pudding simply surrounds the perlite and by doing so, rods of of any significant value UNTIL the perlite becomes a very significant fraction of the soil. Pudding + 15% perlite yields a medium with virtually all the physical characteristics of pudding, but perlite + 15% pudding is a different story. In your case, when using the heavy medium, the soggy layer at the bottom of the pot would have been there anyway, but that's because gravity dictates that the water moves down in the pot until the capillary attraction of the soil is exactly as strong as the pull of gravity. The perlite, in smaller volumes, can't change that balance, but it does take up some space that would otherwise be occupied by water, so it reduces the o/a water retention of the soil without significantly increasing aeration or the ht of the PWT. When using soils that don't support significant volumes of perched water, you get a much more even colonization of the soil by roots. Since the entire medium is well-aerated, you don't get the roots running round and round the inside pot wall looking for (growing only where there is ample) air, though roots will start circling if the planting is left to go badly root bound. Al

Here is the recipe (excerpt from the thread below): *For long term (especially woody) plantings and houseplants, I use a superb soil that is extremely durable and structurally sound. The basic mix is equal parts of pine bark, Turface, and crushed granite. The gritty mix: 1 part uncomposted screened pine or fir bark (1/8-1/4") 1 part screened Turface 1 part crushed Gran-I-Grit (grower size) or #2 cherrystone 1 Tbsp gypsum per gallon of soil CRF (if desired) Source of micro-nutrients or use a fertilizer that contains all essentials I use 1/8 -1/4 tsp Epsom salts (MgSO4) per gallon of fertilizer solution when I fertilize if the fertilizer does not contain Mg (check your fertilizer - if it is soluble, it is probable it does not contain Ca or Mg. If I am using my currently favored fertilizer (I use it on everything), Dyna-Gro's Foliage-Pro in the 9-3-6 formulation, and I don't use gypsum or Epsom salts in the fertilizer solution.* http://forums2.gardenweb.com/forums/load/contain/msg0214580016564.html

Hi, PB ;o) Well, your mix initially has some volume or loft because the small particulates don't fit well together yet. I don't think it's so much a problem with soil collapse because of decomposing. Rather, I think that watering, over time, continually rearranges the particles so they mesh together & this eliminates the loft or decreases aeration and causes what you observe to be shrinkage. Increasing particle size, more uniform particle size (not always practical to try to achieve for the average grower) and using a bark-based soil can help to greatly reduce shrinkage and insure aeration. You'll need to address the possibility of not enough water retention in whatever mix you come up with, but I'm thinking that if it becomes an issue for you with a more aerated mix than you're using, the water retaining polymer crystals might be a solution. I am finding it difficult to get affordable perlite. A 2-3 cup bag is around $3.50. Keep looking. I promise it's available where you are in 3-4 cu ft bags (huge) and they'll be less than $20, probably around $15. Ask at nurseries or greenhouses, they'll have a source if they don't have it. What is your opinion on using rabbit manure as the 'manure' part of your mix? The original thread you read is very old. I first posted it in spring of '03. It hung around quite awhile & then I posted it again in Spring of '05 and then JD reposted it this year. Since I wrote it, I've stopped using any manures. Too many weeds in some & it breaks down too quickly to please me. The rabbit manure would fall into this category & is probably best saved for the garden. There are lots of micro-nutrient additives out there, but I'm pretty confident you'll not find household ingredients to supply them. I can help if you write off forum, or you can search out fertilizers that contain them and use those in your supplement program. I don't use coffee grounds either. They are weak in nutrient value and only add a little N to soils over time. Not a good trade, as they tend to fill air spaces in soils as they quickly break down. I am thinking of switching to a time-release, but not sure how much to throw into the batches of your mix. I don't remember the exact formula right now, but it's around 19-6-12 that I use initially. I probably use around 1/4 - 1/3 cup per cu ft of soil, but that is only insurance & won't last the whole season. I start a supplemental program almost immediately after building the planting. I began composting, and plan to use that in place of the cheap bagged potting soil ingredient. Of course, it's your soil, but compost adds little in the way of nutrients & tends to compact and settle into soil macro-pores. I never use it in containers. I've had many spirited discussions about the advisability of using it in containers. Most that argue for its use draw no delineation between garden culture and container culture. They figure that because it's good for gardens, it must be good for containers. You can see I disagree. The other common argument is "It works for me", which doesn't really convince me I should try to make it work too. You'll have to decide this for yourself. I wasn't too sure if I was running on a parallel track with you, or if I went astray somehow. If you have other questions, please voice them & I or another will help further, I'm sure. Good luck - take care Al

One thing we need to respect is another's perspective. One grower might look at growing with the attitude that nothing is going to stand in the way of my reducing the effects of every limiting factor that impact my plants' growth and vitality. Growers like this tend to look at growing from the plant's perspective. Another grower might not be interested in entertaining the thought of changing anything, so long as the plant seems to be doing well enough. I've found this to be especially true if the chance involves more effort or expense - this is more a view from the grower's perspective - how it affects ME, rather than the plant. Neither perspective is wrong, they're just different ways of looking at things and ordering priorities. We all go through the same considerations, but some people come down on the plant's side & others on the grower's side. A prime example of this can be seen in the form of people arguing vehemently against the effort involved in finding ingredients and then making either the 5:1:1 mix or gritty mix. Almost always, the argument against comes from growers who have never tried either mix, and are content with the results they get from a from-the-bag mix because it's easy. Not all of us orders our priorities in that fashion. My good enough may be her poor; and good may in fact not be good enough for her. I know a lot of people like that and admire them for their desire for continual improvement. Rachel's question is a very good one, and her commentary clearly illustrates she's been thinking the issue through (from the plant's perspective) and looking for some input. Any teacher would give her high marks for that. I say often that our plants are already genetically programmed to grow to be beautiful specimens. The ONLY thing we can do to help is to be proactive in continually reducing the effects of ALL things that have the potential to limit growth/vitality. Remember, if everything is perfect except ONE thing, that single limitation can wreck the entire growing experience. One thing for Rachel to consider is that water in plunged pots behaves differently than it does in conventional container culture. That they are partially buried turns them into mini raised beds, hydrologically speaking. As long as they are not plunged into clay, the earth will quickly wick any perched water from the soil she chooses; so she has roughly the same potential for growth/vitality using soils that would otherwise be too heavy (water retentive) to be well suited to container growing as she does if using the gritty mix or the 5:1:1 mix. Since there is little notable loss in potential, based on her growing method, if using a heavier soil, we need to look to the interval between when the pots are lifted and moved indoors and when they're returned to the garden or beds and buried. Normally, there would be considerable concern over accumulating salts during the over-wintering period; this, as a result of having to water a heavy soil in small sips to avoid the soil being wet for any extended period. Since I believe she will be watering rather infrequently, it may not be a serious issue. Just a guess - if she's watering less often than every two weeks, I think she should be ok until repot time. Also, if she's willing to cheat the state out of a little rain water and use that to water with, it pretty much makes it a nonissue. I think Rachel's free to use a heavier soil if she wants to, and it shouldn't have any notable effect on her plants. If she has a suitable bark on hand - maybe something like a 5:2or3:1 bark:peat:perlite would be good - or even a bagged soil. The only real disadvantage to a peaty soil for this particular application is that it makes repotting more difficult. So - there's a little about perspectives and growing for you to consider. I hope there's enough there for you to set course with a little greater degree of certainty. Time to get out in the yard before it gets too hot again. It looks like another day that will be pushing 100*. Take care - thanks for the kind words. ;-) Al