Soil porosity values are well documented and can even be calculated from the various particle sizes in the soil. Published values (percent air space within the soil) range from about 40%-60%, usually very close to 50%. This holds all the way to pure sand and even larger solid materials, as shown by your gravel result. Your value of 30% is anomolously low, perhaps because there was a small amount of water already present, perhaps experimental error (since the water capacity was measured at 35%, physically impossible to be more than the porosity). Published values for the water holding capacity are generally about 10% lower than the total porosity for mineral soils. The value of 35% for your soil is actually at the low end (again there may have been 5%-10% moisture already in the soil), with values up to 50% for heavy soils being quite common. Sand, and fine gravels, are much lower, around the 25% value you show for gravel. They don't describe peat as "fluffy" for nothing ;) One of the problems with peat is the very large difference between the amount of water retained from a dynamic watering, and the maximum amount of water which can be soaked up, for example from standing in a saucer. This is what you referred to as wettability in another thread. Although peat retains air from a simple watering, it can become almost fully saturated from being allowed t soak up water. You can measure this by a third experiment where the cup is allowed to stand in water for a few hours. I believe that the same thing applies to the calcined clays like Turface although I can't find any published experiments on this. It is certainly a valuable property in a soil because, as we discussed on the other thread, it will often reduce or eliminate a perched water table after a pot has been watered from above. Perlite does not show this property because it is a closed cell granule. The air pockets within each particle are not open to the exterior in any way. This shows in the very low saturation number you found and is also apparent in the willingness to float. Volcanic rocks are very variable, some closed cell, some open, and the cell size and base density of the rock varies. Yours shows the properties of a closed cell rock, or perhaps it is simply a very coarse rock with large internal cells. Of course it still remains to discuss what ideal values of these properties might be in a succulent container soil. Total porosity is often mentioned and it is claimed that it should be 60%-70%, certainly never below 50%. I feel that this isn't the most important number, rather that the air space remaining after you water is critical for succulents, as indicated by the lower saturation numbers in your table. I suspect that rather dense soils are valuable for many succulents, certainly Lithops and some cacti seem to prefer a soil which would have low total porosity. Others prefer a much higher porosity, I would suggest that fleshy rooted species like Ectotropis, Haworthias, and some cacti, prefer a especially open soil (although possibly require regular watering in such a soil). Lastly I still claim that the wettability, or lack of it, is important, possibly more important than any of the measurements here. In your experiment where tipping a pot forces extra water to drain, when tipping the pot a few minutes later does not force extra water to drain the perched water table has been eliminated and this is a good thing. There are other ways to quickly reduce or eliminate perched water tables: porous clay pots; only watering in dry sunny weather; and only watering plants which are thirsty. On the other hand, some growers habitually water from below, I don't know whether this overrides any wettability issues to force a perched water table or actually reduces the amount of water retained within the soil because of limited capillary action or limited time standing in the water. Presumably all these things are possible and each grower has adapted a method which suits their own soil mixes and plants. My experience is that bottom watering is a way to put extra water into the soil and I only use occasionally for plants which are in peak growth or subject to very drying conditions (my soil and pots are chosen for safety in a cool humid climate and dry exceptionally quickly by in rare hot low humidity conditions).

Thanks Jll..good job straddling that fence, but both sound look good advice! Dave, I love the idea of a greenhouse! I am impulsive enough to go out and build one tomorrow, but the question that immediately came to my mind was...do I really need a greenhouse in San Diego, with our cold season so short? If the answer is yes, and I can learn how to properly use one..well then sign me up! In the meantime, I'm probably going to have to do one of the two options that you both laid out. I'm going to cover them tonight, since we're dipping below 40. I don't know if there is a way to find out what the probability of a rainy vs dry season for this spring will be. Farmer's Almanac perhaps? I really have no clue there. Since I don't have other containers on hand, I think I may go the route of planting them and ensuring that they are covered in cold temps. One last question since we're on the tomato topic here: I just planted some heirloom tomato seeds and they are indoors at the moment. I think I may have planted them too deep. They were tiny seeds, and I probably planted them an inch deep, perhaps a bit more. Will those come up? I'm tempted to just add another seed very shallow to those peat pots, as I read that seeds should be planted at a depth approx half their circumference. That would make these just barely below the surface. Is that correct? I am already having so much fun and look forward to learning and sharing with everyone on the forum!

Wow. So generous of you to post this-- I wish everyone did this after 4 years! It's quite different than "I've had this for a month and love it!" Very useful information indeed.

I second pillog's recommendation for a test drive, especially if you can go to Purcell Murray. Amazing places for an appliance geek (My SoCal cousins tell me there is now one in Huntington Beach now in addition to the one that I went to in Brisbane some years ago when I was last on that coast.) Getting hands on time -- cleaning up as well as cooking --- is, as they say, priceless. Not everybody likes induction, but most who try it find that they like it a lot. To be sure, you and your wife might still find that you prefer one or more particular gas cooktops over the specific induction units you try, but, as pillog says, you won't know for sure until you try them out. I say this as somebody who likes induction a lot --- I've used induction at various times over the last thirty years --- but nonetheless ended up choosing a particual gas range over the two induction stoves I was looking at when I was last stove shopping. I "get" your wife's preferences for seeing flames while cooking and for having a stove that is simple enough for me to maintain and repair by myslef. I, too, prefer rotary knobs on stoves to digital touchpads, (Unlike some, I'm not opposed to touchpads. After all, I make my living in digital media production. Still, when it comes to stoves, I'm happier turning large knobs.) But those are only a few of many factors which can affect how well or poorly a stove or cooktop will serve you in your cooking in your kitchen. Every appliance is a mix of attributes and design compomises. You choose a balance that you think may suit you better than another.What I found when I was shopping -- wow, almost three years ago --- was that the balance of factors slightly favored this one particular gas range over the two specific induction ranges I was looking at. Were I shopping today, I would still consider my gas range but the newer models of induction ranges are now available and the balance (for me) might very tip to one of them, instead. For me, it would really help to lay hands on the actual equipment and get a test drive. Hands on time will likely tell you and you wife more than reams of further commentary here. So, if you can get the opportunity, take it. And, to go back to one of your original questions about safety features, the boil-over shut-downs work a bit differently on different models and brands. There is a thread currently on chowhound with some discussion of this subject. Apparently, some folks (with JennAir models, IIRC) find it over-sensitive and annoying to them. Others, with different models, report experiences in line with what Gary reported. (I've never had problems with it myself, either.) Here's the link if you want to plow through another induction thread. http://chowhound.chow.com/topics/903217 This post was edited by JWVideo on Thu, Mar 27, 14 at 21:05