I would agree with Rhizo and Calistoga... this is the base of your business, the root of it so to speak, and if you want to build a good reputation for producing and selling a good, healthy product, you ultimately have to spend a little in order to make it all come together as you want it to. I would recommend doing some reading and research before embarking upon your venture. "Container Soils - Water Movement & Retention XVII" is a great place to begin. You can usually find this article on the first page of this forum. Container growing is vastly different than growing in a garden, so you'll want to address the needs of plants specifically grown in containers. Poor soil can make or break you as a nursery. When I buy plants from any source, or am mixing my own mediums, my preference is a fir bark based, gritty, larger particled, fast draining medium that won't hold a perched water table, and won't require re-potting on a yearly basis, which ultimately saves money, labor, and time. Save the organic methods for the garden... go for a more inorganic approach to container growing. You want to control what happens within those containers, including moisture, plant nutrition, light, etc... it's best to have your information firmly in hand before you begin this sort of business, or you'll fail before you ever get going. I run a small niche business selling plants, and before I begun, I made sure I had a business plan, and I made sure I knew what I was doing... from the soil up. You really don't want to flounder around without an understanding of plants or their requirements, from a more scientific angle. Tapla's article will help you get there, I believe. It helped me more than I can say. A green thumb is nothing more than applied knowledge. Happy Growing!

It wouldn't be unusual to be doing things right & still have chlorotic plants. My tap-water runs from about 8.5-8.8. depending on the time of year, and I need to acidify or use Sprint 138 to make sure they get the Fe they need - especially in the winter, when I can't flush the containers as copiously. You prolly want to use citric or sulfuric acid for that many containers (never add water to H2SO4 - add the H2SO4 to water - or just go for the citric acid to be safe). Draw a given amount of fresh water, and add enough acidifying agent to bring the pH down to 5.0-5.5 for most plants, or to your target pH. Make note of how much it took, then, when you water or fertigate, add that much to the same volume of water. Check from time to time to make sure you're on target. If 5.0-5.5 seems lower than you expect, it's because plants do better in container media at about a full number lower than in mineral soils, AND, the pH of freshly drawn water will rise as the dissolved CO2 in it gases off. Al

I try to write pretty precisely. I wrote "the posts I have seen in the past on the 'hydraulics' of drainage in pots" intentionally, to get away from the specific article you referenced as I didn't have time or inclination to go through it right then. The posts I refer to were related in topic and on Gardenweb but in another forum (I forget which). They invoked a zone of saturation perched in the finer soil just above the bottom coarser material. That made no sense to me hydrologically. I (back then) briefly looked at what professional soils hydrology (soils physics) literature had to say about it and saw that it was not in fact any true perching of saturation, especially not likely long enough to do any harm to roots, but was merely a delay in the downward passage of the pressure wave (relates to percentage of saturation). And if I recall correctly (it's been a while), the only time you got saturation at all above the textural boundary is when the finer soil is very fine and is capable of holding saturation there by capillary tension. Clays or fine silts are not what we want as potting soil in any event. The possible definitional problem I referred to was the probability of horticulturists defining perching or an elevated zone of saturation differently than a soils physicists would, even if both were agronomists. A ground water hydrologist would look at it still differently. A soils physicist would tend to look at perching as saturation in a steady state (stable except for evapotranspiration); a horticulturist or orchardist or farmer would look at it as perched if it stayed there long enough to do some harm (or good); a ground water hydrologist would not pay much attention to it unless it lasted for months or years (except possibly in terms of inducing lateral flow in recharge events). Here, I again refer to those earlier posts: I think the notion that coarser material at the bottom of a pot is in any way harmful in terms of drainage IS a horticultural myth. The point may be well taken that the older notion of its necessity may be a myth too.

Thanks. This is interesting. The consumer containers I'm used to have one or two holes about 1/4" wide (like a pencil was pushed through) on bottom - minimal chance for media loss. Most of the nursery pots I've purchased have multiple holes over 3/4" in diameter. One deeper type has 3"x1" openings slashed across the bottom. Super for drainage, but not the easiest to retain, say, a GW Container-Forum style "gritty" mix. But nursery pots are so inexpensive, they are worth any extra effort. Here are links to pics of couple I've actually purchased: N. Pot 1 Deep Pot 1 N. Pot 2