If I'm not mistaken, gypsum is used in lieu of lime when you want to supply calcium but not raise the pH of the mix. When I use gypsum, I also need to make sure that I somehow add magnesium since lime supplies calcium and magnesium. Epsom salts is a good source of magnesium.

Gypsum + epsom salt is only necessary if your water and fertilizer are lacking in Ca and Mg. Dyna-Gro's Foliage Pro 9-3-6 is a very popular fertilizer choice around here, and it contains Ca and Mg which makes gypsum and epsom salt unnecessary.

-Chris

BTW, your granite and DE look good, but the bark appears to have some shredded material which may be sapwood rather than bark. If so, it will quickly break down reducing porosity and absorbing nitrogen. You may want to take a closer look or post a close-up photo.

-Chris

Your replies are very helpful, thank you. I do plan on using the Foliage Pro liquid. My very hard water has no lack of Ca or Mg anyway, but that's good to know.

Looking at this picture Chris, the shredded part does have longitudinal grain (cambium layer?) as compared to the chunky pieces that are obviously bark. There is some of this in the bag, but I could probably sort most of it out. I could also get repti bark if that would be better.

It looks like it could work if you're willing to pick out most of the woody bits. Repti-bark is very easy to use since it typically requires no sifting or picking, but you pay for that convenience. I've started using an orchid bark that costs more than I'd like, but it's cheaper than Repti-bark, and I only pick out the occasional bit of sapwood.

Here's some gritty mix I recently made with perlite in place of granite.

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-Chris

The perlite would definitely make the mix lighter which would be a plus to me. What are the pros and cons of using perlite in place of granite, other than the weight factor? Could you do half and half perlite with granite for the one part granite fraction?

Perlite tends to float, so over time the mix might not stay as "homogenous" as it would with the granite

Thank you howelbama, that makes sense.

When it comes time to re-pot, what should be done with the used material? I'm concerned that the DE will interfere with the soil organisms in my garden if I add it to the compost. I don't want to throw it in the trash. Any advice on that point? How long does the mix last?

I really would prefer to use turface rather than DE, but haven't found it available locally. I know there is a precaution to protect against breathing the dust when doing the fine screening. It would be easier to use turface, if I could get it.

Some people submerge the old mix in a water bath and allow the bark fines to float off, then replace that portion with fresh bark and reuse the rest. The mix should last at least three years, maybe more.

If you have a John Deere landscape supply nearby, they will have the turface. Or you could try contacting a local little league organization and see where they get theirs for the ball fields.

I substituted perlite in my mix to cut down the weight, and it is much lighter this way. It's working very well so far and I haven't noticed any separation when watering gently. But I don't think I would use this mix outdoors. The wind and rain could send the perlite everywhere and possibly knock over or uproot top heavy plants.

As for Floor Dry, I've used it and it seems to be a perfectly acceptable substitute for Turface. I prefer the color of Turface though, and since they're about the same price, I use Turface. Their website lists distributors for each state. That's how I found mine.

Also, I don't think calcined DE like Floor Dry will be a problem for soil microorganisms. It's powdered DE that is used to control pests.

-Chris

Thanks for the tip re: John Deere Landscape supply. I do have one reasonably close.

Is there much difference in the water holding capacity of turface vs. the DE product?

Here is my first subject, a little succulent that looks kinda sick to me. I potted it up last night and watered; it's already completely dry (I live in Phoenix and it's June, after all). Is it going to be a problem if I put my citrus tree in this mix? Of course the citrus is in a larger pot. The leaves on the citrus are cupping a bit, which I think may be from too much water held in the soil.

I believe the napa product is more porous than the turface, so it will probably hold on to the fertilizer and moisture a bit more. I believe many people in the forum use both with pretty much equal success.

I'm not 100% sure on repotting the citrus now, but I believe it would be better to wait until the tree is not in a heavy period of growth. If the mix it is in now is holding too much moisture and has a high perched water table, you may be able to drill a hole in the base and work a nylon wick in to the soil somehow. This may help to reduce the pwc for the time being until a repot would be ideal. I don't grow citrus, so hopefully tapla's or someone with experience can advice the best time to do your repot.

When you first start using it, I highly suggest using a wooden stick of sorts - I use a wooden skewer - to test how wet it is, or isn't. It holds more water than I realized; the top may be dry to the touch, but an inch or so down, it may be quite damp.

I put the skewer in for a few moments, take it out, and set it on my wrist or hand. You can tell easily if it's outright wet, damp, cool, or dry. Cool may mean time to water, depending on the plant.

howelbama, thanks for your recommendation to wait to repot my lime tree. I have put a wick in there. It's dry but the soil is still moist. I think the mix has way too much coir or something, it's very retentive. It should make it until fall. I was told to wait until the tree is rootbound before repotting but if the soil is too soggy, wouldn't it be better to change it?

lathyrus odoratus, thanks for the tip on the stick. I have some cake testers that would be perfect for these little pots.

Haname,

I think it's usually best to wait for a tree to enter dormancy and to repot just before it breaks dormancy, but I'm not sure what a citrus tree dormancy period is. You may be right that in your case a repot would be appropriate now... However, I am hoping that the master of repotting/all things containerized lol, tapla, will chime in and help you out... Or possibly one of the other folks on the forum that have specific experience growing citrus in containers.

I would hold off for now and wait to see if someone else jumps in with more advice.

Haname, great information here so far.
With Citrus, Spring re-potting is best, between flushes of growth. In my area, that means sometime
in April. In Arizona, I would assume a bit earlier - March/April?

Also, after re-potting, it speeds recovery if you put the plant in a protected, shady location.
With Citrus, I typically protect the plant from intense sun and wind for about two weeks.

Josh

Thanks howelbama and greenman, I will take the advice to wait until spring. Meanwhile, I will take care not to water the tree until it begins to dry out.

My succulent is in a protected, shady area. I take it we should look for new growth as an indicator that the plant has recovered?

Re: Foliage Pro, generally speaking, is it best to wait on feeding until after a plant is showing signs of growth?