I wouldn't use the oyster shells or anything dusty. The gritty mix works so well because at least 2/3 of the particles are in the perfect size range that allows them to hold good amounts of water (and the nutrients in the water) without holding any 'perched water'. This practically eliminates over-watering error AND allows you to water copiously at EVERY watering, which prevents long term build-up of soluble salts in the soil. This adds even more value when it's used with plants that won't tolerate wet feet (succulents, cacti, others) - plants you're usually tempted to water in sips, contributing to salt accumulation.

I noticed you live in Canada, so I don't know if Gran-I-Grit is available there. Often, when I'm trying to help a person that showed up on the forums or in my email, I find out where they live & then call an officer of the nearest bonsai club for the lowdown on what they use locally and where they buy it. You could do the same. Try a swimming pool supply place company for the large silica. It's used in filters. Or try a masonry supply store - a real one, not a big box store. The silica can be used instead of the grit (you really don't need both) if it's large enough (1/2 BB size to BB size is best.

Fir and pine bark are interchangeable. You want uncomposted product for the gritty mix and (if you can find it) partially composted for the 5:1:1 mix.

The main elements you need to worry about supplying when using the gritty mix are are NPK, Ca, Mg, Fe, Z, Mn, S. The rest are unlikely to be deficient. Your MG supplies NPK, Fe, Mn, and Z. The gypsum will supply Ca and S. That leaves only Mg to worry about, which you will supply my adding a small amt of MgSO4 (Epsom salts) to your fertilizer solution every time you fertilize. I still use STEM or Micromax though - to be sure all the bases are covered. You could probably order some Dyna-Gro Microblast if you wanted to be absolutely sure.

Al

Hi Al,

First, thank you for being so generous with your knowledge and for taking the time to answer all those questions posed by not only myself, but others on these forums. I have read countless posts with great interest and your thorough answers have taught me so much.

So I took your comment of "a real one, not a big box store" from above and applied it to my search for turkey grit. Turns out that if I leave the city and go into the nearest farming community, there are REAL feed stores. And not surprisingly, they have all sorts of grit! So for $7, I came home with 50lbs of 1/4" crushed granite grit.

Having chopped the 1" pine nuggets down using our kitchen blender and learning, amongst other things, to screen the ingredients before rinsing to remove the dust I now have what I think is the final succulent mix that I've been hoping for. Now all I need to do is repot my sad looking succulents and cacti plants.

{{gwi:9681}}

Thanks so much, I look forward to seeing the results!

Bob

I feel bad for having to tell you this, but the grit & Turface should be in the 1/8 and smaller size. The bark can be a little larger w/o too much change in drainage/water retention. You can use the soil as is (you'll have to water quite often) or add another part or two of screened Turface or calcined DE. It looks like the grit you got is 'developer/layer' size & what you wanted was 'grower' size.

Do you have the nutrition down? You're going to use gypsum, add Epsom salts to the fertilizer solution, and use a 3:1:2 ratio fertilizer?

Al

I had a feeling that I might have chosen the wrong one. The feed store had 3 or 4 other sizes as well so when I saw the grower size 1/16" - 1/8" I thought that it looked a little small. Not a problem though ... the feed store has 50ib bags of seed potatoes for $15 so in a few weeks I'll be going back anyway.

Do I need the same 1/8" size when it comes to the perlite in the 5:1:1 mix?

I added the tiny little balls of gypsum (1 tbsp) to the mix as the recipe calls for as well as the 1 cup of vermiculite.

For nutrition, I have the Miracle-Gro 24-8-16 water soluable plant food with micronutrients which I will mix half strength and add 3 tbsp Epsom salts and 2 tbsp STEM. Since the Miracle-Gro has iron I don't think I need to add the 7% iron chelate, though correct me if I'm wrong.

Bob

I use either medium or coarse perlite with no apparent difference in results.

The 'balls' of gypsum are actually 'prills'. They make a slurry of gypsum powder & a binder, then shoot it from a prilling tower. It forms tiny spheres called prills as it falls. The little balls will quickly dissolve.

If you're mixing the 24-8-16 @ 1/2 strength, you only use 1/8 tsp per gallon of fertilizer solution of Epsom salts and STEM each time you fertilize. I'm not sure where you came up with the 3 & 5 Tbsps. If added to a gallon of water along with the fertilizer, that would assuredly kill the plants. You need to be very cautious about micronutrients because the range between deficiency and toxicity levels is much narrower than it is for the macros and secondary macros. You're better off to not use STEM and rely on the MG and soil to supply everything than you are to overuse the STEM.

Al

Sorry, I should have specified that I was referring to your recipe for the concentrate from the Fertilizer Program thread found here.

I'll just use the formula above, that way I won't need to store the concentrate. I'm still looking for the Dyna-Gro Microblast so until found, I'll just go ahead without.

I assume that watering weakly weekly is appropriate though since I used the wrong size of grit, perhaps every 4-5 days. Can I end up overwatering if using the succulent mix?

Bob

You prolly won't find it in a big box store or nursery/greenhouse op. A hydroponics store would likely have it or equal in stock. For an online source, try Home Harvest.com

I suppose you COULD end up over-watering ..... if you worked real hard at it. ;o) Use a wick sticking out of the drain when you first start out. Don't water unless the wick is dry & you'll be fine.

Al

Hi Al. Quick question.

I plan on doing the "weakly weekly" fertlizing regimen for my small container-grown conifers. When I use the 1/4 tsp of Epsom salt per gallon of water each week can/should I add the Epsom salt to the same water as the 1/4 strength MG granular 24-8-16 fertilizer or should the fertilizer and the Epsom salt be added at different times.

I wasn't sure if adding the Epsom salt to the fertilizer water would be a good idea or not.

Thanks

Dave

Same water as the fertilizer.

Al

Thanks Al!

One more question. If you overfertilize a plant (in my case small conifers) do the plants tend to grow with bent trunks? Sounds strange, but I noticed that several of my conifers have trunks that are bent at a 20 to 30 degree angle. they should be roughly straight but they are not.

Might be a dumb question but thought I'd ask anyway. =)

Thanks!

Dave

I spent a pleasant afternoon mixing up a trashcan full of gritty mix; it was like layering a parfait of grit and bark and then smooshing it all together. The new containers haven't arrived yet; I did repot a Heuchera. I have a new bag of organic fertilizer; I just sprinkled some on top before watering. Since most of the stuff I plan to grow will be herbs, I don't anticipate needing a lot of fertilizer; is that correct?

Dave - over-fertilizing might kill the terminal bud on your leader & cause the tree to make co-dominant leaders that aren't in line with the original trunk, but it shouldn't cause trunks to bend or lean.

Libby - Is what correct? If you're asking about the fertilizer you used - it depends on what it was. If you're asking about whether your plants will/won't need much fertilizer - they'll need an average amount, maybe a little less.

Al

Thanks Al. So far the terminal buds on the leader and everywhere look healthy. I was just curious since several of the trunks looked bent, almost like the trees were in a high wind situation. Other than that they look perfectly healthy. Very few brown needles, even after a rough winter.

The roots look great as mentioned previously.

Thanks Al!

Dave