Home made soil mixes, high pH

Does anyone have a formula for a potting mix that is low in peat? I thought that this year I would try to cater more to the soil needs of some of the plants that I grow that prefer a high pH--things like Phlox, Sweet Peas, regular peas, brassicas, etc.

(and does anyone else have an on-going problem with getting their heads around the fact that low peat=high pH and vice versa? Drives me crazy--every year I have to look it up.)

Peat is acidic (Low PH)
Lime is alkaline (High PH) and is often added to peat in order to raise its PH as it is very acidic.

Milan

Thanks Milan...yes, I know about using lime to raise the pH but it is very slow-acting, and I don't think it would be suitable for potting or seeding mixes. Any other thoughts about something more immediate?

Actually pulverized lime raises the soil PH very fast and is pretty much the best method around. Soils rich in decomposing organic matter require more lime and frequent reapplication of lime to keep the PH up as active decomposition gives of humic acid which in turn re-acidifies the soil.

Milan

Thanks, Milan.

I've just the ordinary dolomite lime--small granules--would crushing it further be a good idea? Any idea how much to use? I add a bit of lime, plus bone meal, blood meal and wood ash when I make up my usual mix and end up with a pH of around 6.5. I'd like to try for higher..would you suggest keeping my same peat/compost/perlite ratio and adding more lime?.

The commercially available granules usually disolve fast and should not require further crushing.
Sure add more lime to your mix if you want a higher PH but I can't give you a "rule of thumb" on how much to use. You gotta do it by trial and error. Hope you've got an electronic PH meter :).

Milan

Well, trial & error is my middle name...lots of trials, lots of errors. Was being lazy looking for the magic bullet! I'll just throw a bit more lime than usual into my mix for the high pH guys and see if it makes a difference.

Guess I'll put electronic pH meter on my birthday wish list. I do have a test kit, but that sounds like more fun..

Chilko, I was noticing some hydroponic pH Up and pH Down in Rona yesterday. As this is in liquid form, it would cause immediate shift. So...if you're into experimentation and get your pH meter, you might want to go out on a limb so to speak to figure out how much to how much. And if you are so daring, please post results.

Sounds like just what I want! Thanks for the idea.

Rona here (Williams Lake) doesn't usually get garden stuff until around Mother's Day, but I'll check for it anyhow when I do my semi-annual shopping trip. That will be as soon as we can drive out of here, mid to late April.

Wonder if you could use the product they sell for hot tubs/spas? if you can't find the other stuff.

What a good idea--I have some of that on hand. Will have to check to see if it is safe for plants (but if it ISN'T, maybe we shouldn't us it either!)

Somebody was going to tell me what was in that stuff. I will have to see if I can find him.

PH up for Hydroponics usually contain Potassium Hydroxide or Potassium Carbonate. Upping pool PH is often done with Borax or Sodium Bicarbonate (yes good old Baking Soda). I recommend against the use of commercially available Pool PH products for your plants as there might be additives in there that may not be taken well by your plants (Algicides, chlorine stabalizers,...). You can try the Hydroponic PH control but be advised that these are formulated for nutrient solutions used on soil less mediums and not direct soil use. Though they may change the soil PH quickly, they may not be able to maintain the PH level for long. Plants "hate" fluctuating PH much more than a less than ideal PH. On the other side it may work well so give it a try, just observe closely :).

Milan

How about the spa chemicals, thought they were a bit different from the pool chemicals because of the heat? I've always had to buy chlorine (or here its been bromine) stabilizer separate. Have seen the algicides, but don't think they are commonly used with spas. Ours is always covered. If I can just use baking soda, that would be great.

Changing the PH in water quickly is easy but maintaining the PH without having to constantly readjust it can be difficult.
My PH knowhow mostly comes from freshwater and saltwater aquariums where it can be very challenging to maintain a stable PH without killing all the inahabitants in the process :). It's been a long time when I was deeply involved with the chemical interactions but luckily the internet is there to refresh my memory on the things I can't remember anymore LOL.
Personally I would say that spa chemicals shouldn't be different from pool chemicals but then again who knows what they mix in there. If you get out of the spa and your skin doesn't peel off then your chemicals in there should be good right? :)

Jury's still out?

I wonder then if I can add borax to my potting mix, to raise the pH? Any guess as to how much?

Chilko,

I realize this may be many months too late, but your idea of adding borax to your potting mix to raise the pH is not a good idea.

Boron is a needed trace element, but it doesn't take much of it to reach toxic levels. Some trace element formulas omit boron in case your water supply and/or your garden soil already contain boron.

MM

Hey, MM

Thanks for warning about the borax. Just got back on DG after a very long absence. As it turned out, my world imploded late March and I wasn't able to do much of anything garden-wise beyond the absolute basics--am now compiling info for NEXT year.

Always next year, right?

One of the real negatives for me was using a Sunshine formulation instead of making my own potting soil. Most of my bedding plants and veggie starts languished and many died before I realized the problem...the bales I'd been sold for starting mix were actually intended for low feed requirement plants and any fertilizer in it washed through after the first few waterings. My plants literally starved.

That will teach me not to take clerk's advice and to do my own research!

Welcome back. Hope your life has straightened out. Wondered where you had been.

Nice to see you back, Rosemary. We've missed you.