amending soil

Ok I sort of asked this question on another thread but let me if I may re phrase the question. I tested my soil in my iris bed. It had a ph of about 8.0. I have both tb and siberians planted there. I tested the bed into which I had planned to move the siberians. It's not much different.
As I understand it I need to lower that number a bit. I read somewhere that I could put rock sulphur (?) in the soil (mine being a bit sandy) and that would lower it about a point??? Is that correct?

Does anyone else have any suggestions? Should I just leave the siberians and work on the new bed and transplant next spring? What should I do?

Anne

I had my soil tested this year and it turned out that my soil is a bit too alkaline for Sibs, as well. According to information on the Society for Siberian Irises website, the ideal soil pH for Sibs is in the range of 6.0-7.0.

I received an instruction sheet with my soil test results that provided the following information. I have to reformat it because I can't copy and paste the chart as it appears on the instruction sheet.

"Materials and amounts required to decrease the soil pH by one pH unit." [in other words, reducing it from 8.0 to 7.0]

All of these values refer to lbs/1000sq. ft. of garden space and are listed according to your soil texture (coarse, medium, or fine/peat).

"Aluminum Sulfate - coarse 2.5 lbs/1000sq. ft., medium 5.0 lbs/1000sq. ft., fine/peat 7.0 lbs/1000sq. ft.

Iron Sulfate - coarse 2.5 lbs/1000sq. ft., medium 5.0 lbs/1000sq. ft., fine/peat 7.0 lbs/1000sq. ft.

Sulfur, finely ground - coarse 0.5 lbs/1000sq. ft., medium 1.0 lbs/1000sq. ft., fine/peat 1.5 lbs/1000sq. ft.

The ground sulfur reacts slowly (3 to 6 months). For faster pH reduction, the iron sulfate is commonly used."

Of course you would only use ONE of these materials to lower your soil pH, not all three. You can also lower soil pH by tilling in pine needles and/or sphagnum peat moss, though I don't know how much you'd have to use or how much they would lower the pH or how quickly they would lower it or how long the lowered pH would last before retreatment would be required.

Hope that helps.

Laurie

Pine needles would be a cinch around here. Thanks I'll give it a shot.

Pine needles are not very useful compared to to the compounds mentioned, and less pH lowering than sphagnum moss too. Once you get the pH to where you need it, it will probably still begin to creep back to its original pH in time. (And what is the pH of the water that you'd be watering with? Probably high.) I'd use the pine needles for added organic matter, and to keep the pH stablized after your initial pH balancing. Pine needles are excellent for these applications. Compost (including pine needle compost) is great for buffering, and keeping mad swings in soil pH from happening. I would guess though, that undecomposed pine needles would have a greater effect for lowering pH than composted.

Just to make sure no one gets the wrong idea, since the pH scale is logarithmic, remember this can't be accurate for the entire pH scale. For every point away from neutral, the change must be ten times that of the previous. So:
.....
-- From pH 9 to pH 8 requires 10X amount of acidity.
-- From pH 8 to pH 7 requires X amount of acidity.
-- From pH 7 to pH 6 requires X amount of acidity.
-- From pH 6 to pH 5 requires 10X amount of acidity.
-- From pH 5 to pH 4 requires 100X amount of acidity.
etc.
(From 8 to 7 and 7 to 6, X is the same since pH 7 is neutral.)

I suspect the pH change they are talking about is specific to Laurie's soil pH, and thus similarly to yours also.

Thanks for the information, Leftwood.

From the great expanse where I garden, under very old pines, and the variety of plants (including hydrangeas that stay pink and others that stay blue) along with hundreds of daylilies, peonies, hosta, astilbe, polygonatum, Siberian/Japanese and tall bearded irises, I know the pine needles can't have any real effect on the PH of the soil or something would show it.

In the meantime, until you do move your siberians, watering with Miracid every two weeks does help.

Great advice above! Pine needles will not lower the soil ph much, but they sure are good for compost, and for mulching. And what Leftwood said about compost being great for buffering is so true. Compost is wonderful.

How big an area do you plan on amending?

Schreiners says the best ph for bearded is 6.8. Siberians would do well at that level also.

How long have you had your irises in the bed, and how are they doing currently?

I water my JIs with vinegar and water. They seem to like it. I use a watering can and put about 1/2 cup vinegar to 4 gal. watering can. This is often added to alfalfa/manure tea and sometimes some epsom salts as well.

Inanda - busily covering rhz. with sand for the winter

The bed itself is fairly new (within last 4 months). And the irises both tb and sib. aren't faring well. I need to do something quickly. The space that I will start with is under an oak tree and transplant 4 or 5 out of the original 9 that I had. I'm thinking that I will till in fresh pine needles and then water with miracid (?). Does this sound like a good solution?

Anne

I wouldn't plant Sibs under any tree. Sibs like lots of soil moisture, and trees are moisture hogs. I doubt if Sibs could compete successfully with tree roots for available soil moisture.

Also, according to Leftwood's and Polly's posts, pine needles won't do much to lower your soil pH, and Miracid is only a very temporary fix. You'd be better off applying iron sulfate if you want to lower your pH quickly and keep it lowered for a significant period of time.

Laurie

This advice is for the siberians only. Laurie can give you better advice on the bearded, that I'm not familiar with.

Miracid is only a temporary fix, but I would get some and use it now. Siberians decline rather quickly in an alkaline soil. Make sure you water them thoroughly with the Miracid, and that it gets the foliage wet. The Miracid is not going to hurt them, no matter what soil you put them into. I would do it right now, while you're deciding what to do with them.

Personally, with the soil as high ph as yours, I would add iron sulfate as Laurie states, and amend the soil with peat moss, and compost. But in the meantime get some Miracid on the sibs.

Also keep the siberian iris well watered. If you are going to plant them under a tree, make sure you will be able to water them at least 2X per week, watering deeply all year round. The trees roots will take the water away from them.

As for planting under a tree, the side in which I plan to plant them gets afternoon sun so being a moisture bog isn't an issue here. I propose the tree, in part because of the way I am. The irises are now in a part of the yard that I have to make a special trip to and the tree is in a line with where I regularly have to water. So the chances of their getting watered on a regular basis is much better under the tree. And I'm on my way out and will get the miracid while I'm out. Thank you so much for the advice. Any other thoughts will be greatly appreciated.

Well then, hopefully sun won't be much of a problem, but you will still need to water just as if the iris were under the tree. Tree roots can easily reach out 1.5-2 times the height of the tree. Not that you don't have a solution, but just so you know what you will be dealing with.

Went this afternoon and purchased a small bag of rock sulphur and brought home a couple of bags of pine needles as well. I didn't have time to till but I will try to do that some time thru the week. I haven't been able to find any miracid. Will keep looking.

HD sells a fertilizer for azales, hollies and rhododendrons. I'll try to remember to look at the package to give you the name of it.

May I plead blonde?

I went to the garage, camera in hand, only to see it is Miracle Gro food for azaleas, etc. Boy, do I ever feel dumb.

Looking back at AuntAnne's post, my box isn't labeled Mir Acid. I remember that in a silvery box but this is a blue box.

Here we go!

lol that's ok. I'm still trying to figure out who in the heck I sent the Trop hib cuttings to, since they didn't get to where they were supposed to go to. lol I didn't get a chance to get to HD or Lowes but will later this week.

Anne

What Pirl has is the same as Miracid, just new packaging (I think). Anyway, it will do just as well, even if it's not the same formulation. Anne, just look for a fertilizer you can spray on that is for azaleas and rhododendrons. The best thing to do is get it on the leaves at this point, so you don't want anything not water soluble.

K, I will try to get by HD or Lowes this week. Thank you so much for the help. I just never paid attention to why things didn't grow for me, until I started coming to this site. It's a little more complicated than just sticking them in the ground. Funny though my mom planted some purple flags 16 yrs ago, before her death in '92 and they just lived on with absolutely no care by dad. I divided them earlier this year but have done nothing other than that. I'm guessing that is the difference between the types.

Anne

Long ago I don't think feeding plants was looked on as being necessary. Yes, folks would make up manure tea for the roses or feed old nails to a hydrangea but now, with the variety of foods, and the knowledge of how much better plants can perform given the right treatment, we have everything available to get the best possible performance from our plants.

Polly is right, what Pirl has is the same as Mir-acid. They don't make the Mir-acid named product anymore. I work at HD, and talked extensively about the stupid change with the vendor reps. None of them could give me a concrete answer why the name was dropped (and the trademark silver and blue box), but they all tell me the Azalea, Camellia and Rhododendron fertilizer is the same.

I didn't even look at the numbers and I'm too tired now to do anything but sleep. I'll be using it tomorrow so I'll try and get back here to post the numbers. It would help to know what the numbers NPK were on Mir Acid. I doubt I have any of it left.

k, good info to have. It's going to be Thurs before I can get anything.

Aha! Mir-Acid was 30-10-30 and the new box is 30-10-10!

I still have an old Mir-acid silve/blue box. It says 30-10-10, not 30-10-30. Don't know where you got your info, but I have living proof.

Either Google did it or I didn't have my glasses on. Glad to know it's the same. Thank you for reporting.