It could be soil moisture. The only way to really know is to dig down and check the moisture. If you have basically a hole full of peat moss, it's a pretty good possibility.

Hello...where are you located stb? Northern blueberries won't do well in the south. High bush wild blueberries grow in swamps here in Maine so I doubt if they are getting too much water. Check the PH of the soil...or better still have it done through the county agent...and also talk to him/her about what type of fertilizer to use and when...and take a picture of your plants and show it to the agent. Franklin

Much to the thoughts of some, peat moss is not all that acidic. While it is suggested to be part of any soil that is given to acidic plants, it is still not an amendment that changes the pH to any great degree that might cause a problem.
Many plants start out life in 50% peat moss.

Since blueberries do appreciate a noticeable acidic nature to its soil with a pH of 4.0 - 5.0, peat moss will not appreciably change it.

I agree, a soil test should give you the assurances you are doing right by your fruit.

Oh, I don't know about that. If you run a saturation extract on sphagnum peat, the leachate (which would be your soil solution if you were growing in straight peat) is going to run you right around 5.0, maybe a little lower. How much it changes a soil pH depends on a lot of stuff. Just for example, calcareous clay to peat at a 70% clay to 30% peat....meh not a huge change. Loamy sand to peat moss at as little as 80% sand to 20% peat, you'll see the pH move.

To a 4 x 4 plot I added one 3.8 cubic foot bale of peat moss because I wanted to drop the soil pH from 5.7 to 5.0 or maybe lower and a soil test one year later found that the soil pH in that plot was now 7.2. So does peat moss actually lower soil pH or not?
Around me Blueberries self seed on hummocks (small raised areas) next to standing water and they grow and blossom and produce prodigous quantities of berries, so I gather that while Blueberries do not want their roots in standing water they want lots of water close by. Most often I see, and the Blueberry growers around here tell me, that lack of sufficient soil moisture is the problem.

Like I was saying before, a lot of things factor into whether or not you get a big change from peat. But I can say this with confidence. If you measured an acid pH in the soil, added peat and then measured the soil pH as alkaline, something went haywire. Either something else was pushing the pH up, there was a sampling error (or two), or there was an analytical error (or two). It may have even been a combination of two or more of those things. Anecdotal evidence is funny that way.

And just to mention it. Sphagnum peat is more acidic than hypnum peat. But even hypnum is going to be neutral to slightly acidic and would not push a 5.7 up to a 7.2 on its own --not even if you were dealing with a low-organic sandy soil.

I would definitely check your PH. I started some blueberries this spring in some pots and all was well and they were very happy then out of the blue they started to turn brown. I checked the ph and it was so low the meter wouldn't read it. Come to find out the small amount of stuff I used to lower the PH from 7.5 to where I needed it went nuts and it took almost 3 months for it to take full effect and it dropped it so fast. I tried to save my plants but I think I only saved one. When I dug up the soil it smelt really bad.

If you wish to grow blueberries successfully, just plant them in good soil and then in the spring top dress with compost and aluminum sulphate to balance the acidity to the point required.

I was having problems after planting 6 high bush blueberries in an area cleared of wild growing low bush types. I mistakenly surmised that if the wild ones grew there, the high bush would do well. My brother who grows the high bush variety quite successfully to the point he gives away lots of 2 litre containers to anyone wanting them, advised me to do the above and this year all six bushes produced an abundant crop. I was surprised at the results since I thought three were 'goners'.

Around here, commercial blueberry growers prefer to plant in the glacial kettles, which are basically water-collecting depressions in the ground that filled with peat after the ice melted. So the blueberries are growing in peat soil, not pure peat moss, and in what was a wetland, but not with their roots submerged in summer.

Your problem may be having too much change in soil texture from the peat you added, to the native soil surrounding the hole. If you dug a hole in clay or sandy soil, and filled it with mostly pure peat moss, then you're going to have a drainage problem as the water does not want to move from the peat moss to the mineral soil if there's a sharp line between the two.

Some dire mis information being paraded. Or my readings are wrong.
Aluminum sulfate is toxic to the environment in general and to the fibrous roots of blueberries specifically.
Use Ammonium sulfate or something like hollytone.
Peat will lower the ph of soil unless its already extremely acidic
Mulch each year with pine needles that will maintain a low ph
Blueberries only require a hole 1' x 1' that's 1' deep. If you are having trouble with your mixture "bouncing back" you can afford to use pure peat amended with CURED pine chips.

Uhh, dude, the thread is six years old. You're too late. the barn done burnt down years ago, and covered over with a parking lot. Better luck next time, 'sides, pine needles don't do diddly, Bo. ;) M

This post was edited by Mackel-in-DFW on Wed, May 7, 14 at 8:38

According to everything I have read about peat moss pH over the years it is about 4.0. Tree leaves and pine needles have a pH in the 3.0 to 4.0 range and research done by Dr. Abigail Maynard at the New Haven Ag Research Station of UCONN found that tree leaves and pine needles did not significantly affect soil pH, so why would peat moss be any different?
Peat bogs are acidic but is that from the organic matter that is peat moss or something else, like being in an anaerobic state?
pH is a measure of the presence, or lack of, free Hydrogen ions and means "potential Hydrogen". Adding lime (Calcium Carbonate) to a soil with a low pH can raise the pH while adding sulfur to a soil can (by adding free
hydrogen ions) lower a soils pH. How many Hydrogen ions are in peat moss?

This post was edited by kimmsr on Thu, May 8, 14 at 7:42

Peat moss is full of hydrogen ions, because its complex carbohydrate-like structure contains organic acid functional groups. I think it is much more likely that the acidity derives from the peat itself rather than anaerobic conditions in the peat bog. All one has to do is immerse some peat in distilled water and check the pH. I will bet you a dollar the pH will be around 4.

As far as aluminum sulfate being 'toxic to the environment', this is the first I've heard of that. If it is harmful for blueberries, so be it (would be nice to have a reference on that though). The aluminum rapidly reacts with water and becomes aluminum hydroxides, releasing H+ which lowers the pH. Oxides and hydroxides of aluminum are very common in soils and rocks.

There is nothing "environmentally toxic" about aluminum sulfate. It is very commonly recommended as a means of more rapidly lowering soil pH than say something like agricultural sulfur.

"Rapidity and a long record of successful support for blueberries make aluminum sulfate the automatic choice for home gardeners who want to amend planting soil as they plant or do so only a few days before planting blueberry bushes. Quick-acting and convenient, aluminum sulfate can also be dug in annually around existing bushes to perpetuate acidic pH levels in the soil."

Aluminum sulfate is also very commonly used in hydrangea plantings to maintain or intensify the blue flowers. In fact, it is sometimes sold as 'hydrangea bluing'. There are some plants that DO have adverse affects to aluminum or with which aluminum toxicity can very easily build up - ericaceous plants for example - so it is best to avoid using aluminum sulfate around these types of plants and to always use according to package labeling.