Best soil mix for blueberry raised bed?

Does anyone have insight into the pH tolerance of the following high bush varieties?



I use a 50/50 mix of peat moss and pine fines, mixing in a handful of soil acidifier and hollytone for every couple of gallons of mix. The plants seem to do really well in it, but there is definitely some compaction over time. I top dress with pine fines (after sprinkling on some more acidifier and hollytone) in the spring to keep the rain and watering from compacting the peat mix as much.


Does anyone use any perlite or vermiculite in their mix? I have some extra laying around and wondered if it would contribute to the structure, but was concerned it may result in too much drainage when the blueberries need to stay moist.

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Well they are different, perlite being better for drainage while vermiculite enhances water retention.

Is not like your soil would turn into a sieve if you use perlite.

Pine fines and sharp sand is all we use. That with a fertilizer for acid loving plants and you are good. Blueberry grow wild here (SW GA) under pine trees. You find them all over.

Having trouble sourcing pine ‘fines’ in my area. Lots of pine mulch but I don’t know if it’s what I’m looking for. Does anyone have a picture of how fine the ‘fines’ are? What’s the consistency?

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Fines are shredded pine bark into little bits.

Pine mulch is useful for lots of things, but not quite the same product.

I received several blueberry plants in 2 gallon pots that are extremely healthy and happy from a trade.

I pulled them out of the pots to see that they have obviously been growing in large chunks of pine …not fines but big thick chunky like pine mulch. but it doesnt look like all bark…it looks like woodchips of pine. Like the cheap bags of Pine Mulch.

I cant find a speck of anything in them other than this mulch and the roots are all embedded and thriving in them.

I am mixing local sand, peat and pine fines for my plantings but it makes me wonder if i should go much heavier on the chunky bark instead.

I think i am going to grow a few in 17gal pots and am wondering if i can go heavy on the chunky bark and light on the peat…

This is $4/bag locallly


I don’t know how “chunky” that one is but the growing medium in my half barrels is ~1/3" shredded pine bark mulch. The rest is peat, sand and topsoil.

It looks kind of like this…

as opposed to the “pine bark nuggets” which look like this:


My latest soil test if my blueberry planters doesn’t look good. My recipe: 3 parts pine bark nuggets 1/4 size. 2 parts peat. One part DE granules. These planters are 6’deep, drip irrigation. There are limestone caps which I need to do something about. My Ph is all out of whack.



Sort of like asking ‘is this detergent the best’.

Peat and bark are good…but ‘best’ has never been my criteria. Keeping the plant alive has been my goal…not perfection.

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DE has a high PH. That may be your problem.


@Newfroot — I added a bunch of peat to my blueberry beds… mulch with pine bark mulch… fertilize with hollytone which includes some Sulphur to help acidify.

None of that is too bothersome…

But I am also in the South and grow RabbitEyes… which don’t seem to mind my Ph hanging around 5.5. I have bushes over 7 ft tall and quite bushy that produce lots of berries.

I fertilize mine 2x a year… early spring around bud swell… and as soon as the last berries are harvested.



I also use DE in my mixes and pH is low. Even pine bark will increase pH as it composts. So adding sulfur yearly helps me keep pH in line. I like to use DE to add silicon and to help the soil retain water. It works but you only get a day or so extra between watering. DE has been studied extensively and the benefits are well documented. Disney uses it in all its gardens.
Having said that if you are having a hard time keeping pH low it might be best to lower amount of DE or eliminate entirely. I’m not so I’m using it with my blueberries as they are very sensitive to dry conditions. DE is my insurance policy. I use it with all my plants in containers. Soil is recycled in raised beds and after a decade are full of DE.


Those that think an increase in average temperatures is going to keep climbing…should definitely plant rabbiteye bushes…expecially in zone 6…since it’ll be zone 7 given just a little more time.

I find the southern highbush and the rabbiteye both tolerate 6 p.h. just fine. Even 6.5 sometimes.

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hmmmm… it seems your total Cation Exchange Capacity (CEC) is ~ 19 meq/100 with 3.4 of that being acid (aka proton). It is not clear how much of that is from the peat and how much is from the diatomaceous earth and how much is from the pine bark. I would not have expected the peat alone to have such a high non-acid component to the CEC. Although diatomaceous earth is mostly silica (silicon dioxide) which is fairly neutral in pH and does not exchange cations, it can also have things like calcium and magnesium. These can be exchanged for other cations and contribute to CEC and as they are alkaline they will raise the pH.

You might add some sulfur to lower the overall pH. Presuming that your soil sample is representative I might start with a little, ~ 1-2 grams of sulfur per kg of soil. (I added approximately that amount in my 3 half barrels that hold blueberries. There is no DE that artificial soil and the pH near the surface as measured by conductivity probe is generally in the 4-5 range.) The hope is that the sulfur will neutralize the alkaline components of the CEC. Presumably the organic acids from the slowly decaying peat will also eventually help to further reduce your pH.

Another option is simply to fertilize with ammonium sulfate during the year. In theory you would need a bit more than twice as much vs sulfur to achieve the same effect. Ammonium sulfate fertilization should also work faster but you would want to make sure you are not applying too much too fast.

The elemental sulfur is converted to sulfuric acid by soil bacteria. For this reason, it will likely take several months of somewhat warm weather for the pH to drop. This reference suggest this is on the order of 3 months, but I have seen other sources that suggest a year or more might be needed. In my limited experience one growing season does the trick. In any case you can always add a bit more sulfur next year if what you first added did not significantly affect the pH.
Effect on Chemical and Physical Properties of Soil Each Peat Moss, Elemental Sulfur, and Sulfur-Oxidizing Bacteria - PMC (2.4 g/kg is approximately the amount of sulfur that would be required to neutralize your alkaline CEC.)

@alan seems to have observed that the entire root zone of the blueberries need not be acidified for the plant to be able to obtain sufficient nutrition. If you work the sulfur into the top few inches of your pot you will hopefully soon create a layer near the top that is of lower pH. (I am sorry that my quick perusal of the site did not locate the actual post that I seem to remember. My apologies if I got that wrong.)

This last row of the little table assumes that 100% of the sulfur added can be oxidized to sulfate as sulfuric acid. I do not know this to be the case, however I have found some references that suggest this is possible.
What can be said is that this is the minimum amount of sulfur needed to neutralize all of the alkaline CEC in your soil as indicated by your test result.

I think I am out of words. I hope most of them were coherent and spelled correctly and that some of them were of use.



Yes, the literature generally seems to suggest that the pH needs to be adjusted throughout the root zone, but Carl Whitcomb did experiments with pin oaks that proved with at least that species only a very thin layer of pH acidified soil was needed for trees to draw adequate iron. With the knowledge of his research in mind I have since observed the same ability with blueberry plants on my own property and others, but the soil was more acidic about a foot down where my very vigorous and productive plants apparently draw most of their iron. Whitcomb’s experiment was with surface broadcasted sulfur.

Regular mulching tends to create a more neutral layer on top over time if sulfur is not used to compensate, but as long as the deeper soil remains acidic, plants will benefit from the mulch and not suffer the pH in the first few inches being up to about 6.5 pH. Blueberries tend to thrive in soil with high OM content.


Richard, thank you for your excellent explanation! I think I better get busy deciding what to mix in my soil.

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Alan, thank you for sharing your input. You all have been like big brothers to me!
I happen to have a big bag of this sitting around, it it an option?

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