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Acidifying Soil For Blueberries

powerofpi
8 years ago

I recently planted 4 "Sweetheart" blueberry bushes in a 10'x10' garden area. I began to read more about them and learned that blueberries need soil with plenty of organic matter and extremely acidic conditions in the range of pH of 4-5. I quickly bought a pH meter and discovered (to my horror) that my soil had a pH of 7.3! Also, it was rather sandy and without too much organic matter.

Ideally I would have learned all this and amended my soil *before* planting my blueberries... but hindsight is 20/20. In the past couple weeks, I have mixed 180 pounds of peat, 60 pounds of shredded tree bark, a considerable amount of finely-shredded corrugated cardboard, and 12 pounds worth of elemental sulphur into the soil. I removed the blueberries, mixed all of this into the top foot of soil, then put the blueberries back.

My pH has dropped from 7.3 to 6.8, which is still way too high for the blueberries to thrive. I understand that sulphur may take months or even years of bacteria breaking it down in order to significantly lower the pH. Should I take steps such as watering with diluted sulfuric acid? I want my pH to drop rapidly, but I also don't want to accidentally overdo it once the sulphur begins to kick in. I was thinking of watering with diluted vinegar in the mean time, which will have an immediate but temporary effect. Thoughts? Thanks in advance!

Comments (22)

  • Laurel Zito
    8 years ago
    last modified: 7 years ago

    Aluminum sulfate works fast, but I find it difficult to judge how much to use. Make some coffee water your plants with the coffee?

    This post was edited by tropical_thought on Fri, Jun 6, 14 at 0:08

  • cold_weather_is_evil
    8 years ago
    last modified: 7 years ago

    No real advice here, but please keep in mind the scale of the earth soil under our feet and how puny are our attempts to modify it's chemistry. The ground may have a lot more calcium in it that you may realize. You can't possibly have as big an effect on your soil at a garden scale as you would have on a bucket or tub scale, and what effect your additives do have will take years to take hold and stabilize. Think about containers.

    Having plants on hand forces one to look for quick remedies, but gardening is long term and you will need to go through the long term part. No real shortcuts. Geology is insisting that it has the say in your soil's pH, not you or I.

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  • plaidbird
    8 years ago
    last modified: 7 years ago

    Blueberries are very adaptable. Our soil in the neighborhood runs about 6.5 and everyone's blueberries do great. Most of us did add some peat in the beginning, but that was a few decades ago, so the soil has all wandered back to the 6.5 it wants to be.

    So the question needs to be how well do blueberries adapt to your 7.3 ? My guess is they will be fine. But check over in the fruit and orchard forum for posts on blueberries. I see those discussions over there often.

    Just for fun... what was the ph of the soil they were growing in when you got them ? A plant growing in one extreme, then dropped into the opposite extreme is going to struggle for awhile.

    Another whole topic is the fact that ph meters are notorious for false readings. At least the ones available for home owner purchase.

    Here is a link that might be useful: short cut to that fourm for you.

  • Kimmsr
    8 years ago
    last modified: 7 years ago

    Where in the United States are you?
    There are cultivars of Blueberries that can do well in soils with higher soil pH's and there are cultivars of Blueberries that grow better in New York than in Washington.
    Sulfur can be used to lower soil pH as well as Aluminum Sulfate.

    Here is a link that might be useful: growing Blueberrries

  • IanW Zone 5 Ont. Can.
    8 years ago
    last modified: 7 years ago

    I would recommend sulphur as kimmsr has suggested.
    Aluminum sulphate is a heavy metal and will be detrimental to your plants as the aluminum builds up in the soil.

    Here is a link that might be useful: Soil Ph

  • powerofpi
    Original Author
    8 years ago
    last modified: 7 years ago

    Thank you all for the responses!

    kimmsr, I'm in central Iowa in zone 5A. We get pretty hot summers and pretty harsh winters. Last winter was the coldest in decades, and killed quite a few perennials.

    tropical_thought, I was reluctant to use aluminum or iron sulfate because I read dire warnings about metal toxicity. Coffee might be another interesting temporary acidifier.

    cold_weather_is_evil, you are definitely right that soil has a natural pH based on its components, and that a huge quantity of soil is much harder to modify than a small pot. You're also right that I have no idea how much free calcium is in my soil. What I'm after here is a viable short-term fix that will not overdo my long-term fix with sulphur. I was reluctant to use containers due to the harshness of Iowa winters. Wouldn't an above-ground pot expose the root zone to temperatures which are too extreme?

    plaidbird, I wish I had measured the pH of the soil they came in prior to planting, but I didn't. I've read posts from others who agree with you that blueberries can do fine at higher pH. As I understand it, the acidity allows them to better absorb nutrients... but if the soil is extremely rich in nutrients, it's definitely plausible that absorption rates could be OK at higher pH. I'm definitely worried about the effects of yo-yoing my little plants between extremes. Even though my pH meter was cheap, its readings seem to be fairly accurate on some benchmark materials.

    Thank you all for your thoughts. It sounds like commercial growers use sulfuric acid to immediately water the soil down to a precise, desired pH, and skip the guesswork and delay of adding sulfur. If I were to do things over again, this is what I would do *before* planting. Sadly, by adding considerable sulphur to my soil, I may have removed that option for myself. If I were to water with sulfuric acid now, I'm afraid that in 6 months time the sulphur I added would begin to drop the pH lower than I want.

    So I'm in a bind- my current pH is probably still too high, but if I do too much, my future pH may drop too low. If plaidbird is right about blueberries sometimes doing fine at a higher pH, perhaps I would be best served by doing nothing for now and waiting for the bacteria to begin converting the sulphur?

  • toxcrusadr
    8 years ago
    last modified: 7 years ago

    ians, thanks for the link to that fact sheet. I would be interested in more references on aluminum toxicity to 'the roots of the plants' (as the fact sheet stated). I'm not arguing whether that's true or not, I'd just like to learn more about it. I use some Al sulfate on hydrangeas and I also have blueberries that are NOT thriving and was thinking of using it on them also.

    Aluminum is not actually a 'heavy' metal, it's an extremely light one, as far as chemistry goes, so that fact sheet is not strictly correct on that point. "Heavy" metal implies toxicity to humans, at least to me, and Al is not only much less toxic than heavy metals like Pb, Cd, Cr, Ni and Hg, it is also quite abundant in the earth's crust and in soils. Having said that I have no idea what the upper limit is for ppm Al in garden soil before it begins damaging plants. That's what I'd like to know.

  • Laurel Zito
    8 years ago
    last modified: 7 years ago

    I copied some advice hydrangeas in ohio:
    "1 1/2 tbsp. aluminum sulfate per gallon of water EVERYTIME I water my hydrangeas. Not once or twice a year but everyday (reduce to 1 tbsp. for potted plants)"

    I don't think it would be harmful unless you used a whole bunch of it. As can see people have been blueing hydrangeas for years and their soil did not end up all toxic.

    I also used it a lot before but only in small amounts, but now my soil is so good from composting for 20 plus years, I got some sulfur because it acts as a plant food. Just a tiny pinch, not like a whole cup of it.

    This post was edited by tropical_thought on Fri, Jun 6, 14 at 13:49

  • patricianat
    8 years ago
    last modified: 7 years ago

    I drove myself crazy trying to keep my soil at about 5 when I was growing blueberry bushes. I never could. I had blueberries. They did fine at about 6.5 - 7.5. I used a lot of coffee grounds. They are so good for the soil anyway. They keep the worms coming. I had the state offices, Starbuck, Cracker Barrel and Krystal saving them for me. I picked them up regularly. What a great garden had when I was doing that. Things changed, lives changed, times come and times go for the gardener who does large and the gardener who has to size down.

  • Laurel Zito
    8 years ago
    last modified: 7 years ago

    Can you post a picture of them? Are they ailing? It is much better to prepare the soil before planting, but there are other things that can go wrong besides soil problems. Peat Moss is high acid, but some times they add ph adjusters which ruin the whole benefit of using it.

  • powerofpi
    Original Author
    8 years ago
    last modified: 7 years ago

    tropical_thought, a picture is attached. You can see some leaves are turning reddish purple, which I assume isn't normal for the warm season. I don't know if this indicates transplant shock, unhappiness with pH, or something else.

    Anyway, the blueberry part of this conversation probably belongs in a different area of the forum.

    This post was edited by powerofpi on Fri, Jun 6, 14 at 16:18

  • plaidbird
    8 years ago
    last modified: 7 years ago

    It is much better to prepare the soil before planting,

    Oh my gosh ! I had forgotten the garden guru in one of our little plant stores that refused to sell me blueberry plants, many years ago, until I had prepared the site for at least one year ahead of time. Wut ? Like that's going to work for most folks. LOL

    Patricia,
    Thanks for having my back. I remember stressing over my little plants too. But over the years I too realized they had adapted and my love of making good soil, composting, and flinging mushroom compost around most years seems to have worked out fine.

    Powerofpi,

    Glad I'm not the first one you heard say they adapt. I'm sure there's a point where blueberries would struggle, but the ph numbers we are talking about doesn't seem to be that point.

    I've remembered a little more. At first I mixed in plenty of peat and fed with acid loving plants type foods. Once a year I added either sulfur or aluminum sulphate ( sorry, I really don't remember). Then as the years passed I did that less and less. Not really intentionally, but that's just how things worked out. So one might conclude that the plants had lot of time to adjust ???

    I think part of the reason I replied last night is so I would remember to go out and look more closely at my plants this morning. I had been watching the berries, not the leaves.

    Turns out the plants could be a better shade of green, if one got picky. I'm pretty sure this is because here we have had sources of mushroom compost disappear the last years, and my annual ritual stopped. The plants have gotten a little home made compost, but not really a lot, because it just wasn't a 'project'. So I'm going to poke through my amendment shelf and see what's there and give these guys a light snack for now. I noticed mushroom compost is back on the menu at one of my fav fuel companies, but too late in the season, so next year I'll get back in the groove.

    But boy oh boy.. tons of berries this year. I saw a little song sparrow sit on one of the branches this morning and check them out. ha ha ha... yeah, that's how it's going to be She got my first raspberry the other day. At least I knew it was time to be looking closer.

    You can watch the leaves and if the plant is not absorbing nutrients, due to lack ( in my case) or being too alkaline preventing uptake, you'll see a gradual fading to more of a yellow, rather than the green you see now.

    I'm wondering if winter hardiness will be the thing you need to be more concerned about, as your cultivar is a southern highbush, rather than the northern highbush I would have expected to be sold there.

    I wish I had measured the pH of the soil they came in prior to planting, but I didn't.

    This is when you bring out the blond wig, sunglasses and trench coat. PH meter hidden in pocket, return to the nursery and when no ones watching check blueberries pots from the same grower. :)

    BTW, blueberries produce more berries when they have another cultivar, that blooms at the same time within ( I think it's 100 feet). I'll add a link at the bottom of this post for you. While it doesn't have your cultivar, your plant tag undoubtedly states if yours is early, mid-season or late.

    Personally I would watch and wait. More plants are killed by kindness that benign neglect.

    Oh, and coffee grounds are great to attract worms, but do not acidify the soil. They run pretty close to neutral, the acid went into to the coffee.

    Thanks for the topic. I'm having fun following along, especially with our science guys posts. They're the reason I read this group off and on over the years. Sometimes it refreshes my memory and sometimes I learn something new. Good job guys. :)

    Here is a link that might be useful: Blueberry bloom times, PDF file

    This post was edited by plaidbird on Fri, Jun 6, 14 at 16:20

  • plaidbird
    8 years ago
    last modified: 7 years ago

    Some cultivars spring growth starts out with reddish tones to the leaves, then as the season progresses they go to green. Check out if yours is one of those.

  • powerofpi
    Original Author
    8 years ago
    last modified: 7 years ago

    > Personally I would watch and wait. More plants are killed by kindness that benign neglect.

    I'm sure that's true! I'm thinking my best move at the moment is neglect, unless I see yellowing as you say.

    Sweetheart is a recently-bred cultivar which is supposed to be a northern/southern hybrid. It produces once in the early season and once in the late season. It's also supposed to be self-pollinating. I'll have to see how many of these claims are true :)

  • plaidbird
    8 years ago
    last modified: 7 years ago

    Sounds good to me. All blueberries are self pollinating as far as I know. But they produce more berries when there's a different cultivar near by. More is better! That gives you time to check out the fruit forum and learn who's in the know over there.

    I started thinking this morning where I could fit in one more plant. I have an early and a mid-season. I bet if I added a late, they might bloom close enough.
    Of course the fact that I'm considering more shrubbery is a little nuts. :)

    BTW, Welcome to GW.

  • gardengal48 (PNW Z8/9)
    8 years ago
    last modified: 7 years ago

    I will second (or third - lost track) the concept that blueberries are rather adaptable/forgiving with regards to soil pH. Oregon and Washington are two of the largest growers of blueberries, both for agricultural production (i.e. the berries) and for retail sales (the plants). And while our soils are acidic, they are only moderately so. Blueberries grow beautifully here with virtually no soil amending.

    Red coloring on new growth is standard for many blueberry varieties (standard for the entire Vaccinium genus) but I would wonder about the amount of water the plant is getting. Blueberries like consistently moist soils and dry conditions can also led to reddening foliage.

  • Laurel Zito
    8 years ago
    last modified: 7 years ago

    I had a similar problem with discolored leaves on pansy plants and some other bushes also such as Ternstroemia japonica 'Burnished Gold' . I thought it could be PH, I posted about it a lot. I finally decided it was a fungal problem as using a fungicide regularly, keeps it from coming back. But if you want to eat the berries you should not spray it.

    It looks like the older leaves and not the younger leaves have turned, and that could be fungus. You could maybe trim off the discolored leaves, and hope for new growth. It does not look well, but I don't know blue berries. The water is san Francisco is very alkaline and they are not recommended. In fact, no one grows them here, we can grow black berries.

  • Laurel Zito
    8 years ago
    last modified: 7 years ago

    If you don't fix up your soil, its just buy and die. I used to have that happened a lot, each time you replant if you amend the soil eventually the plants will stop dying, provided your zone and climate and location of the plant is correct. Such as shade plants getting too much sun or sun plants getting too much shade or maybe too much strong wind. If you look around and see what others have successful growth in your area, you can see what plants will do well.

  • powerofpi
    Original Author
    8 years ago
    last modified: 7 years ago

    Thanks everyone! I think I'll try doing nothing for now and just waiting. No doubt I'll be back on GW once I find new and creative ways to lovingly kill my plants ;)

  • Kimmsr
    8 years ago
    last modified: 7 years ago

    Be sure to add your location to your profile page, the USDA plant Hardiness Zone is of much less importance and only tells us about which plants might survive a normal winter where you are.
    Iowa soils are normally alkaline due to the amount of rainfall you get, so getting the soil pH down will be a continuing challenge as will be keeping it there. Get the level of organic matter in that soil up which will help buffer that soil pH.

  • Laurel Zito
    8 years ago
    last modified: 7 years ago

    I thought a lot of rain washed away all the salts and bad things from the soil. But, if there is a lot of rain, that can lead to fungal things if the leaves stay wet, due to it raining often.
    I found this blog when I googled blue berry and fungal, it has a lot of tips and take you from start to finish in growing blue berries.

    Here is a link that might be useful: these photos have the same leaf discolarations

    This post was edited by tropical_thought on Sat, Jun 7, 14 at 10:45

  • Laurel Zito
    8 years ago
    last modified: 7 years ago

    In the follow up blog to the one I posted above, he put the blue berries into puts with a special soil mix and the resulting blue berries bush look much healthy and have lost the discolorations, so it must be related to the soil after all and not to a fungal problem. He seems very willing to help, you can even email him, he posted his email if you have more questions.

    Here is a link that might be useful: blue berries without the discoloration

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