Potting mix for blueberries?

castorpOctober 6, 2005

Does anyone have a good potting mix recipe for blueberries? I was reading somewhere that someone grew them in straight "Pine bark fines" (I guess that's finely ground pine bark) but I don't know where to buy pine bark fines and I was wondering how water retentive it would be. I imagine a peaty mix would work well, but I thought I'd check here to see if anyone knew of an exact recipe.

Thank you.

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tapla (mid-MI z5b-6a)

Blueberries like an acid soil. Planted in the ground, they are like potatoes: they love water, but insist on good drainage. I think a composted (or partially composted) pine bark soil with about 10% peat and enough perlite to insure good drainage would be an ideal choice. The pH of the mix I mentioned will be slightly acidic anyway. You can keep things that way by using an acid forming fertilizer like Miracid (I think they call it something else now) as required. If your water is high in pH, you may wish to use it (Miracid) exclusively. Resist the urge to follow suggestions to grow in a mix rich in peat to keep pH low. It will be more effective to use the pine bark, a little peat, & the fertilizer mentioned above.


    Bookmark   October 6, 2005 at 6:35PM
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username_5(banned for no reason)

My wife's grandfather grows blueberries in the ground. His soil is ph 7.0. He has grown blueberries for 25 years and still has some of his original stock doing well. He is a retired agriculture professor from the University of Wisconsin-Madison.

I recently developed an interest in growing blueberries in containers and I ran my ideas by him. I will share with you both what he has done for the last 25 years for in ground blueberries where the ph is too high as well as what I am doing in containers that I ran by him.

First, his method is incredibly simple. He digs a hole a foot deep (blueberries are all shallow rooted) and a couple feet wide and filled it with peat. Peat is around a ph of 4 when you buy it in the bags of just peat. Peat in potting soil mixes is ph adjusted to 6.5-7.0 by adding dolomitic lime. Blueberries hate lime and using anything with lime is a fast way to put them into decline.

He planted directly into the peat mixed with native soil. I don't know what ratio of soil to peat he used other than it appears to be mostly peat. Annually he top dresses with sulphur to counteract the surrounding native soils tendency to raise the ph. That is all he does. I made my choice to grow blueberries in containers because nobody around here grows blueberries in our soil. After finding out my wife's grandfather has been doing it for 25 years and seeing how simple and sucessful his method is I am thinking of putting some in the gorund as well as it would require less work than my container method.

My method for containers is to make a simple mix. I will never subscribe to mix 'recipes' that insist upon using hard to find or expensive ingredients as it is always unnecessary.

I use 70% peat, 15% compost and 15% pine needles or small sized pine chips. I use this because the pines are always available for free from the city as they mulch xmas trees. you don't need to use pine though and contrary to popular belief it does nothing to acidify soil. Pine is low ph, but it doesn't 'leech' the acidity into the soil at all. Peat does though. I just use it to add texture to the soil and because it doesn't leech anything alkaline into the mix. Compost is almost always near neutral in ph and this results in a mix that over time trends upward from 4.0 (the peat) to closer to neutral (the compost). Both compost and peat are well buffered meaning they resist ph changes. They resist ph changes by using the buffering capacity to neutralize anything that would alter the ph. Eventually this buffering capacity gets used up and the mix's ph can then change fairly rapidly in response to anything introduced to it. Most commonly what is introduced is water and fertilizer.

For this reason it is important to use low ph water and fertilizer in a container. In the ground the addition of sulphur can compensate, but this is trickier in a pot although I am sure it could be done.

What I use is rainwater because rain is naturally low ph. We have all heard of 'acid rain' right? Also using miracid or any fertilizer labelled for acid loving plants is the right choice. If storing rainwater isn't a viable option for your potted blueberries then an alternative which works well is to get a ph test kit from a fish store and test the ph of whatever water source you will be using. Fill up a gallon milk jug with this water and start adding white vinegar one teaspoon at a time and retest ph. When you get the water into the 5.0-5.5 range record the amount of vinegar per gallon it took and then simply add that amount of vinegar to each gallon of water before watering the blueberries. A word of caution on this though. If you use a municipal water supply the ph of the water might vary. Call the water utility and ask them for ph info. You may have to adjust frequently. If you use well water the ph should remain reasonably consistent although testing once a year or so would still be good. Also, if you use fertilizer in the irrigation water like miracid, test the ph of the water with miracid mixed WITHOUT adding vinegar.

1 Like    Bookmark   October 7, 2005 at 10:33AM
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Anita RM(Zone 8, Germany)

I realize this is a very very late reply to the above post, but thought I'd give it a shot anyway.

@ "username_5" - thank you for such a detailed description and for all the useful instructions!! I was just wondering....did you use regular peat or was it peat/sphagnum moss?

Thanks! Anita :)

    Bookmark   April 20, 2010 at 5:09AM
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