Remove 100% of the soil before repotting. If you don't you will have 2 different soils in the container with different drainage and water retaining properties.

Yes, you need the micro nutrients for best results. I am not sure what minors the MG will have, but based on other MG products I have seen it won't have calcium or magnesium. Normally this isn't a problem as we can just add lime to provide both, but blueberries HATE lime. A peat or bark based soil should be in a good pH range for them right off the bat.

So, you can supply calcium with gypsum and magnesium with epsom salts.

Perhaps a bit easier would be to mail order (unless you have a hydro store nearby) DynaGro Foliage Pro and be done with it (won't need the MG). A little more calcium in the form of gypsum isn't a bad idea, but you should be OK.

A 3 gallon pot seems a bit on the small side. They may have come in that size, but I would move them up to a 12" or so pot at least. They don't have the most extensive root system in the world, but they like to stay moist and cool.

Thanks justa. I orderd some 15 gallon plastic injection molded containers "squat". I already bought some dynagro foliage pro. That doesn't promote acid though. Should I use the dynagro every other feeding. Al said to use the miracid. He has been helping me along. And also you. I didn't want to bug him with more questions. Thankyou very much. filix

The miracid is fine, so is the foliage pro, it is just that the FP has all the nutrients making it simple to fertilize properly without worrying about additives to make up for deficiencies in the fert.

Miracid isn't really an acidifier as far as I know, rather it supplies nitrogen in acid forms. Most ferts have an acidfying effect anyway. If you are concerned about the pH of the solution it never hurts to add a tablespoon of household vinegar to a gallon of water.

As far as feeding frequency, it's your call. In an ideal world we would fertilize lightly with every watering, but in the real world this can become tedious. Blueberries aren't particularly efficient at nutrient/water uptake due to a lack of feeder roots. For this reason you want to have a mix that is kept moist, not wet (use a coarse mix and you don't have to worry about it) and you want a light to moderate amount of fertility at all times other than when the shrub is dormant.

Don't worry too much about pH with blueberries in containers it isn't as relevant in containers as it is in the ground. If you see any indications of nutrient problems, use a little vinegar to acidify the water.

I don't think acidity and fertilization are going to be big challenges for you. I think overwintering in containers will provide more of a challenge. They will almost certainly require some protection from the freeze/thaw cycle in zone 5, even if they are rated hardy to zone 3.

Let me start by saying that Im NO EXPERT...That being said,I understand what justaguy is saying about the two different soils but if they are in active growth and you disturb the roots too much you will cause a good bit of damage and shock to the plants.
I have just had these problems myself and I didnt even remove 100% of the soil,I just tried to loosen the root ball a little.
As far as Miracid goes,Im reading straight from the box,It has Boron,copper,iron,manganese,molybdenum and zinc.So that should cover the minors.
Im pretty sure the reason there is no Calcium is because acid loving plants dont like it???
Like I said there are many people here that know more than I do but just thought I would share what I have learned about my Blueberries so far :-)
Also keep in mind that if watering your Blueberris with tap water you will need to check the Ph and adjust it if needed.

Kev,

Calcium is absolutely required for all plants. There is no plant on earth that can grow for long with a complete absence of it. What blueberries do not like is lime which is what is commonly used to provide calcium and magnesium.

Filix,

As you start out with container blueberries I want to share a couple secrets to success with you. You may regarding me as having years and years of extensive experience killing countless numbers of these shrubs.

Like most, I thought failure must be due to lack of acidity, nutrients, drainage etc. These are important factors for long term health of the shrubs, but they are *not* the primary cause of failure with blueberries.

Over the years of one dead plant after another I compared my failures with the failures of many others who concluded blueberries just couldn't be grown in containers or in my area even in the ground.

I found a couple common denominators among the many failures. They aren't what you are likely to think they are.

They have nothing to do with drainage, acidity, nutrients or any of the things most would think critical to survival.

Here are the 2 most common causes of failure with blueberries:

1. Failure to purchase shrubs at least 3 years old. Yes, they are harder to find than the sticks in a box at the local big box store and they are often harder to find than the bare root or potted 1-2 year old shrubs at nurseries and garden centers, but if you start with a shrub less than 3 years old the odds are it will die before you get a single berry. You want a stocky plant that is well branched. Avoid plants with thin trunks and avoid plants with a lot of weak, twiggy growth. While even strong shrubs will produce some twiggy growth, a lot of it means a weak plant that will likely die. Get the oldest, stockiest shrubs you can find or the odds of failure go way up regardless of what you do.

2. Failure to take winter protection seriously enough. If you leave the container out during the winter in the same place the shrub grew during the summer, it will likely be dead come spring. An unheated shed/garage will do fine to keep the shrub alive during it's dormant period, but it will also result in the shrub breaking dormancy well before it can be safely left outside. You will have to deal with the ritual of out by day, in by night for weeks or longer.

Burying the container in a spot that gets no direct sun, waiting for the ground to freeze and then mulch is ideal. If the spot isn't protected from the dry winter winds, wrap it in row cover material, burlap or something similar to reduce winter kill of the branches.

That's it. Based on my years and years of experience killing blueberries those are the top 2 reasons for failure.

If you get the fertilization, acidity and even drainage wrong the odds are an older, healthy shrub will provide you with visible warning signs well before it dies. Buy a plant too young or expose it to too many freeze/thaw cycles and it will die with no or too little warning to correct the problem.

Well then I stand corrected about the calcium :-)
I had heard that some people choose not to use Vinegar to lower Ph due to the fact that after it breaks down it will leave calcium in the soil.
Like I said before...Not an expert by any means LOL

Does gypsum affect ph at all?
I may be needing to use it for my Blueberries as well ;-)

Gypsum has little to no affect on pH. It is a good source of calcium when you don't want pH going up.
I had heard that some people choose not to use Vinegar to lower Ph due to the fact that after it breaks down it will leave calcium in the soil.

It may surprise you to learn that some people use sulfuric acid to acidify irrigation water instead of vinegar. Either is fine, but ordinary household vinegar is much safer to handle ;-) When I was younger I thought sulfuric acid was really cool stuff that would 'eat' anything. So I bought a gallon and experimented with it for nefarious purposes. It was in a glass container and a friend who had just saved up enough pennies to buy a truck (his first vehicle) had it in the bed of his truck. It got tossed around and the glass broke. We both then learned how quickly it 'eats' paint ;-)

Vinegar is very effective at acidifying irrigation water and it doesn't break down into anything harmful. It is also available in shatter proof plastic containers ;-)

LOL LOL LOL
Nice story...I will definitely be getting some gypsum now.
Thanx for the info ;-)

Thanks justa and kev. Good info on how not to kill my blueberries. Your right, 3 year or better plants are harder to find. They are pricy too. But worth it. I have a large garage "unheated". But its only about 10 degrees warmer in there in the winter. I'm going to put two of the zone 3 ones in half wiskey barrels, just to see if they do better than in a 15 gallon plastic container. Those I was thinking of leaving out but covering them with hay or something. The plastic ones will be easier to move. I bought some miracid today. filix

Good luck and keep us posted :-)

Filix & I had chatted a little off forum about his BBs and their nutritional needs. I had shared a few comments with him that I thought might be of interest, so I'll share here, too:

BBs have some pretty unique nutritional requirements compared to most other plants. They grow in acidic soils where fertility is usually quite low. Also, the predominant form of available nitrogen (ammonium) is usually present at levels that could be toxic to many plants. However, BBs have mechanisms to cope with the acidic, ammonium-rich, nutrient-poor conditions. They form a symbiotic relationship with certain fungi, which derive carbohydrates from the inner portions of the BB root system, and in return, help extract nutrients (especially phosphorus and nitrogen) from the soil for the plant. So, in comparison with many other plants, BBs have very low nutritional requirements. In fact, they can be quite sensitive to high levels of some nutrients, and a heavy fertilizer application can injure them, so be sure you fertilize at reduced recommended strengths (1/4 - 1/2 strength, weekly to bi-weekly).

BBs also have the unique ability to directly absorb ammonium ions. Most plants absorb N in nitrate form, which is then converted to ammonium by a metabolic process before being incorporated into proteins. However, nitrate fertilizers can be harmful to BBs. For this reason, ammonium forms of fertilizer are recommended, such as ammonium sulfate or urea. Ammonium sulfate is particularly good because it acidifies the soil, and most soils tend to have a pH higher than 4.5. (Foliage-Pro 9-3-6 offers 2/3 of its N in nitrate form, which is normally a good thing, but not particularly desireable for BBs.)

Someone upthread made the comment that there is no Ca in fertilizers for acid-loving plants because they don't like it. JaG points out that ALL plants need Ca, which is true. The reason there is no Ca in most of the fertilizers we use on container plants is simply because of solubility issues.

The fact that different species of plants tend to grow on different types of soil does not mean that the one needs more of a certain nutrient than the other. It just means that the plants have developed strategies to adapt to certain conditions.

Acid-loving plants have adapted to acid soils. Their need for calcium is still the same as any other plant, and their nutrient requirements do not differ from plants that thrive in alkaline soils. The problem for acid-loving plants is that they have not developed a method to limit their calcium uptake, and will absorb too much of it when available, resulting in cellular pH-values that are too high. Some acid-loving plants also have difficulties absorbing iron, which is tightly bound in alkaline soils, another reason why they thrive in low pH soils. This all pertains to the plants ability to handle nutrients, not to the actual nutrient needs of the plant.

Filix is concerned about micronutrient availability if he uses the MG 30-10-10. It contains all the micronutrients that are likely to be deficient in container soils, but glaringly absent are the secondary macronutrients Ca and Mg ... S as well is missing. Supplying the Ca with gypsum and the Mg with Epsom salts is probably the best plan. Though insoluble, enough S can be had by including a tsp of elemental S per gallon of soil.

Al

Thats the most in-depth and detailed post on blueberry needs that Ive read so far :-)
Thanks for the knowledge,Im sure all of us amature blueberry growers out there will benefit from it.

Wow. Great thread!

JAG, can you elaborate on the idea that pH is not as important for blueberries in pots as in the ground? Al, do you concur?

I've just put in 9 blueberries in pots. I am concerned about my container pH - I used Al's gritty mix, so it's way above 4.5, and I'm not sure that watering with vinegar will bring it down. Doesn't the soil buffer the pH? (Right now, they're just mostly getting rain.)

I did use sulfur but I understand it takes a long time to affect pH. I've been watering with fungal compost tea because I understand that will tend to buffer the pH lower. I would prefer not to use any inorganic ferts (just cause I'm difficult that way.... I'm a soilfoodwebbie).

Jenn

Jenn, Al can explain the soil science much better than I can, but the pH issue relates to nutrient availability. In a mineral soil the availability of nutrients in that soil is determined by pH.

In a container we don't use soil (I hope) so the chemical reactions aren't as significant. We generally don't have our nutrients tied up in the growing mix itself, but in the water we irrigate with. If the water we irrigate with has the nutrients required for the plant, then the plant gets the nutrients.

In the soil, people have 'liberated' nutrients from soil by drenching with acidified water. The water, being acidic, dissolves the nutrients and surrounds the roots which then take them up along with the water.

I think a key thing to understand is that plants do not take nutrients from soil or potting mix, but from water. First the nutrients have to dissolve into the water. In the ground the soil generally holds the nutrients, but in a container our watering can is where the nutrients come from ;-)

I am not saying to use an alkaline growing medium, but I am saying to pay more attention to the pH of the irrigation water than the potting mix in a container as that water will have more of an affect than potting mix pH on the plant's ability to get the nutrients it needs.

Like I said, Al can explain it better than I can and if anything Al says differs from what I say, go with what Al says.

Anyway, I am not sure Al's gritty mix would be too high a pH as long as you didn't add lime. I think the bark is around 5.5 or so which is the upper end of OK, the peat would be around 4 or so which is great and if you used Turface or perlite they are chemically inert so their pH is irrelevant (tho I think it is around neutral).

Thanks Al for the summary. And thankyou justa for your good suggestions. I love this forum . I always get such reliable help.

I cant imagine growing bbs in That fast mix. I'm sure they would grow well but watering would be a chore. The tropicals I plan on bringing back in the house I'm growing in the fast mix. Two jasmine, two corkscrew vines and one sweet olive. justa wasn't kidding when he said 3 year or older bbs are kind of hard to find. I wish there was a nursery around here that had them. When I see some at a nursey and ask how old they are, most don't know.filix

Raintree nursery will do mail order for 3 year old shrubs (bareroot). Sometimes they advertise it on their website, other times you have to call and ask. I think they call them their "3x3" blueberries or something, but they have many varieties in this age/size available.

If anyone wants some, get them now as I don't think they ship them once they break dormancy, though they might keep them dormant awhile longer.

JAG, can you elaborate on the idea that pH is not as important for blueberries in pots as in the ground? Al, do you concur?

Yes - I do. Mineral soils in general hold nutrients much more tightly than the highly organic soils we grow in. If you'll consider: Even the gritty mix I often use is still highly organic at 2/3 inert ingredients: 1/3 (33%) bark as compared to the sandy soils the BBs are usually grown in with an extremely low organic component (usually Fertilizers affect media solution pH and make it easier/more difficult for certain types of plants to extract nutrients from soil solutions. Often, the plants themselves add ions to the solutions to actually change solution pH and make it easier for the plant to take up ions. The fertilizers we would want to use for blueberries will have an acidifying effect due to the ammonium nitrogen content. Fertilizers that form acids will be high in ammonium, ammonia, and urea. During nitrification, ammonium is converted to nitrate in the media, and in the process H is released which lowers pH. Plants also secrete H into the media whenever they absorb ammonium.

Fertilizers containing nitrate in the form of calcium/potassium/magnesium/sodium nitrate all tend to cause an alkaline reaction and raise container solution pH.

Although the most important factor in where media solution pH will fall is the alkalinity of the irrigation (which includes the fertilizers added) solution, it's not the only factor. We need to not only consider the fertilizer, but also the pH of the medium components, the liming materials used in the medium, and the pH/alkalinity of the irrigation water before adding fertilizers.

Finally, the gritty mix should be fine for BBs if you use gypsum as a Ca source. You'll need to water fairly frequently if you use it, though. Turface and granite are both mildly acidic, and the bark will be around pH 4.5-5.0.

Al

Hey filix I hope you dont mind me asking a question to Al and JAG,figured it could benefit us both to know the answer ;-)

The question is...Is rainwater with a pH of 6 too high to water our Blueberries?

Thats what mine is here in SC,just collected some and tested with litmus paper.
When I use tap water and add vinegar I get pH down to 5.

Like I said not trying to hi-jack your thread and I almost started a new thread to ask this question but since the importance of getting the pH of our irrigation water correct was being talked about here I figured it(hoped it)would be ok ;-)

Rain water is fine, but I am surprised it's pH is that high. In my state (Wisconsin) 4.5-5.0 is the norm.

Anyway, my answer is I really do not know.

The thing to consider is that irrigation water with a pH of 6 or even 8 isn't going to cause an overnight problem. What it is going to do is cause a nutrient problem, over time. If you know what to look for it is very easy to spot and correct and in this way you can let the plant tell you what it needs.

This is actually fairly easy to monitor for. Acid loving plants (any plant really), when pH is too high for them, will usually show signs of iron deficiency before anything else. This is easy to spot on the newest leaves. Look for the new leaves to grow in smaller than the older leaves and be a lighter green or even yellow while the veins of the leaf remain green. If you are using a fert with iron (Miracle Grow has it) it's quite unlikely the deficiency is lack of iron, but pH being too high.

Don't confuse iron deficiency with other nutrient deficiencies. Sulfur will look similar, but not have the green veins and nitrogen will show on the older leaves first, not the newest.

If you see signs of an iron deficiency, add some vinegar to the water and it will clear quickly.

In other words, don't worry about it too much, just watch the plants and they will tell you what they need. If you start with a healthy shrub it will be hardy enough to endure these temporary deficiencies while you get a feel for their needs.

Don't mind a bit kev. This year I made a rain barrel system. Trying to be more green. Its been up for 3 weeks. Last night it rained. Cant wait to see if it filled my two barrels. filix

Thanks Al and JaG - very helpful info. I'm not gonna stress on it so much.

I would add to JaG's advice on the 3 year old plants - you get what you pay for. All the ones I bought through mail order were 3 year or older, but some are tiny sticks and some are huge field-grown plants. NONE of them were pruned correctly (although the bareroot ones were supposed to be, yet every one of them has crossing branches!)

The last one I bought just Thursday at the first Farmer's Market of the season - from a local nursery. Wow, I wish I'd bought all mine from this source - a beautiful, 4 year old plant, ready to bear, and pruned correctly! I should have done more local research before mail-ordering.

The "sticks" cost about $10 each with the shipping.
The large field grown plants were $25 each with the shipping.
The 4 year old plant from the local nursery was $35, but beats the pants off all these other plants.

Jenn

I just planted my first two. Not easy to separate the roots from the dirt. I bought these from four different places. One of the two was filled with earth worms. I belive I got them all out. The second one was one solid block of roots. I wanted to save all the roots I could. So I used my garden hose on full to try to wash out the dirt from the roots. I didn't get all the dirt out. Glad there was no worms in this one. Can you rip some of those fine moss like roots out if you have to? Got eight more to do. Thanks. filix

I have a set of six blueberries. I got them last year from Starks. They sell a collection of 3 varieties, one for north and one for south. I got the south. I had them planted in our front yard with a very high peat mixture advised by a friend that grows u pick blueberries. We moved to an apartment this fall, so I dug them up, potted them up. Around here you can buy azalea soil and fertilizer mixes that folks have told me blueberries like.They're out on the balcony doing just great. They were all loaded with blooms and there are some big green berries on some. My blueberry friend said not to fertilize until they're at least 3 years old. He also advises picking off the blooms until then to make the plant stronger. So this is my first year to leave the blooms on. He says the trick is lots of peat in the planting hole and to NEVER let them dry out. As you can see, I'm in zone 7, so heat is the problem for us more so than cold. Honestly, I've done very little to them other than watering and they seem to be doing great. I think it's partly that they're from Starks. I have been very pleased with stuff from them although they are a little pricey. Also. I have them sitting where they are shaded from the hot afternoon shade.