How large of a container do I need for a blueberry?

joewormSeptember 23, 2011

Also how deep should it be?


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fruitnut Z7 4500ft SW TX

I'm doing well with 5-15 gallon. One 15 gallon produced 18 lbs last year another 15 lbs. This is the Star plant that produced 18 lbs after harvest and moderate pruning.

    Bookmark   September 24, 2011 at 12:16AM
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tapla (mid-MI z5b-6a)

.... a copy/paste job from a previous posting, which is why it might possibly seem off topic at times:

How large a container "can" or "should" be, depends on the relationship between the mass of the plant material you are working with and your choice of soil. We often concern ourselves with "over-potting" (using a container that is too large), but "over-potting" is a term that arises from a lack of a basic understanding about the relationship we will look at, which logically determines appropriate container size.

It's often parroted that you should only move up one container size when "potting-up". The reasoning is, that when potting up to a container more than one size larger, the soil will remain wet too long and cause root rot issues, but it is the size/mass of the plant material you are working with, and the physical properties of the soil you choose that determines both the upper & lower limits of appropriate container size - not a formulaic upward progression of container sizes. In many cases, after root pruning a plant, it may even be appropriate to step down a container size or two, but as you will see, that also depends on the physical properties of the soil you choose.

Plants grown in "slow" (slow-draining/water-retentive) soils need to be grown in containers with smaller soil volumes so that the plant can use water quickly, allowing air to return to the soil before root issues beyond impaired root function/metabolism become a limiting factor. We know that the anaerobic (airless) conditions that accompany soggy soils quickly kill fine roots and impair root function/metabolism. We also know smaller soil volumes and the root constriction that accompany them cause plants to both extend branches and gain o/a mass much more slowly - a bane if rapid growth is the goal - a boon if growth restriction and a compact plant are what you have your sights set on.

Conversely, rampant growth can be had by growing in very large containers and in very fast soils where frequent watering and fertilizing is required - so it's not that plants rebel at being potted into very large containers per se, but rather, they rebel at being potted into very large containers with a soil that is too slow and water-retentive. This is a key point.

We know that there is an inverse relationship between soil particle size and the height of the perched water table (PWT) in containers. As particle size increases, the height of the PWT decreases, until at about a particle size of just under 1/8 inch, soils will no longer hold perched water. If there is no perched water, the soil is ALWAYS well aerated, even when the soil is at container capacity (fully saturated).

So, if you aim for a soil (like the gritty mix) composed primarily of particles larger than 1/16", there is no upper limit to container size, other than what you can practically manage. The lower size limit will be determined by the soil volume's ability to allow room for roots to "run" and to furnish water enough to sustain the plant between irrigations. Bearing heavily on this ability is the ratio of fine roots to coarse roots. It takes a minimum amount of fine rootage to support the canopy under high water demand. If the container is full of large roots, there may not be room for a sufficient volume of the fine roots that do all the water/nutrient delivery work and the coarse roots, too. You can grow a very large plant in a very small container if the roots have been well managed and the lion's share of the rootage is fine. You can also grow very small plants, even seedlings, in very large containers if the soil is fast (free-draining and well-aerated) enough that the soil holds no, or very little perched water.

I have just offered clear illustration that the oft repeated advice to "only pot up one size at a time", only applies when using heavy, water-retentive soils. Those using well-aerated soils are not bound by the same restrictions.


    Bookmark   September 24, 2011 at 12:36PM
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Fruitnut,that's a lot of blueberries from one plant!!

What is the soil mix you are using for the star plant in the picture? How large is that pot it is in?

How can I find out how to properly prune the plant for maximun production?

How many years will it take for the plant to produce that many pounds of fruit?

What type of fertilizer and how often do you fertilize?

Al, thanks for the indepth explanation.

    Bookmark   September 26, 2011 at 7:00AM
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fruitnut Z7 4500ft SW TX


That Star was planted in 2004 in a 15 gallon pot. I can't remember the mix but the plant just keeps getting bigger and has never been repotted. I now use a mix similar to 5-1-1.

Pruning is just a matter of removing the oldest wood, overly thick and crossing shoots, and thinning fruiting wood if needed. I've pruned a little more since that picture was taken and am shooting for 12-15 lbs next spring.

Properly grown it would take at least 4 yrs to reach 15 lbs on a productive variety.

If you want the finest blueberry money can buy get a Sweetcrisp. The name says it all, very sweet and so firm it's almost crunchy. All the reviews I seen rave about this very new variety out of Florida.

I fertilize once a week with one tablespoon 21-0-0, ammonium sulfate, in 4-5 gallons water. This is when I'm pushing for rapid growth on a young plant. An older plant like the Star only gets fertilizer 4-5 times a year or once with a slow release complete fertilizer.

This is a Sweetcrisp one year after using the above once a week fertilizer the prior summer.

This is Sweetcrisp exactly one year earlier.

    Bookmark   September 26, 2011 at 2:06PM
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Fruitnut: I have blueberries in the ground and only use 21-0-0 for fertilizer, but wonder about it's exclusive use in pots? 5-1-1 mix has little or no nutrient. Do you not need to add any other nutrients then 21-0-0 in pots?

Also, I assume you also do not put dolomitic lime with the 5-1-1 to keep it low pH. So there is not even much cal-mag to start the plants in. Do you start the soil with some basic nutrition before going to 21-0-0?

    Bookmark   September 26, 2011 at 3:20PM
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fruitnut Z7 4500ft SW TX


My mix is actually about 50:50 spaghnum peat moss and partially composted rat litter. The rat litter is wood shavings and rat droppings. I've never had any nutrition problems and the plants grow rapidly.

Absolutely no lime in any blueberry mix. That would be the kiss of death.

I do use Osmocote slow release complete fertilizer for acid loving plants from time to time. Last year I compared the Osmocote to 21-0-0. Plants grew about 20% more with 21-0-0. But both grew about 4-5ft in 6 months.

    Bookmark   September 27, 2011 at 6:11PM
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Fruitnut: Now you did it!

I just ordered TWO, count them, two Sweet crisp blueberry

Now beginning to end, if there is anything you can add other than what you already have, please do. I will be receiving small 1 gallon ones..I hope to get them looking like yours.:-)


    Bookmark   September 27, 2011 at 9:02PM
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I just realized something. Up above you said you use something similar to teh 5.1.1 mix. What you just described is no where close. I am a little confused. Sorry:( Please explain so I don't mess up..Thanks:-)


    Bookmark   September 27, 2011 at 9:05PM
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jbclem(z9b Topanga, Ca)

Fruitnut, where did you get these Sweetcrisp blueberries? I googled and could only find the FloridaHill nursery selling them, tissue culture versions. And does anyone know if they are sold in California?

Also, thanks for the ammonium sulfate usage information. I asked the question in April, but the answers I received either tried to talk me out of using it or went on about something else. It's nice to see someone actually using it without a problem.


    Bookmark   September 28, 2011 at 6:11AM
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I container grew my blueberries for a year before putting them out in the yard in 20" pots. Blueberries can get *BIG*. As in tree sized. My aunt has some "bushes" that require ladders to harvest.

I would say go with the absolute largest container you have room for and/or can find.

    Bookmark   September 28, 2011 at 11:13AM
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fruitnut Z7 4500ft SW TX


Don't know what else to say about my mix. I use it because it works and half is free.


I got my last 10 Sweetcrisp from Florida Hill Nursery. Nine are growing like weeds and one just sat there until thrown away. I've also gotten plants from True Blue and Miller plant nursery both in Florida. The latter two should have plants this fall but demand is high and the nurseries are still behind on orders.

Ammonium sulfate is a great fertilizer for potted blueberry. By dissolving before application I've overcome any issues of root burn.


Your back must be much stronger than mine. I'm getting about one lb fruit per gallon of media on productive varieties. Don't expect that much on Sweetcrisp but the fruit quality more than compensates.

Nothing in a container gets as big as inground. I'm getting fruit off all kinds of trees in 5-15 gallon pots. Most of those trees produce 3-5 years before needing repotting or up potting. This nectarine produced 36 fruit off THREE trees on STANDARD rootstock in a 15 gallon pot. Fruit brix was 22-35, very sweet!!

There are three trees in there. Pot is 15 gallon.

    Bookmark   September 28, 2011 at 12:47PM
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Hey Fruitnut!

"I now use a mix similar to 5-1-1".

"My mix is actually about 50:50 spaghnum peat moss and partially composted rat litter".

These two postings confused me and I just wanted to know exactly what you meant. They are both two totally different mixes and I was curious as to what you really used.

As for the size of the pots..
How in the world do you lift those things? If you up pot, then we are talking more weight! I was wondering if you also root prune to encourage smaller size containers and plants?

I think your plants look fantastic, and like I said, if there are any other secrets of the trade, please share. I am going to give it a wirl and see how I do. I will probably use the 5.1.1 mix without lime.

You must have no issues with overwintering since you get such a bushell! I have heard they need so many hours of cold time.

I just ordered two from that same place. I hope they do well. I will post them when I get them.;-0)



    Bookmark   September 28, 2011 at 3:56PM
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fruitnut Z7 4500ft SW TX


My mix is about as light as possible. A 5 gallon is easy to handle, 15 gets fairly heavy. I'll never again use anything bigger as some recommend.

Blueberry are more prone to issues than anything else I grow. Primary concern is pH. Rainwater, 21-0-0, and sulfur are your friends if properly used.

Good thing about blueberry is the plants are cheap if you get small ones. Don't give up if a few die. I've killed more bb than everything else combined.

Chilling needs of Sweetcrisp are very low. In zone 5 you couldn't keep them from getting enough chilling unless they wintered in your citrus environment. Two weeks in a 35-45F garage will do the trick.

In zone 5 they will probably need winter protection but you are good at growing and protecting other plants. You are also good at making things grow. Sweetcrisp is worth the effort.

    Bookmark   September 29, 2011 at 12:07PM
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Thanks a bunch. That helps a lot. It looks like they will have to be treated like my fig trees. I stick them in a very cold shed in which the roots will not freeze but temps can range all the way down into the low 30's for 3
I am assuming they are not cold hardy like my other awful tasting blueberry bushes which can take temps down into the teens and sometimes below 0 for days on end.

Sounds like you are familiar with these buggers after a few tries and I really appreciate it.

I hope I can get them to gorw as well as yours. I remember seeing bags of bluberries that I couldn't


    Bookmark   September 29, 2011 at 3:56PM
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I used to grow mine in containers. I used the 5.1.1 mix. Most of my pots were 15 gallon plastic injection molded with handles. I bought the pots from griffin greenhouse supply. Now that I have much more land, I put them all in raised beds. They are very happy. I highly recomend a plant dolly for all your containers. I still grow lots of stuff in containers. I made the soil for all my raised beds, so I didn't even have to mess with my soil. I have 15 bushes in 4 large raised beds made with 2x12s. I have northland,northblue,blueray,bluecrop,patriot,chandler,reka,elliott,earliblue,berkley,duke,jersey. This year was my first good size crop. All of these were highly recomended. Some are sweeter than others. Mike said his tasted awful."Hi Mike" All of these get full sun, that blueberries need. Northland,berkley,duke,bluecrop are very sweet. patriot are tart, Chandler "the largest berry of all" are not that sweet. Elliott are tart but they produce so late they are worth it. I am still getting fruit off the elliott. The tart ones you can use for pies. I would like to add more. Duke would be my first choise. I just thought I would add my experience. Good luck Joe. Filix.

    Bookmark   September 30, 2011 at 7:17AM
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dancinglemons(7B VA)

This place is really dangerous! I've already got two blueberries doing quite well in 15 gallon tubs. Now I've got to get 2 sweet crisp! Gotta stay away from this forum......... First must go to get 2 15 gallon pots for the plants which will arrive in the spring........

I need more space.......
Wonder what DH would say if I cut down the boxwoods in our back yard.........


    Bookmark   October 4, 2011 at 3:18AM
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Thanks for all the information folks.

Should I buy different varieties or will all the same variety work for pollination?

I think up to six plants will be all I want to plant.


    Bookmark   October 6, 2011 at 12:49PM
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fruitnut Z7 4500ft SW TX


All I can tell you about pollination is that my southern highbush seem to set every berry whether there are pollinator insects or not. This is in my greenhouse with or without bumblebees. So that tells me they are self fertile.

I'd only plant Sweetcrisp from now on except for one fact, if I do I'll only have fruit for about one month, maybe two months. So I'm keeping Star as an earlier fruit and need to find something else for later.

You might as well get several varieties just to spread out harvest.

I have heard that Sweetcrisp holds very well on the bush but has low detachment force. I'm going to try to see how long they will hold on the bush. In the past I've had some very good fruit off Southmoon that was held on the bush about 6 weeks. I'm also going to try to force some plants early and delay fruiting on others. I'll do this by holding them in microclimates that vary in temperature and time of chilling. This is another reason for 5 gal pots, they can be moved around easily.

    Bookmark   October 6, 2011 at 6:18PM
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Well, lucky me!

It just so happens that my blueberry plants arrive with mealy bugs attached to them.

Been treating them ever since. Hoping them suckers don't come back next fall. It is the only mealies I have seen ever on my plants. It is a good thing that not all of us are ignorant to hijacked plants with bugs along for the ride.

Wish me luck with these plants. Thanks too 'Felix' for what you had to offer too.
Sounds like either you have made a whole lot of birds happy, or beat them to the bunch. Nice choice of plants!


    Bookmark   October 7, 2011 at 2:54PM
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Mike who did you buy them from with mealy bugs? I have been reading fruitnuts posts about sweet crisp and Im tempted. I dont want to order from same place. Fruitnut I would kill for your greenhouse! Filix.

    Bookmark   October 16, 2011 at 6:34AM
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Hey Felix!

I ordered them from the same nursery in Florida that Fruitnut got his.
The first thing I always do is overlook any plant that comes from somewhere else and noticed a few mealy where the branches meet the main trunk.
I wiped them off and then treated systemically since I won't be eating fruit from them until way after the treatment period.

I also kept them seperated from all my other plants just incase.

I don't know what to do with them? I must plant them for sure, but I wonder if I should bring them in after a frost, bury them deep into the earth until winter is over, or bring them into a very cold room that does not drop below freezing all winter?

What would you do? I couldn't find much info on them about overwintering or how much cold they can take.
I suppose since they come out of Florida, they would not be able to take our harsh winters? I wanted to plant them in-ground.


    Bookmark   October 16, 2011 at 7:06AM
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Thats Not very profesional. I tried to find out info. All I got was zone 53 I think? What ever that means. I would MUCH rather put them in a raised bed. I know someone in newyork who grows a fig outside. I have never seen his setup. But he uses a piece of plywood with insulation on it to cover for the winter. If they are as sweet tasting to me as they are to fruitnut, maybe it would be worth it to bring them in and out of a garage. Filix.

    Bookmark   October 16, 2011 at 12:08PM
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