advice on particular soil mix for blueberry containers?

15 years ago

I planned on experimenting with the following soil mix for blueberries (in container buried in ground).

1.40% peat moss (make sure this is raw peat moss, not treated in any way);

2.40% coir ("coir" is shredded coconut husk);

3.20% perlite; and,

4.a handful (per plant) of soil sulfur.

this mix is excerpted from a study posted at this link:

http://www.specialtycrops.colostate.edu/scp_exp_demo/blueberries.htm

I was wondering what the gardenwebprofessionals on the forum thought of this mix?

as for my amateur credentials: I have 30 blueberry bushes, 5-7 years old, many varieties, all in ground (not containers). So, I am an established and successful grower, just looking to experiment, but most importantly, love to take the advice from others on the forum.

thanks,

Bob

ps. I'm in Delaware, z7

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Comments (9)

justaguy2
15 years ago
last modified: 9 years ago
I think the mix will be fine for awhile (it's highly organic composition means it's gonna break down and need replacing quickly, probably after 1 season of growth). I read the info at the link and I am guessing you chose this mix because it maintained the best pH range over the testing period?

I don't know that I would build a mix with pH as the primary factor being considered since sulfur, vinegar and acid forming fertilizers can all be used. Still, to each their own.

I think as long as you keep an eye out for the structural collapse of the mix and repot before it becomes a problem you should do fine.

Clearly you have enough experience under your belt to spot problems right away. I envy the number of BB shrubs you have.
doggdoc
Original Author
15 years ago
last modified: 9 years ago
justa,

thank you for the reply. i have little to no experience with container/potted gardening, and that is why i had the question of the cocktail of coir/peat/perlite in a container.

on the other hand, my success with the BB is attributed largely, not solely, to my devotion to starting with a mix (different from above) that is aimed at pH more than anything else.

so, justa, i've read many of your responses to BB/soil pH, and i welcome the difference of opinion that you and i seem to share - i find soil pH paramount, you don't seem to, rather you attain it via watering and fertilizers. i'm glad to know your system works for you, and i'm going to try your idea of less soil pH attentiveness, more watering/feed adjustments for pH on some future bushes.

my concern was that the coir/peat/perlite mix may be too clumpy/muddy - i was hoping the perlite would break it up some. i thought of throwing in some humus and compost. thoughts on this?

justa - you're a valued poster, thanks again
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justaguy2
15 years ago
last modified: 9 years ago
my concern was that the coir/peat/perlite mix may be too clumpy/muddy - i was hoping the perlite would break it up some. i thought of throwing in some humus and compost. thoughts on this?

The trick is a mix that is always moist, but also supports good aeration. I think that the peat/coir/perlite will probably achieve that, but not for more than a season as they will begin decomposing and breaking into smaller sizes quickly. As this occurs the water retentiveness of the mix increases, but at the expense of air holding capacity of the mix.

Compost and humus would likely make the problem worse. I don't know what humus is in this sense as the stuff sold in bags isn't what I consider humus, it's often sawdust like stuff from what I have seen, but haven't looked in a few years. Compost will also break down very quickly.

What many growers use is pine bark as the basis of the mix. It also breaks down, but more slowly and it starts at an appropriate pH. Filix has reported good success with his blueberries in Al's 5:1:1 mix (5 parts pine bark fines, 1 part peat, 1 part perlite).

If you are concerned about the suitability of any mix you can test it in a clear cup. Fill the cup with mix, saturate it with water and then poke a hole in the cup so the water can drain. After no more water is draining, look to see if there is a water layer on the bottom. This would be the perched water table and blueberries aren't going to like it. If you just have an inch or less and you are using a reasonably tall container it's likely not going to be an issue, but if you have much more than that you are taking a risk with the shrubs. Keep in mind the organic component of any mix is going to break down over the season and the PWT will increase in height as it does. Some materials break down quickly, others more slowly. so, justa, i've read many of your responses to BB/soil pH, and i welcome the difference of opinion that you and i seem to share - i find soil pH paramount, you don't seem to, rather you attain it via watering and fertilizers.

It isn't that I consider pH unimportant, but rather it's next to impossible to control without continual monitoring. As you saw from the link you posted the pH of the mixes shifted throughout the test. With a quality fertilizer intended for hydro or container use many nutrients will be chelated and available to the plant even when the pH is out of normal bounds.

Unless one has testing equipment and is willing/able to respond appropriately to control pH swings (occur quickly and are short lived) and shifts (a longer term movement) it's not really worth fussing over, in my opinion.

Rather, by building a mix that starts out with an appropriate pH range, and neutralizing the alkalinity of the irrigation water via vinegar or using rainwater when practical there should never be a problem. Something to keep in mind is that the plants are getting nutrients from the water and whatever nutrients are dissolved in it, not (so much) from the growing media. If the pH of the water/solution around the roots is good, then the plant is happy too ;)

BTW, are you a veterinarian? Just wondering due to your handle/name/alias ;)
doggdoc
Original Author
15 years ago
last modified: 9 years ago
yes, i'm a vet, and my wife is too. my dog's love to eat the blueberries.

justa - thanks for the reply, again. very informative.

i've decided to search for some pine bark mulch, and do a few in al's mix, and a few in the other mix.

all i've seen at the HD/lowes is pine bark mulch in bags, and it is usually nuggets - i suspect this is not what you are talking about, right? or could i get away with shredded pine bark mulch in bags from a big store, or nursery? i'm searching today

bob
tapla (mid-Michigan, USDA z5b-6a)
15 years ago
last modified: 9 years ago
Just a note to you guys - Doc needn't be so critical of drainage issues because of the fact that his containers are partially buried. He should have no perched water issues in those containers - regardless of soil choice .... so long as it's reasonable. ;o)

Al
justaguy2
15 years ago
last modified: 9 years ago
ah, good point, Al, I missed that entirely. Bob, will the potting mix be in contact with the earth? If so then Al is right, drainage is going to be different. As long as the earth isn't flooded there won't be any PWT in the container regardless of the mix you use. You could use dirt/soil and be fine.
doggdoc
Original Author
15 years ago
last modified: 9 years ago
can someone elaborate on the pine mulch al's mix question i have?

all i've seen at the HD/lowes is pine bark mulch in bags, and it is usually nuggets - i suspect this is not what i want (not nuggets), right? or could i get away with shredded pine bark mulch in bags from a big store, or nursery?
justaguy2
15 years ago
last modified: 9 years ago
You can get away with it, but keep in mind that the larger the particle size, the less water the mix is going to hold. Some easily stumble upon an ideal product, others have to search a bit more and look to sources they normally wouldn't. If the typical particle size is larger than a dime it may retain water less than you would like with the shrubs.

Fafard makes a product called Aged Pine Bark Organic Soil Conditioner. Find a Fafard retailer and if they don't have it they may be able to order it. Do you have an Agway in your area? If so perhaps call them as I hear they carry Fafard products.
lsoh
14 years ago
last modified: 9 years ago
doggdoc,
Do you have any obervations to report regarding these two mixes?
Thanks

advice on particular soil mix for blueberry containers?

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advice on particular soil mix for blueberry containers?

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justaguy2

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