container soil thing...

bullet08(7)September 27, 2010

hi all,

i read enough about soil thing on this forum to get myself completely confused.

i need to find out what would be a good soil mix for fig plants that i ordered. the thing is, i would just use miracle grow soil, but since it's going to grow something that my kids will eat (possibly) i want to make sure i'm using something that is good. i don't trust the soils around my house.. one of the reason why i want to use container.

i read and understand the use of turface/gran-i-grit/pine park mix. however, i know for sure, that thing will not hold water long enough during the day here. we have some rather big containers outside of my house with miracle grow soil, and plants usually wilt if we skip to water it even a day. at the same time, i like the idea of getting enough air to the roots.

what would be the ideal container soil mix around zone 7 where the day temp can go up to 100 degrees? i don't mind watering every day, but don't really want to water it twice a day.

pete

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tapla (mid-MI z5b-6a)

You can adjust the water retention of the gritty mix to the point it will hold considerable amounts of water, just by increasing the volume of Turface and decreasing the volume of grit, while keeping the bark fraction at less than 1/3 of the o/a volume.

The thing is, you can't start with a soil made with the primary ingredient(s) being fine - like peat/compost/coir, and amend it with perlite or other larger particles to improve either drainage or aeration, or change the ht of the perched water table. Perlite, et al similar, have virtually no affect on these properties; it simply reduces the o/a volume of water a soil will/can retain.

In order to reap the benefits from added aeration and improved drainage, you would need to start with large particles and build around those, instead of trying to build favorable properties into fine ingredients.

Al

    Bookmark   September 27, 2010 at 3:12PM
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bullet08(7)

Al,

A question regarding the ratio given.. what would be the possible issue if I use 1/3 pine bark fine and 2/3 turface?

What purpose dose the gran I grit serve other than to add weight?

What exactly is pine bark fine? What can I substitute that with? Does pine bark mulch or hard wood mulch work as well?

Pete

    Bookmark   September 27, 2010 at 5:09PM
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tapla (mid-MI z5b-6a)

Hardwood bark/mulch and sapwood/heartwood of hardwood or pine break down too quickly, so N immobilization is always a problem, along with premature structural collapse of the soil. The rapid decomposition of the hardwood also generates a considerable amount of heat (like a hot compost pile) and can be an issue in that regard as well. There is also usually a considerable upward spike in pH when hardwood bark/mulch.

This is what the bark products I use in the gritty mix look like:

The bark at 3, 6, and 9 would need to be screened over 1/8" screen to remove the fines. The white fir bark at the top is available in some places prescreened in a 1/8-1/4" size, which is ideal. The soil in the middle is the 5:1:1 mix when it's dry. There really is no substitute for conifer bark, other than a different species of conifer (fir, hemlock, redwood, pine bark are all suitable).

There really is no issue if using screened Turface:bark, 2:1, except maybe more water retention than you want/need. Turface and bark will hold a LOT of water. The purpose of the granite is to add adjustability (for water retention) to the soil. If you want to maximize longevity and aeration, soils that have a small organic component - less than 1/3 of the soil, are best. If you have a 2/3 (of the o/a volume) Turface component, your water retention is what it is - considerable, with no adjustment; but, include whatever fraction of granite you wish to fine tune, and you have a very wide range of adjustability.

Al

    Bookmark   September 27, 2010 at 6:05PM
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bullet08(7)

al,

thank you for the information. i will consider it.

pete

    Bookmark   September 27, 2010 at 8:17PM
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foolishpleasure

I just planted my fig trees in garden soil I bought from Home Depot. I mixed with it some Cow Manure. They are doing great. I water them every other day.

    Bookmark   September 29, 2010 at 3:50AM
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tapla (mid-MI z5b-6a)

Growing in containers is something like a journey. We don't start on the journey at the same time, travel at the same pace, and we don't pass the way points at regular intervals. My journey has taught me that a mixture of mineral soil and manure is going to be very problematic for a very high % of growers; so while you may feel that is a perfectly suitable mix for your purposes, it is unlikely many would hold the same sentiments after trying it.

Judging how 'great' a plant is doing is as subjective as judging a beauty contest. What looks good to me, may not look good to you at all. The reverse is also true. Soils like you describe have always been very difficult to use in containers, and can always be expected to offer a greatly reduced margin of error for the grower. The advice that mineral/garden/topsoil should be avoided for use in containers whenever possible is offered for good reason, so if you're able to grow trees in it, you should be congratulated. I'm sure I wouldn't be as fortunate, based on the results I'm used to, using soils with more aeration and that drain better.

Al

    Bookmark   September 29, 2010 at 10:52AM
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foolishpleasure

Thanks Al
My Figs in containers with the the mixtures of top soil an cow manure are happy and healthy. I judged that by the number of delicious Figs the whole family is enjoying. As for drainage I made sure the Pots are very well drained. My problem is not the soil mixtures but it is the roots crowded in the pots even I use large pots. My next plan is to drill holes in the sides of the pots and dig them in the garden to give the roots a way to expand. I got this idea from a Gentle man at the County extension.

    Bookmark   September 29, 2010 at 3:59PM
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tapla (mid-MI z5b-6a)

Ahh - from a hydrological perspective, partially burying your containers turns them into mini raised beds & allows you to use soils much finer than what many consider wise for more conventional container plantings. Nurserymen often employ a similar strategy & put the name 'pot-in-trench' on it

Good luck with your endeavors, FP.

Al

    Bookmark   September 29, 2010 at 5:44PM
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