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Best growing medium for sub-irrigated planters

Posted by gjshawk 6 (My Page) on
Mon, Jan 6, 14 at 21:48

Hi, everyone. It's been a while since I posted, because I don't grow stuff in the winter, but spring will be here in a few months and I am thinking ahead. Last year was my first with square foot beds, and I had quite a bit of success, but I also had three Grow Boxes that performed very well also.

My plan for this year is to continue with the four raised beds, the three Grow Boxes, and add some more containers using the rain gutter watering system. I'm going to automate the watering with float valves and such in the rain gutter system, and maybe even convert the Grow Boxes to float valves. I have a family reunion coming up in July and I know I will be gone for about a week. I don't want to come home to a dead garden because of lack of water.

I'm posting because, even though I'm told to use potting mix for sub-irrigated planters, last season I used Mel's mix and had good success. There might be something better out there that I don't know about but one of you might, so please let me know if you are an old hand with sub-irrigation.

Also, I had a problem with blossom end rot with my tomatoes in the planters. Not so much in the raised beds. Thanks in advance for the good advice.


Follow-Up Postings:

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RE: Best growing medium for sub-irrigated planters

Have you heard about Raybo's Earthtainer? The potting mix he recommends in his latest guide is 3 parts of a quality peat-based mix like Promix, 2 parts pine bark fines and 1 part perlite. This mix has better aeration and is less expensive than straight bagged mix. Vermiculite and compost can be a problem in a container. You can read about it and download his guide on the Tomatofest website. The "advanced" recipe is in the appendix.

Here is a link that might be useful: Earthtainers


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RE: Best growing medium for sub-irrigated planters

Thanks, Ohiofem. I'll check into your recommendation. I've read about the gritty mix and the other one, but my understanding is that they are for top down irrigation. I'm doing the bottom up kind this coming spring. Can't wait for all the snow to melt and the days to warm up so I can get started. I'll see if I can correct the mistakes of last year.


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RE: Best growing medium for sub-irrigated planters

Raybo's mix is not the same as gritty or 5-1-1 mix. It is specifically intended for "bottom up" watering. That's why the largest proportion is peat. (Promix is 85% peat). Like the Earthbox people, Raybo's does not recommend either vermiculite or compost, which make up one third each of Mel's mix. Both can become too soggy in a saturated mix.


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RE: Best growing medium for sub-irrigated planters

I should have mentioned that both the Earthbox formula and Raybo's add one cup of dolomitic lime per cubic foot of soil to add calcium and magnesium, which can help prevent BER. SIPs also need the lime to keep the mix from being too acidic for most veggies.


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RE: Best growing medium for sub-irrigated planters

Thanks again, Ohiofem, for the post. I'll give the Raybo's mix a try this year. Thanks also for the info on the lime. I've wondered how much to add per cubic foot. Last year I didn't add any and had a BER problem. I'll save my compost and vermiculite for the square foot beds and get some of the other ingredients for the sub-irrigated stuff. Can't wait to start. Still have snow though.


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