watering advise needed...please help

terratoma(7a)May 22, 2013

I'm having real difficulty in determining the proper amount of water to use on my plants; this is my first venture with containers. I'm sure that some would say just use your common sense but so much of that is developed from past experiences, don't you think? And those experiences were with packaged potting soil which got sloppy wet if you weren't careful. With Al's gritty mix and it's emphasis on aeration and drainage, I know the plants are going to thrive if they're properly fed and watered. For me the watering is a whole new ball game.
My gritty mix is equal amounts of fir bark, Turface and grit, all screened to be 1/8" - 1/4". I rinsed the mix and soaked it thoroughly overnight. In the days since planting, I've waited until the skewer came up with practically no dampness before watering again. I really doused the plants until water was pouring from the drainage ports. Easy, huh?
But while rereading (which I find myself doing a lot) many of Al's posts on water retention, trees in containers, etc., as well as the resulting threads, I read about a good method to use for watering. It goes something like this: Water slowly until water begins to seep from the holes. Wait 15 or so minutes. Then resume slow watering until the draining water is at least 15-20% of the total applied. (If I've read this wrong, please correct me...please!) So I gave it a shot. I tried it on 7, 5 and 3 gallon containers. I followed the steps as listed above, and came out with the same results in every case. After the first watering, one-third of the water drained away. After 15 minutes, I resumed watering very slowly; a higher percentage drained away! In one instance, 3 oz. out of a half-cup (4 oz.) drained. Other times it was 2 oz. out of 4 oz., 6 oz. out of 8 oz. (also, 5 oz. out of 8 oz.). I apologize for being so long winded. The point I'm concerned about is that, right from the beginning, much, much more than 15-20% of the water drained away ... and the percentages only increased as I watered more. Can I be watering too much? In this experiment, when I watered the tree in the 7 gallon container, I initially poured in three cups of water; one third drained away! Was three cups too much?
Please tell me if I'm misreading or misinterpreting the 15-20% advice. Better yet, will someone give me an estimate of how much water should be used for 7, 5 and 3 gallon pots? I know it must sound as if I want my hand to be held and, maybe to a degree, I am. ;-) I'm just asking for your advice where I went wrong so I can correct it.
Many thanks.

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A couple of thoughts:
1) Last time I checked on Al's current practices, he doesn't even screen Turface to that size (some folks do, but it's not strictly necessary). What I do is use a strainer to get just the finest particles out. I initially did screen to 1/8 in, but a) you get very little of it to use and b) things dry out pretty quickly (I could see that being useful for rot-prone succulent in plastic pots, but I doubt it's that much help compared to just watering less frequently).

2) If the mix is retaining moisture as you would want/hope/expect, I wouldn't worry about what percentage of water is draining out. When I water, I don't even go back after 10-15 minutes usually, I just water once with around a half-strength fert solution. This hasn't caused any problems, so far. In cases where I do go back for a second watering, pretty much water will start coming out immediately and most of what goes in will come out.

I believe the main reason for going back though is to allow for better fertilizer+moisture retention, as you've already thoroughly wetted the mix and overcome any hydrophobic resistance to moisture. And you're not just dumping fertigation water with fertilizer you spent money on. If you have no trouble wetting the mix well and aren't worried about wasting small amounts of fertilizer, I wouldn't bother.

Nothing in your post sounded like a real problem, per se (correct me if I missed something), so I think you may just be finding 'problems' to worry about for no reason. As problems go, that's way better than, say, spider mites or a root-rotted Home Depot plant that you didn't repot for a year. :)

    Bookmark   May 24, 2013 at 1:46AM
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I appreciate your explanations and advice. Yeah, I suppose I am a worrier, especially the first time around. Just trying to 'get it right' and am discovering there's more than one way to do so. ;-)
I remember Al commenting on screening the Turface with only insect screen; otherwise, too much was lost. (I found that out the hard way.) In this first trial run,I was just trying to follow some very early comments recommending keeping all three components about the same size (1/8"-1/4"). After reading about the many different adjustments growers have made in their mix, I'm sure I'll be doing the same. But I wanted to use the basic mix first to actually see/experience the improved drainage.
BTW, along with all that excess Turface, I have loads and loads of ReptiBark left over: it was larger than 1/4 so I didn't use it. Can I except a decent mix if I use this smaller Turface and larger bark in my next mix? (I assume the smaller size Turface would increase water retention a bit; would this be offset by the larger size fir bark?)

    Bookmark   May 24, 2013 at 4:36PM
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oops! I just discovered that you had already responded to my question (see above) about using the larger bark on another thread of mine. I hadn't checked it since Thursday. My apologies.
I experimented with some pine bark(as opposed to ReptiBark) yesterday. Sifted out the small stuff ( 1/4"). There was a pitiful amount that fell into the desired range. Sooo ... I put the large left over pieces through a food processor (which I confiscated from the stuff that was ready to go to Goodwill): two quarts produced a very small handful of usable bark!! Man, I hate to spring for more Reptibark. Only 30% of what I buy at the local PetSmart is a usable size (and I have six more trees for six gallon containers. What ... me "worried"? Nah. :) :)

    Bookmark   May 25, 2013 at 10:48AM
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