Can perlite be eliminated altogether?

edweather(Zone 5a/b Central NY)April 17, 2011

Hi. I have about 3/4 of a yard of double ground pine bark. It looks like it has a lot of very fine stuff in it. I tested the drainage of it by filling a 12 ounce plastic cup with a drain hole in the bottom, saturated it, and let it drain. After it finished draining naturally, I could only shake about 3 tablespoons of water out of it. This told me that the double ground bark drains well. I made a large batch of 511, and just assumed I could eliminate the peat, so I made a 5:1, bark-perlite batch. I'm not sure why I added the perlite if the bark alone drains well. I think I was just scared to leave it out. After that, I took a gallon of the plain double ground bark and sifted it with a kitchen strainer to see just how much fine stuff was actually in it. I got just about a quart of fine stuff out of the gallon, which would be 25% 'peat', a little more than Al's suggested amount of 1/6th to 1/7th of the whole for the 511. Since I'm a little nervous about too little water retension because my containers will be in full sun and drying quickly, and the bark alone drains well, can't I just eliminate the perlite also, and go with the straight double ground bark in the containers? Thanks. Ed.

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tapla (mid-MI z5b-6a)

Ed - the double grind is going to compact a fair amount & water retention is going to increase. I think I'd tend to want to retain the perlite as a fraction of the whole. If you decide to eliminate the perlite, I'd urge you to use a wick .... at least until the planting has matured to the point where roots have fully colonized the entire container. When you feel you really NEED some additional water retention, simply pull out the wick and you instantly get that boost. Ain't science fun?!! ;-)

To ease your angst a little: I make my 5:1:1 using a pretty coarse bark & haven't yet had any trouble having to water anything in normal size containers more than once daily. Most containers are watered every 2-3 days, and I tend 2 grow in smaller containers than most growers use.

Al

    Bookmark   April 17, 2011 at 1:19PM
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jojosplants(9/ Tucson, Az.)

I am making my 5-1-1 fairly coarse too. I've eliminated the peat due to the amount of fine material it has. And use the perlite.

Were in the high 80's right now to low 90's and I'm only having to water my tomato's and roses every 2-3 day.

JoJo

    Bookmark   April 17, 2011 at 1:34PM
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edweather(Zone 5a/b Central NY)

OK, thanks. I appreciate the feedback. Will stick with the perlite for now. Am very excited about using the 511 this year for the first time, mostly for tomatoes, but already have some potatoes and peas planted in it. Very curious to see how the peas do. They'll grow in almost anything, so they should do well. The potatoes will probably love it. Didn't lime the potato mix.

    Bookmark   April 17, 2011 at 4:43PM
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tapla (mid-MI z5b-6a)

You'll need to be sure they're getting Ca & Mg, Ed.

Al

    Bookmark   April 17, 2011 at 5:18PM
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jojosplants(9/ Tucson, Az.)

I'm going to try potato's this summer for the first time. Alot will go in the mixes, I really don't have 'garden' space.

JoJo

    Bookmark   April 17, 2011 at 8:55PM
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edweather(Zone 5a/b Central NY)

For the pea mix, I limed it and included a CRF. For the potato mix I included 1 tablespoon per gallon of a CRF with Ca & Mg. I will be using FP for the maintainance of both. That should be enough, right? Thanks. Ed.

    Bookmark   April 17, 2011 at 9:13PM
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margo_k(5)

Yes this sounds interesting, think I will try it. The pine bark I have left over from last year has a considerable amount of fines in it, not sure exactly how much tho. So as a test this year I will mix the pine bark and mix in perlite and skip the peat.

I have arthritis and fairly limited time, so screening the pine bark to remove big chunks, then screening again for fines is difficult. If I can screen once through 1/4" hardware cloth to remove big pieces and use whatever goes through the screen for containers, that will save me time and effort for sure.

I will adjust the mix by adding more perlite for better drainage for plants that need it. And add lime to the mix of course!

Thanks. :)

Margo

    Bookmark   April 17, 2011 at 10:36PM
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margo_k(5)

BTW, I should be using "coarse grade" perlite for the 5-1-1 correct? Much of the perlite I see is very small, but I'm looking for a larger grade. I have seen photos of it in much bigger sizes but so far no luck finding any.

    Bookmark   April 18, 2011 at 8:27AM
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jodik_gw

Coarse grade perlite isn't something I've found locally, either... but perlite is so lightweight, ordering it online and having it shipped shouldn't be very costly, I would think... so I'm probably going that route this year.

The perlite found locally is a bit too small for my taste, and it contains a lot of dust and tiny particles that require removal... not that I mind... I just want larger particles.

Personally, I'd keep perlite as a fraction of a medium mix... mainly for it's weight, but also because it serves as an inexpensive portion of total volume, in my opinion.

    Bookmark   April 19, 2011 at 11:50AM
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margo_k(5)

Thanks for the reply Jodi! The photos I've seen of "coarse grade" perlite look to be about the size of a pea or pea gravel. I've not seen any perlite close to that size locally. Everthing around here seems to be the same thing you have, fairly small particles with lots of dust.

I'll keep looking. I might try a few plants without it just to see what happens.

Thanks again.

Margo

    Bookmark   April 19, 2011 at 1:34PM
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greenman28 NorCal 7b/8a

Margo,
if you have any Hydroponic shops in your area, check with them.
It can be a little intimidating going into a store that is obviously geared toward
indoor marijuana growing, but don't worry: they won't sell you pot, and you won't be
put on any government list :-)

I buy course grade Perlite in 4 cubic foot bags for $20.

Josh

    Bookmark   April 19, 2011 at 1:39PM
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edweather(Zone 5a/b Central NY)

Referring back to my last post in this thread, I decided to add gypsum to the potato mix to make sure there is plenty of calcium available. The CRF I originally used in the mix, at the rate of 1 tablespoon per gallon of mix, has about 1% of Magnesium in it. I will using Foliage Pro at 1/4 strength at every watering. Do I still need to use epsom salts in the water for additional magnesium?

    Bookmark   April 19, 2011 at 8:28PM
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tapla (mid-MI z5b-6a)

.... need to know how much gypsum you added to make an educated guess.

Al

    Bookmark   April 19, 2011 at 11:35PM
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edweather(Zone 5a/b Central NY)

Al, I haven't added the gypsum yet. I purchased it today. Originally when I made the mix for the potatoes I left out the lime, and used 1 Tablespoon per gallon of a CRF which contains 3.5% Calcium, and 1.4% Magnesium, and plan to maintain with 1/4 strength FP. So far, the only Ca and Mg that is in the mix is from the initial CRF. Will this be enough? What would you suggest? Thanks. Ed

    Bookmark   April 20, 2011 at 12:32AM
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jodik_gw

Hydroponic stores would most likely carry a coarser grade of perlite, as Josh suggests, and would be your best bet... I'd Google it and see what you come up with. Orchid growers may also offer bags of coarse perlite, or perhaps even bonsai growers. You never know where you'll locate that needed item... it's like a treasure hunt! :-)

    Bookmark   April 20, 2011 at 5:12PM
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tapla (mid-MI z5b-6a)

I probably would have limed it and called it good, which is what I do for the 5:1:1 mixes I use.

A lot of what we talk about on the forum isn't 'required' to have plants you'll be pleased with. We like having fun squeezing the best out of our plants, and we like having a thorough understanding of the whys/hows of our plant's workings, but in the end, your success failure probably isn't going to hinge on whether you choose lime, or gypsum and Epsom salts as your Ca/Mg source.

Growing well is about reducing the effects of the most limiting factor(s) that influence growth. By far, the factor we see that is most commonly most limiting is that whole soil/water-retention/aeration relationship. For most people, understanding that relationship and getting things favorably implemented propels them forward one giant step. Getting their nutrition supplementation squared away is usually the next largest step. Mostly then, the rest is smaller steps - fine-tuning, so to speak. It ALL matters, and the more you know and understand, the easier it is to justify increasingly better expectations.

AL

    Bookmark   April 20, 2011 at 9:08PM
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