gritty mix bark size question (w/picture)

12 years ago

Hello All,

Today I purchased a couple bags of pine bark fines. I have a question on what to use and what to exclude.

In the picture below, the top material is the bark that passed though 1/4" hardware cloth but did not pass though 1/8" hardware cloth. I think this is ideal, and it compares well with the material on the right (fir reptile bark) which is what I used for my first batch.

However.... a LOT of material is going to waste. The material at the bottom of the photo is the stuff that fell though 1/8" hardware cloth, which I then sifted though fiberglass insect screen to remove the super fine dust type stuff. Material of this size represents the largest percentage of what is in the bag. If you were me, would you be comfortable including this material with the material at the top of the photo to make the gritty mix, or would you discard it?

As an aside, nothing is actually being "discarded", I'll use this for mulch or something. A 2cf bag was under $3 so my biggest concern isn't cost but merely the amount of effort it will take to get such a small amount of usable product if I decide to only use the material at the top of the photo.

Thanks!!!

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Comments (7)

tapla (mid-Michigan, USDA z5b-6a)
12 years ago
What are you combining the bark with - screened Turface & Grit, or something else? What size are the other particles?

Al
irun5k
Original Author
12 years ago
Al, this will be combined with screened turface & crushed granite.

Either in a 1:1:1 or a 4:3:2 ratio as has been suggested over in the plumeria forum.
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Hey Al, just wanted to make sure that 2 years later all this advice is current. Some of my gritty mix is now just about 2 years old also. It seems to be holding up but I got to thinking, like some of those in this thread, that it sure would be nice to have a permanent mixture for the long term plantings, by withholding the organic ingredient. Plus it's one less ingredient to have to buy and later screen. I see your main purpose for including it was to lessen the fears of potential gritty mix users that plants couldn't possibly grow in it. It's also used to average the particle size and water retention of the two other ingredients. I use FP to fertilize and look after my plants often enough that this isn't a fear of mine. I utilized a 1:1 ratio of Cherrystone:Turface for two basjoo banana trees planted in the ground here in zone 4. I have heavy clay and when I grew them the last time, they grew slow and their corms later rotted over the winter. I also don't think I properly watered/fertilized. So this year after reading your posts in the link below, I upped the FP by 4x to 1 tsp of FP per gal, rather than 1/4 tsp I used before, and brought the PH down to 5.5 with vinegar rather than the unacidified 7 of my tap water. I know you water with this dosage weekly with outdoor plants but I watered with it almost every day during the hot summer days with no apparent issues. I found that this amount of FP was too much for the indoor plants though... I also experimented with digging about a 4-5 gal hole where I planted the bananas and poured in the 1:1, so at least some of the soil near the corm and roots didn't have to deal with the heavy clay. The plants grew waaay faster this summer and hopefully it'll help the stems/corms survive this winter. I utilized the 1:1 before reading your post in this thread about using a higher ratio of granite/cherrystone to compensate for the small particle size of the turface. Even though the basjoo's did great in the 1:1, I'm guessing in a pot, a proper ratio (2:1 or 3:2 like you mentioned) would be a bit more important. Is this a safe assumption? Here is a link that might be useful: Fertilizing advice
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I've been using a 50:50 base mix of perlite/ turface for many years. You can easily modify this mix for different needs. Most mesembs benefit from the addition of a clayey component. For me, I just dig beyond the topsoil in my yard for some good dirt. I also substitute perlite for some lava rock and small pebbles. It's a heavier, longer lasting mix which works when repotting infrequently for mesembs. This same mix is my preference for small cactus species like Aztekium, Blossfeldia, tricky mamms like luethyi, etc. "bigger" plants like some Crassula, aloes, aeonium etc. you could add more perlite to lighten big pots. It also makes it safer to leave outdoors all spring/summer/fall with rain. My palms, plumeria and cycads live in this mix too. Floating perlite is not an issue. But it does easily displace with high water pressure like from a hose. Some form of fertilizer is a must. I'm also a fan of submerging small pots with small plants into bigger, deeper containers to help stabilize root temperatures. Practically any healthy plant I've ever had to repot always has roots circling the bottom. I really don't understand the concept of shallow or regular pots. I think the deeper the better. I haven't really noticed any exception. For some species it's mandatory. Haworthias, many cactus plants with tuberous roots. Even Lithops which tolerate a shallow home will grow much better in very deep pots. Pleiospilos too. For anyone unsure or unconvinced, try an experiment. Take a pot with any plant you want, and bury it into much deeper pot for a growing season. Pull it out later and see what you find. Bury an Aloe, pachypodium or most any strong Echeveria or similar in the garden and watch it take off. We would all be great at bonsai, plenty good experience with root constriction and limiting growth lol!
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I think you're right to consider there are essentially no sub-1/8" fines in the prescreened fir bark, like there would be in most pine bark products. I think the answer to that fact lies in an understanding of the concept behind the soils, which is essentially based on the use of a high % of chunky material, with only enough fine material to provide water retention enough to satisfy the grower. With a little experience, we'll be able to look at the bark fraction, and decide how much peat and perlite is appropriate. In the end, we want to be certain we don't add enough peat to go beyond the threshold point, so all of the large air spaces between the chunky material are full of fines. I can temper what I said by adding, as we move toward formulations that are less and less water retention, it's easier to keep the plant appeased than the grower. A plant can be perfectly happy if growing in a medium that actually requires watering twice per day, perhaps even happier than in a medium that actually needs watering every two days. The grower might not be as impressed as the plant in a soil that requires watering twice daily, but it's important to also realize that increasing water retention beyond a certain point is a limiting arrangement. Perched water is limiting, so the more there is of it, the greater the loss of potential. Being familiar with the concept that governs water retention puts the grower in control of that relationship between water retention and limitations. IOW, you get to decide how much potential you're willing to sacrifice for extended intervals between waterings. Al
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Lately I've been doing a lot of thinking about bark and I agree with Andy that it's not necessary for cacti and succulents. The only use I see for bark is to help hold nutrients and water. Numbers below are Cation Exchange Capacity (CEC), which is essentially how much nutrients something can hold: Bark is around 50 meq/100g. Turface is around 35 meq/100g. Grit is essentially zero. Perlite is essentially zero. So if you add more Turface and use less/no bark, things should work out just fine. At least, that's my scientific justification! Honestly, my first pots with gritty mix weren't that great and I didn't really know what ratios would suit my plants or growing conditions. 1:1:1 is a pretty broad recommendation and perhaps an oversimplification. I also didn't realize how important sifting and particle size was (hint: extremely!). Now that I have a better idea, I have the following components ready for mixes. Normally, I just use the top two items: 5 gallon bucket of "pre-mixed gritty mix". 1-2 gallon pail of grit (for customizing mix for specific plant species). 1 gallon bucket of sifted large perlite. Bag of blended-sifted repti bark. 5 gallon bucket of C&S soil (primarily as part of soil for plant gifts). 1 bag of horticultural sand (unused, why did I even buy this?) Lots of details, but making a good mix and having a plant do well is really satisfying. =)
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tapla (mid-Michigan, USDA z5b-6a)
12 years ago
If you want to use it, I would use a wick to help drain any excess water. The whole purpose of the gritty mix is to build a soil that holds it's water INSIDE of particles instead of between them. Reducing particle size creates a perched water table, so you almost might as well use the 5:1:1 mix. I'm offering that observation purely from a practical perspective.

If you do use a wick to help get the benefits from a fully drained soil, you can just remove the wick once the planting has matured & roots have colonized the soil mass. At that point, air will return to the whole soil mass quickly enough that the short duration of soggy soil won't likely have a significant effect.

Al
irun5k
Original Author
12 years ago
Al, thank you for your comment. I decided not to use the finer material- in the end I decided there is no need to pollute my mix with substandard material.

This is what I ended up with from 2cf of material... the top is what is usable, the left is too coarse and right is too fine. It is amazing how little of the material turned out to be usable. However it is very hard to find around here. So I can buy this for $2.50 a bag and do a lot of work or pay $20 for a 1cf bag for reptile bark and still end up discarding a portion of it. I will keep looking to see if I can find something else but for now these are the two options I have available so far.

Thank you again.

{{gwi:3454}}
tapla (mid-Michigan, USDA z5b-6a)
12 years ago
A lot of people would gladly take the leavin's for the 5:1:1 mix ..... ;-) Do you grow veggies or mixed display containers?

Al
irun5k
Original Author
12 years ago
Hi Al, yes I have several things that might like the 5:1:1 mix. From what I've read, I would use 5 parts of the fine material (stuff that fell though 1/8" cloth?) If so, I assume I should still screen out the dust.

Is there any use for the more coarse stuff (> 1/4") in any container mixes? I've know seen it used in the nursery medium that bougainvilleas come in. As an aside, I actually think bougainvillea would love one of your mixes, but most folks claim their roots are extremely sensitive and recommend not disturbing them *at all*... so I've been reluctant to repot and remove old soil. But I digress..

Thanks,
Brian
penfold2
12 years ago
I don't know if this helps you, but I use the coarse bark for my epiphytes, mainly orchids and aroids. Bromeliads might appreciate it too. These mixes are all coarse material, though. If you tried to mix in finer particles like Turface, they may migrate to the bottom of the pot.

gritty mix bark size question (w/picture)

Comments (7)

tapla (mid-Michigan, USDA z5b-6a)

irun5k
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gritty mix bark size question (w/picture)

Comments (7)

tapla (mid-Michigan, USDA z5b-6a)

irun5kOriginal Author

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tapla (mid-Michigan, USDA z5b-6a)

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tapla (mid-Michigan, USDA z5b-6a)

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