Hi,
I am planning out mixing my own potting soil. This will be mainly for peppers and tomatoes, squash, and some herbs. On hand, I got a bunch of peat moss. Last year I made a mix of equal parts peat, perlite, and compost. I wasn't too impressed with this mix though and want to come up with something better.
Anyway, someone told me I should add vermiculite to my mix too. The way I understand it is that perlite provides better aeration than vermiculite, but vermiculite retains moisture better. Is it worth it having both? Is one better than the other? Last year I used garden compost, which wasn't really recommended for containers. Anyone have a recommended product?
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PunkRotten
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I don't use vermiculite or compost in my potting mix because they both hold too much water.
I use 50% peat 50% perlite. If I do add compost it is vermicompost and only a couple of handfuls to a five gallon bucket. That hasn't caused any problems for me. I use osmocote slow release in my potting mixes. But if I wanted to make it organic, I would just use fish emulsion every two weeks instead. However, my neighbors would complain so I use osmocote instead and only use fish emulsion as a boost once in a while.
I use 50% peat 50% perlite. If I do add compost it is vermicompost and only a couple of handfuls to a five gallon bucket. That hasn't caused any problems for me. I use osmocote slow release in my potting mixes. But if I wanted to make it organic, I would just use fish emulsion every two weeks instead. However, my neighbors would complain so I use osmocote instead and only use fish emulsion as a boost once in a while.
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rainbowgardener
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I use coconut coir instead of peat. It is more sustainable/ renewable, but I also find it easier to work with.
My homemade compost is too heavy and moisture holding for containers, so I use mushroom compost. It is a very nice product, very fine textured. It is very cheap. You can get 40 lbs of it for $5 or less. If you order it on line shipped to a store (not your home), it is free shipping.
I have only used perlite, which I like. This year I will be experimenting with using rice hulls instead of perlite as a more eco-friendly product, but since I haven't done it, I can't say anything yet.
This mix (coir/mushroom compost/perlite) makes a nice potting mix, but it is lower in N than the Miracle Grow type products, so it does need some supplementation. I add whatever fertilizer boost I have on hand - used coffee grounds, worm castings, AACT, alfalfa pellets. Fish products are good, but I have trouble using them with cats around, plants get dug up.
My homemade compost is too heavy and moisture holding for containers, so I use mushroom compost. It is a very nice product, very fine textured. It is very cheap. You can get 40 lbs of it for $5 or less. If you order it on line shipped to a store (not your home), it is free shipping.
I have only used perlite, which I like. This year I will be experimenting with using rice hulls instead of perlite as a more eco-friendly product, but since I haven't done it, I can't say anything yet.
This mix (coir/mushroom compost/perlite) makes a nice potting mix, but it is lower in N than the Miracle Grow type products, so it does need some supplementation. I add whatever fertilizer boost I have on hand - used coffee grounds, worm castings, AACT, alfalfa pellets. Fish products are good, but I have trouble using them with cats around, plants get dug up.
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evtubbergh
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I sometimes use 50/50 spaghnum peat/perlite but I would love to use coir too, we just don't get it here. I find peat moss holds a lot of moisture and shrinks when it dries but the perlite breaks it up very nicely.
The peat moss, being imported from Canada, is stupidly expensive so I use compost from a bag sieved to get the very large bits out in the same way with perlite. I would not use my own compost as it is very heavy, only the bagged stuff, which has a lot of bark and whatnot I can't chop up for mine. I don't even sieve it when up-potting. I find it dries out a little quicker than the peat moss but is very well drained so is better for some things.
Interestingly I have observed the water-holding capacity of perlite on it's own and was very impressed. I poured a cup of water into the tray under a bowl of perlite that had dried out and the perlite sucked it up in moments. I think the capillary action of perlite is very strong but might be broken somewhat by the addition of compost/peat etc.
I am busy planting tree seedlings so I need very well drained medium with decent moisture holding capacity and lots of food. I think I will use bone meal and do regular Seagro applications. I was thinking of using the vermiculite to replace the moisture holding capacity of the peat and do compost/perlite/vermiculite in equal parts. If I pick up some vermiculite this weekend I will try and let you know.
@rainbowgardener the mushroom compost is actually a great idea because it's very rich in manure but has been sterilised so doesn't grow weeds like normal manure does. My mom used to use it but I don't know what happened there. I must go and find out if the mushroom farm is still operating where it used to and get a bag. My poor husband is going to have a heart attack. Thanks
I will just tell him it's your fault.
The peat moss, being imported from Canada, is stupidly expensive so I use compost from a bag sieved to get the very large bits out in the same way with perlite. I would not use my own compost as it is very heavy, only the bagged stuff, which has a lot of bark and whatnot I can't chop up for mine. I don't even sieve it when up-potting. I find it dries out a little quicker than the peat moss but is very well drained so is better for some things.
Interestingly I have observed the water-holding capacity of perlite on it's own and was very impressed. I poured a cup of water into the tray under a bowl of perlite that had dried out and the perlite sucked it up in moments. I think the capillary action of perlite is very strong but might be broken somewhat by the addition of compost/peat etc.
I am busy planting tree seedlings so I need very well drained medium with decent moisture holding capacity and lots of food. I think I will use bone meal and do regular Seagro applications. I was thinking of using the vermiculite to replace the moisture holding capacity of the peat and do compost/perlite/vermiculite in equal parts. If I pick up some vermiculite this weekend I will try and let you know.
@rainbowgardener the mushroom compost is actually a great idea because it's very rich in manure but has been sterilised so doesn't grow weeds like normal manure does. My mom used to use it but I don't know what happened there. I must go and find out if the mushroom farm is still operating where it used to and get a bag. My poor husband is going to have a heart attack. Thanks
I will just tell him it's your fault.-
albopepper
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I'm curious. You mention "I wasn't too impressed with this mix". What didn't you like about it? What results did you find? Too wet? Too dry? Not fertile enough?
This is the mix I used for Peppers in 30 gallon SIP totes:
This mix has been used for a 2nd season already with excellent results. I just had to re-fertilize for season 2.
Coir is nice, but can be pricey. Peat moss is cheaper, but will become hydrophobic if it dries. I say use both. Use your peat moss you already have & add some Coir. Then too, you could use a certain amount of pine bark fines (the dark stuff, but NOT dyed). CHEAP! And great for increasing volume & holding structure.
I think Vermiculite is great. Perlite is good too. But they go well in tandem with each other. Neither can simply replace the other. As silicates, they help to maintain structure & avoid compaction.
I don't advise sand, top soil, or compost. Especially that cheap, crappy compost sold at the chain stores. That stuff is nasty & full of stones & clay. EEK!!! As mentioned, a little vermi-compost is nice. But otherwise, use organic fertilizers to supply the nutrients.
This is the mix I used for Peppers in 30 gallon SIP totes:
This mix has been used for a 2nd season already with excellent results. I just had to re-fertilize for season 2.
Coir is nice, but can be pricey. Peat moss is cheaper, but will become hydrophobic if it dries. I say use both. Use your peat moss you already have & add some Coir. Then too, you could use a certain amount of pine bark fines (the dark stuff, but NOT dyed). CHEAP! And great for increasing volume & holding structure.
I think Vermiculite is great. Perlite is good too. But they go well in tandem with each other. Neither can simply replace the other. As silicates, they help to maintain structure & avoid compaction.
I don't advise sand, top soil, or compost. Especially that cheap, crappy compost sold at the chain stores. That stuff is nasty & full of stones & clay. EEK!!! As mentioned, a little vermi-compost is nice. But otherwise, use organic fertilizers to supply the nutrients.
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rainbowgardener
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Yes, when I have worm castings I add them. I don't buy stuff like that.
This seems like a very nice mix and interesting idea about having a wicking layer and a growing layer. That would be great for larger pots. I don't know about trying to use it with little seedlings in very small containers. It is pretty elaborate and a lot of stuff to buy if you are buying.
I tried the MG moisture control once and hated it. Retained way too much water.
My mix tends to be a little low on fertility compared to the MG potting mix I used to use. So I supplement with whatever I have around - used coffee grounds, alfalfa pellets, worm castings, compost tea (AACT). The plants respond really well to the AACT.
This seems like a very nice mix and interesting idea about having a wicking layer and a growing layer. That would be great for larger pots. I don't know about trying to use it with little seedlings in very small containers. It is pretty elaborate and a lot of stuff to buy if you are buying.
I tried the MG moisture control once and hated it. Retained way too much water.
My mix tends to be a little low on fertility compared to the MG potting mix I used to use. So I supplement with whatever I have around - used coffee grounds, alfalfa pellets, worm castings, compost tea (AACT). The plants respond really well to the AACT.
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PunkRotten
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Basically it wasn't fertile enough and I felt a little more aeration would have been nice too. I will probably pick up some coconut coir and more material for aeration/drainage. But I don't wanna go with perlite because of cost. I may go with pumice stone instead. Any other materials you guys recommend? I havea 15 lb bag of worm castings and plenty of other organic fertilizers. But I'd like to get more worm castings. I paid $20 for the 15 lb bag I got and to me that is pricey. I don't have any lime, but I have azomite. That should work for adjusting the pH correct?
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albopepper
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@rainbowgardener: What I've done in times past, is to wait until MG potting mix goes on sell. I would buy 2 cu ft bags for cheap. Then I would supplement the mix as needed. Part of the supplementation is to add silicates. Part is merely to add volume and reduce cost per container.
The SIP containers are really awesome for full size, annual plantings. Not needed for seedlings tho. Here is my design for the 30 gallon types:
@PunkRotten: 33% Perlite is a substantial amount. Did you buy the 4 cu ft bags? You should be able to get those for $15-$25 per bag. But in my area vermiculite has always been harder to find & more costly as well. Your idea of trying pumice stone sounds interesting. I've never worked with that.
As for azomite vs dolomitic lime, azomite is more for the trace minerals. Dolomite is for Mg, Ca and for raising pH. Just don't use hydrated lime.
To get a boost in nutrients, you could buy something like Espoma Biotone in a BIG bulk bag. Or try making your own cocktail from fertilizer components: Alfalfa Meal, Bonemeal, Dried Blood, Green Sand, Kelp Meal, etc.
If you'd like more worm castings, why not get some red wigglers? Buy a thousand worms & never buy a bag of castings again! That's what I did & I love it!
The SIP containers are really awesome for full size, annual plantings. Not needed for seedlings tho. Here is my design for the 30 gallon types:
@PunkRotten: 33% Perlite is a substantial amount. Did you buy the 4 cu ft bags? You should be able to get those for $15-$25 per bag. But in my area vermiculite has always been harder to find & more costly as well. Your idea of trying pumice stone sounds interesting. I've never worked with that.
As for azomite vs dolomitic lime, azomite is more for the trace minerals. Dolomite is for Mg, Ca and for raising pH. Just don't use hydrated lime.
To get a boost in nutrients, you could buy something like Espoma Biotone in a BIG bulk bag. Or try making your own cocktail from fertilizer components: Alfalfa Meal, Bonemeal, Dried Blood, Green Sand, Kelp Meal, etc.
If you'd like more worm castings, why not get some red wigglers? Buy a thousand worms & never buy a bag of castings again! That's what I did & I love it!
Coir isn't that easy to come by in quantity here either, and it is a lot more pricey than peat moss. I did try it but found that it help much more water than peat moss. I don't use vermiculite because it is harder to come by than perlite, holds more water than perlite and costs almost 50% more than perlite.
I did try to add compost to my potting mix and I did buy the cheap supersoil potting mix which has compost in it, but neither worked out well. In fact, the supersoil killed everything. It even had fungi in the package.
I tend to overwater, so I need a fast drying mix. If I add a couple of handfuls of vermicast to the peatlite, it does not affect the way the potting mix dries. When I tried to make 1/3 peat most 1/3 compost, 1/3 perlite it held too much water. While it meant I could water every other day, if it rained or I watered every day, I had very high death rates from dampening off. The water would sit on top of the mix in the pot and take a while to drain.
I tried 1/4 peat moss, 1/4 compost and 1/2 perlite. It was better but still held too much water for too long. I also used the compost made locally from greenwaste and that was probably not the best choice. The pH of that compost is pH=7.8. It still made a heavy potting mix.
Finally, I went back to peat lite and only added a couple of handfuls of vermicast to a five gallon bucket. It worked out best. I get the benefit of the vermicast without affecting the water holding capacity of the final mix.
I did try to add compost to my potting mix and I did buy the cheap supersoil potting mix which has compost in it, but neither worked out well. In fact, the supersoil killed everything. It even had fungi in the package.
I tend to overwater, so I need a fast drying mix. If I add a couple of handfuls of vermicast to the peatlite, it does not affect the way the potting mix dries. When I tried to make 1/3 peat most 1/3 compost, 1/3 perlite it held too much water. While it meant I could water every other day, if it rained or I watered every day, I had very high death rates from dampening off. The water would sit on top of the mix in the pot and take a while to drain.
I tried 1/4 peat moss, 1/4 compost and 1/2 perlite. It was better but still held too much water for too long. I also used the compost made locally from greenwaste and that was probably not the best choice. The pH of that compost is pH=7.8. It still made a heavy potting mix.
Finally, I went back to peat lite and only added a couple of handfuls of vermicast to a five gallon bucket. It worked out best. I get the benefit of the vermicast without affecting the water holding capacity of the final mix.
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applestar
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I have been using pumice stone sparingly. For me, it was an experiment with some reservations about cost and carbon footprint of shipping since it isn't a local source, but I wanted to compare it with man-made heat processed (harzerdous to breath dust) perlite.
I found it works very well for drainage and micro pore biosphere. One major difference is that pumice stone significantly increases the weight. It threatened weight capacity of my seed starting shelves and made larger containers more difficult to move around.
I want to turn my attention more to pine bark -- are "pine bark fines" sold as such or do you have to screen them out of some other package? (I was able to buy small chip pine bark a couple of years ago but couldn't get any last season -- I have a large bag of chunky pine bark mulch and I have been using smaller pieces out of it) Pine bark would tend to be acidifying?
I have also used chicken grit (ground oyster shells) in the past for calcium/alkaline mix though I didn't get any this past season. I have been advised to use turkey grit (which I think is ground granite or other kind of rocks?) which I intend to explore as well.
I found it works very well for drainage and micro pore biosphere. One major difference is that pumice stone significantly increases the weight. It threatened weight capacity of my seed starting shelves and made larger containers more difficult to move around.
I want to turn my attention more to pine bark -- are "pine bark fines" sold as such or do you have to screen them out of some other package? (I was able to buy small chip pine bark a couple of years ago but couldn't get any last season -- I have a large bag of chunky pine bark mulch and I have been using smaller pieces out of it) Pine bark would tend to be acidifying?
I have also used chicken grit (ground oyster shells) in the past for calcium/alkaline mix though I didn't get any this past season. I have been advised to use turkey grit (which I think is ground granite or other kind of rocks?) which I intend to explore as well.
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gillespieza
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Here's my 2 cents about the difference between vermiculite and perlite:
They are both good for aerating soil mixes, however, they have completely different behaviours with respect to water retention. In a nutshell, vermiculite retains more water for longer, than perlite.
Vermiculite is made from expanded mica (kind of like popcorn), and its very good for aeration since it has large particle sizes and its "poofy" and spongy. It absorbs water and holds on to it like a sponge - plant roots can then absorb what they need as they need it, and the surrounding soil remain sort of moist-ish.
Perlite, on the other hand, retains water because it has a large surface area - many cracks and crevices that water can cling to. But it drains much more quickly than vermiculite.
So, if you have plants that like a consistently moist soil, or are particularly thirsty (eg, strawberries, tomatoes, etc), I'd use vermiculite. On the other hand, for plants that like being "very well drained", like cacti/succulents that like to dry out between waterings, then perlite is a good choice.
Oh, also, perlite tends to get washed out of containers sometimes - at least in mine, it keeps floating to the top of my containers and then it blows away once its dry
@imafan - wow, its fascinating the different in pricing across the world - in Cape Town, vermiculite is much cheaper than perlite, and easier to find, and coconut coir is about a third of the price of peat moss (and also easier to find)
@evtubbergh - have you looked at Game for coir? My local Game always stocks compressed bricks of the Starke Ayres brand of coir - I think they call it Peat on the label, but its actually coconut coir. I prefer to get mine at my local Stark Ayres nursery though - they sell unbranded compressed bricks for half the price of their own branded bricks. R17 for a brick, uses 10L of water to uncompress. Compared to R100 for a small bag of peat moss.
@PunkRotten I've had great success in containers using: 1:1:1 compost (or mushroom compost):coconut coir:vermiculite but don't forget to feed regularly since the nutrients drain out of containers very quickly.
They are both good for aerating soil mixes, however, they have completely different behaviours with respect to water retention. In a nutshell, vermiculite retains more water for longer, than perlite.
Vermiculite is made from expanded mica (kind of like popcorn), and its very good for aeration since it has large particle sizes and its "poofy" and spongy. It absorbs water and holds on to it like a sponge - plant roots can then absorb what they need as they need it, and the surrounding soil remain sort of moist-ish.
Perlite, on the other hand, retains water because it has a large surface area - many cracks and crevices that water can cling to. But it drains much more quickly than vermiculite.
So, if you have plants that like a consistently moist soil, or are particularly thirsty (eg, strawberries, tomatoes, etc), I'd use vermiculite. On the other hand, for plants that like being "very well drained", like cacti/succulents that like to dry out between waterings, then perlite is a good choice.
Oh, also, perlite tends to get washed out of containers sometimes - at least in mine, it keeps floating to the top of my containers and then it blows away once its dry
@imafan - wow, its fascinating the different in pricing across the world - in Cape Town, vermiculite is much cheaper than perlite, and easier to find, and coconut coir is about a third of the price of peat moss (and also easier to find)
@evtubbergh - have you looked at Game for coir? My local Game always stocks compressed bricks of the Starke Ayres brand of coir - I think they call it Peat on the label, but its actually coconut coir. I prefer to get mine at my local Stark Ayres nursery though - they sell unbranded compressed bricks for half the price of their own branded bricks. R17 for a brick, uses 10L of water to uncompress. Compared to R100 for a small bag of peat moss.
@PunkRotten I've had great success in containers using: 1:1:1 compost (or mushroom compost):coconut coir:vermiculite but don't forget to feed regularly since the nutrients drain out of containers very quickly.
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PunkRotten
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albopepper
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@gillespieza: I know what you mean about perlite drying out and blowing away. A layer of mulch works great for this. I've used a thin layer of vermicompost or also pine bark fines. Helps with moisture & temperature fluctuations too.
It's amazing... The scope of techniques we use around the world varies so greatly! The cost of certain additives. The local availability. The climate. What works great for one gardener may be very impractical for another.
I like it.
It's amazing... The scope of techniques we use around the world varies so greatly! The cost of certain additives. The local availability. The climate. What works great for one gardener may be very impractical for another.
I like it.
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PunkRotten
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albopepper
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I have not tried lava rocks. Not sure how those would work.PunkRotten wrote:Are lava rocks good material to use in potting mix? The ones I saw are very porous and the size of marbles some slightly bigger. How about bark or wood chips? Is there a recommended size and type?
As for bark / wood chips, do not use the chips. Don't use wood from heart wood or sap wood. Use only dark, shredded bark. I recommend pine, 1/8" to 1/2" pieces. Partly composted is ideal.
Heart or sap wood will draw too much nitrogen from your mix as it tries to break down. Pine bark has less cellulose, and more lignin. Lignin is slow to break down, and so nitrogen is not quickly depleted.
Pine tends to be more acidic. Hardwood will give you more of an alkaline soil. So keep that in mind, depending on what you want to grow. Brassicas in a pine / peat based mix might have issues with club root if you don't pH test and adjust as needed. That's why people so often include dolomitic lime.