Soil and peat floating

As stated above.

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Perlite has no nutritional value. It is predominantly made of silicon dioxide with trace amounts of potassium, sodium, iron, magnesium, and calcium; however, perlite is not soluble and thus the nutrients are not available to the plant. It is used solely to improve drainage.

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It can be done if layered in the mix when running living soil methods. You want the drainage and air of perlite throughout. This is a must and additional added to maintain 1/3 of soil volume.

The vermiculite is only added into a small 3-4” layer up top to retain constant aerated moisture, reduce compaction and buffer upwards. It must be soaked overnight to expansion and then mixed into compost, or soil medium without the additional perlite added. The reason, this is the area that needs to stay consistently moist to sustain max biodegradation. A mulch layer is then added.

If this is not your intent, it is best to avoid.

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I do 20% by volume, but I can see where more makes sense. Perlite is way less expensive than soil by volume.

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20% makes sense when you’re using a premade mix that already contains some.

This seem to be more soil building than buying premade so 1/3 volume

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I’ve always done Happy Frog with 20% by volume perlite. Happy Frog is probably 5% perlite at best. Dry cycles are super important, especially for young plants. I’m with you. Adding more isn’t a bad idea.

So i can top dress with vermiculite to get slow realese of silica?

Can i use leca or bark instead of perlite?

That will drain N from medium to sustain decomp. Not recommended. Also, the only thing to replace perlite is pumice or lava. 10% BioChar could account for part of the 1/3 aeration.

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Silicon dioxide is not bioavailable to plants. Silica products typically come in the form of potassium silicate.

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Thank you for your information :grin: really helps alot.

Thank you! Learnd alot today :sunglasses:

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I only have peat and perlite at home, peat at 4,5-5 pH, i have some dolomite lime, you think it would work to buffer up the medium with dolomite lime?

Peat is acidic as it decays, so it doesn’t surprise me. Correct, pH can be buffered with lime, but do not expect the addition of lime to move the pH up much all at once.

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Do i need to top dress or put it in the solution?

Lime should be mixed in the grow media when the pot is being set up before planting.

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Thank you so much!

Don’t use vermiculite full stop. It’s not suitable for growing plants and is primarily used as a medium to germinate seeds. Once the seedling has a couple of sets of true leaves, it’s taken out of the vermiculite and put into potting mix.

Note on vermiculite. It has a fine dust in and this can damage your lungs if you inhale it. Some sources of vermiculite are found in association with asbestos and this can cause cancer if you inhale it. Asbestos was a serious issue with vermiculite back in the 1960s, 70s, 80s and 90s and is significantly less common today, but there’s no guarantee it doesn’t contain asbestos. So try to avoid using vermiculite and if you have to use it, make sure it’s wet before handling and wear a dust mask to reduce the chance of inhaling something bad. It may not have anything bad in it, but spending a few dollars on a dust mask is a good investment to prevent possible lung cancer.


If you want to use perlite, then mix 10, 20 or 30% perlite with 70, 80 or 90% soil or coconut coir. A 70/30 mix (70% coconut coir or potting mix and 30% perlite) is the most common for cannabis. You measure the perlite by volume, not weight. Get a plastic pot and take 3 scoops of perlite and 7 scoops of potting mix or coconut coir and mix them up in a container, then use that to fill pots for your plants.

Before handling perlite it needs to be wet. Perlite has a very fine dust in it and that dust can damage your lungs. A new bag of perlite should have some small holes poked in the bottom of the bag and then a small slit cut in the top of the bag. Put a hose in the top of the bag and turn the tap on a little bit. Wash/ wet the perlite while it’s in the bag and let the water drain out the holes in the bottom. I tend to fill the bag with water and then let it drain out. Do this on the lawn so the dust goes into the soil. When the bag had drained you can handle the perlite reasonably safely. Just don’t handle perlite if it’s dry.


If water is pooling on top of the potting mix, the soil/ mix has become hydrophobic (repels water). To fix this get some wetting agent granules/ powder from a plant nursery or hardware store and sprinkle it on the potting mix or mix it into the potting mix. Then water it in. Wetting agents are basically soaps that remove biofilm and oils that build up on potting mix and stop them absorbing water. Wetting agents have a neutral pH (pH 7.0), unlike soap and washing up liquids that have a very high pH (above 9.0). A neutral pH is better for the plants. A very high pH can burn and kill the roots of plants.

Wetting agents normally only need to be applied once but if the potting mix dries out for a month or more, you will probably need to reapply it. Regular watering (several times a week) should stop potting mixes becoming hydrophobic and needing a wetting agent.

If potting mix is constantly wet and doesn’t drain freely, that can be caused by a bad potting mix, or lack of drain holes in the pot, or too much water too often. Cannabis plants need good drainage, and wet/ waterlogged roots will kill the plant. Make sure they have really good drainage.

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I though this was nonsense when I read it. It’s not, though the mine is no longer active.

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Don’t think everything is safe and free of asbestos either. China shipped a container load of brake pads to one of the car companies (Toyota I think it was) in Australia a couple of years ago and they had asbestos in. Asbestos and asbestos products are banned in Australia and have been since last century (like most parts of the world), and China refused to take them back saying they don’t import asbestos products.

There are other dangerous and carcinogenic substances still being widely used too. Bifenthrin is a pesticide and often sold as ant powder or ant sand. It was banned in most countries a few years ago because it kills everything in the animal kingdom, yet it can still be bought in a lot of countries.

Glyphosate (roundup) is another carcinogenic substance that gets sprayed around by councils and governments. It kills everything in the plant and animal kingdom and it leaves a carcinogenic residue behind after it has been sprayed. That residue can last for at least 6 months after it was sprayed. Roundup has recently been found on grains that we eat and is from farmers growing roundup ready gm crops made by Monsanto. The farmers broad-acre spray their crops 2 weeks before harvest to remove weed plants. Then they get a cleaner harvest (cleaner meaning few weeds in). The drawback is the roundup in our food.

Just be careful using anything that might have dust in or that is imported from third world countries because they don’t always have good quality controls, and their quality control is usually worse for products they export.

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