Kitchen Garden Forum

I have a couple of sacks of Vermiculite particles (I think!) from a tank insulation. What can I use them for in the garden? Suggestions gratefully received!

I use fine vermiculite to cover seeds as it's nice and light it also marks I out the row, but I would be careful to make sure exactly what you have and test it out first on something you don't mind risking.

Might be worth a simple Ph check before use, making sure that the water you use in the test is neutral

Dear John,
this insulation vermiculite is not suitable for use in Horticulture as it will have been treated with a water repellent. Construction rock wool is also treated. The reason may have something to do with the following story.
I once heard about a grower who being a little careful with his money who thought he could save a bob or two and filled his bungalow loft with used horticultural grade rock wool bales to insulate it. All was well until something sprang a leak and soaked all the bales very thoroughly. When he went out of the door one day and slammed it the vibration was enough to bring down every ceiling in the house! Suffice it to say his wife was NOT amused and neither was his insurance company!!!
Regards Sally Wright.

On a similar theme I've often wondered what would have happened if a colleague had a fire. He boxed in his hot water cylinder with plywood then gradually filled the void with those odd shaped lumps of packaging expanded polystyrene.

sally wright wrote:this insulation vermiculite is not suitable for use in Horticulture as it will have been treated with a water repellent.

Are you sure about this. I have bought several times vermiculite in large packs, both for horticulture and insulation, and it never has any mention of treatment. The only grade is by particle size, and it is sold as suitable for insulation, horticulture, vivariums, etc. It all seems to absorb water very readily.

Hi Sally,
Years back I ordered some Vermiculite suitable for horticulture and they delivered the very large grade by mistake and it had to go back and the correct grade delivered. I was told then that had I used any of it it would not have made any difference because it was only graded by size.
Now I will admit that this is probably 20 years ago and things might have changed but personally I would not use the larger grade had I been able to make it smaller because the application needs to be an even coat and it would not matter how much faffing about you did you could not acheive the right size.
I have used Perlite for preference most of the time.
JB.

Dear All,
according to the Wikipedia and the UK vermiculite association pages I checked before I wrote my previous post; loose fill insulation vermiculite is commonly treated with a water repellent to prevent damp problems. However it might be that not all brands are so treated; the one I came across when we were insulating the back wall of our glasshouse when the roof was off was.
Thus if you wish to buy insulation grade vermiculite for use in horticulture I would offer this caveat; check the bag, check with the vendor and check the brand's website. I personally would consider it foolish to use builders vermiculite as a seed covering over £1000 worth of seeds (which is on average what I sow in any given year) without checking it out very thoroughly just to save £20-30. As a further point I may not know what the water repellent is but I am certain I do not want to eat anything grown in it!
Regards Sally Wright.