I buy three types of potting mix, these are:-
Native potting mix for my lemon myrtles, and lillipillies
Azalea potting mix for my blueberries, and camellia sinensis (tea plant)
General purpose potting mix for everything else
I mix in coir, sand, rock minerals, vermiculite etc for all of them before using.
It would be too troublesome for me to lower the PH myself so it’s easier just to get specialised potting mix, but is the native potting mix necessary? I understand most natives don’t like phosphorus, but how much phosphorus are there in the general purpose mix since I get the cheapest available anyway?
Does anybody grow their natives in containers, and what do you use as growing medium?
This may help with potting mix for natives, and I did not know about aging the pine bark chips.
Not sure about native pine trees (eg Cypress) but I read a lot of exotic pine trees give out an exudate from their roots to keep other plants from growing close. Extrapolating (guessing) that some of that stuff could be in the bark - certainly fresh pine bark smells faintly resinous - composting it would break down the substance/s making the bark a sterile produce.
My natives are growing in the unmodified and un-fertilised soil. As are the natives over the back fences - hundreds of years old gum trees and others.
El cheepo potting mix does not contain fertiliser - the $3-4 a bag stuff doesn't anyway. So it would be safe to use with potted natives.
Potting mix may contain toxic waste there is a composting facility at the Gold Coast who applied for a development permit and in the documentation was permit for what could be added to compost sandblasting sand and landfill leachate where a couple of toxic substances if you compost 100,000 tons of green waste by adding small amounts of toxic waste the end product when tested is legal .In Europe they had a problem with liquid egg used in commercial cooking dioxin from oil that was used for chicken food that was contaminated and they claimed it was safe to consume because the level was lowered from mixing with unaffected liquid eggs.