Moss

[KarlR]

I never sterilise my soil and very rarely have any problems with moss, though algae usually appear in about half my pots after two or three months when I use the baggie method. I usually remove all the pots from their bags within two or three months anyway though, so it's not really a big problem. If I use a propagator for sowing I usually have even less problems with moss or algae as the atmosphere is less moist than in a bag. For the likes of Blossfeldia and Aztekium I keep them in the bags as long as possible, though I'll sprinkle sand on the surface if moss or algae start growing and that'll usually give me another month or two before I have to take them out of the bags.

As I said I never sterilise my soil and have only little experience with microwaving soil, but if you're putting pots filled with soil saturated with water in the microwave (you don't mention watering the pots after microwaving them), I believe you'll have to microwave them for a longer time because of the high water content. I'm fairly sure I've read that the time needed to kill off most or all spores and whatnot increases quite a bit if the soil is very wet.

[DaveW]

Sterilisation times:-

http://www.colostate.edu/Depts/CoopExt/ ... terile.htm

You can make the soil toxic by overheating too:-

"Heat the soil to at least 180° F; keep at this temperature for 30 minutes. Do not allow the temperature to go above 200° F. High temperatures may produce plant toxins."

"Many heavier soils and soils containing large amounts of organic matter may release toxic compounds when heated too long or at too high a temperature. These toxins can cause poor seed germination, plant growth abnormalities or plant death. The toxicity is caused by an accumulation of ammonium compounds, soluble organic compounds, minerals or salts that may occur during the heating process."

[Bob Sobelman]

how many times have i written if you dont want moss cover the seeds with basalt powder. this after you cannot get manco-d
which i use i treat the soil with this in a water solution and let the soil dry out no moss. i buy the basalt sand from companys that sells all kinds of gravels for the tile industry i buy it in sacks of 20 kilo then sift it using just the powder to cover the seeds. NO MOSS

[JoelR]

Interesting thank you Bob. Just purchased a bag of basalt rock dust volcanic fertiliser:

http://www.amazon.co.uk/gp/product/B00Q ... ailpages00

I agree that the sterilisation mustn't be enough. Maybe it is the water content in the soil but I will try the rock dust on a new batch and I'll can apply some to the surface of already affected pots.

[Peter]

Perhaps I'm lucky, but I don't get moss and have never sterilised pots or compost. However I do ensure the compost drains well and never allow it to get soggy.