Moss and Bleach

I use it at about 50% diluted with caustic soda to kill moss and other growth on my drive and patio.

If you are going to use chemicals to do it you might at least use the right ones. Anything else will be almost a waste of time. Likewise if the conditions are right for moss and lichens they will quickly return.

"Wet and forget" is about the simplest to use.

That is probably a lower concentration version of BAC50.

I prefer to use biological washing powder, cheaper and just as effective, also kinder on other things in and around the garden.

...is the right answer. I use four times the normal (washing) concentration and apply it via a watering can. It's cheap, cheerful, and effective. The moss I bumped off last October has just started to make a much-weakened re-appearance, which was very easy to re-treat. I doubt I'll see it again until November.

For small areas or difficult-to-reach areas I use the same dilution in a used trigger-pack.

According to the MSDS, yes it is, single active ingredient Benzalkonium chloride 68424-85-1 < 10 %

What would you reckon that works out as grammes of Bio Washing Powder to a litre of water?

PA

Just sprinkle the biological powder over the moss. You can wait for rain or mist it. Don't go hard on the hose or you'll just wash the powder into the drains. Good for at least one year or more I.M..

Only you have the data on which you based your statement, Spike.

PA

What amount of powder do they suggest for use in a washing machine? How much water does the machine use for a main wash? The rest is simple arithmetic...

I use liquid bio as we have some, and it's easier to mix, but you could sprinkle the powder on directly, and either very lightly damp it or wait for it to rain.

Well, the data is that a 4x concentration of liquid bio watered onto driveway moss made it go away, apparently mostly permanently.

I got the idea from a post on here late last year, which spoke of builders who had replaced flat roofs, spreading powder bio onto the chippings in order to prevent moss growth for a period of up to five years.

I hadn't got any powder bio to hand, and in any case didn't want my tarmac surface covered with it, so decided to experiment by applying a solution as described. In practise, about 10 percent of the moss recently started to reappear, which was easily zapped with a hand-sprayer of the type I mentioned.

Perhaps a 5x concentration might have killed it all, and if any returns in Autumn I might try that.

Isn't washing powder dangerously slippy on paths made from York stone?

Thanks, I've give it a go.

PA