Don't use Gypsum.

Use dolomite lime, 1 Tblsp. per gallon of 511 mix.

Mix it in when you wet mix the bark, peat and perlite. Do this a couple weeks before you plan to use the 511.

I've never added any lime after the initial mix, I just went by the suggestions given on this site for the 511 recipe.

Maybe someone else can chime in about adding more lime over time.

This is what I use. Make sure it says dolomite lime on the package.

Would the lime make the potting mix too alkaline for conifers and Japanese Maples?

Read the responses IN THIS THREAD:

I've never grown JM's before so didn't dare say 511 would be fine for them, that's why I linked to a thread that said gritty mix and 511 would both be fine for them (along with some home grown recipes). Although I've grown several types of deciduous broad leaf seedlings in 511 and they did great.

I've noticed that too, most pre-mixed potting mixes say 'Lime added to adjust ph' on the ingredient label.

The 5-1-1 IS perfectly fine for JM's. I'm not sure where the acid pH requirement came into play for them, but it is not at all restrictive. Slightly acidic soil is fine but they will also grow happily in neutral to slightly alkaline soils as well. What IS critical is good drainage. That is why both the 5-1-1 and the gritty mix are so highly recommended for these if growing in containers.

is this for permanent growing in the pots??? .. or long term at least ... long term in the tree time sense???

if not.. im wondering why you even need it?? .. the mix or the gypsum ....

ken

If anyone is asking about either the 5-1-1 mix or the gritty mix, it is because they are growing the trees or shrubs in containers. There is no reason one would use those mixes for an inground gardening situation - highly unnecessary and far too expensive!!