Yes, Art, pH has a definite impact. Unfortunately, soil alkaline enough to lock up phosphates is also likely to be highly buffered, and so difficult to make more acid. In a direct assault on high pH, try applying a weak vinegar solution--1 ounce per gallon of water, 1 gallon of solution per foot of plant diameter--each month. Sulfur pastilles may also have an effect, and only need to be applied twice a year. A better approach may be to increase the "humate" content of the soil. "Humates" (actual humates, fulvates, and olmates) have little direct effect on the pH, but can effectively "chelate" phosphate and micronutrient ions, making them more available to plants. "Humates" are available from nurseries in various forms, but you can make your own by making well-aged manure or peat moss tea. I've found the commercial products to be faster acting, but the home-made stuff has other biological benefits, too.

Good luck!
Kevin : )

Thank you Kevin.
I use to have access to leonardite but
that has gone away. My fertilizer I use has greensand(Glauconite) and humate in it. I will continue down that path.
Art

Do you drink coffee? I use the spent grounds as fertilizer. It's a good way to recycle, it's natural, and it's acidic. Plus, it's apparently full of nitrogen and other goodies. My sister says her roses improved dramatically using this cheap trick! If you don't drink it, I'm sure most coffee shops will gladly give you some.

Voodoobrew:
I don't drink coffee but we have a starbuck's close by.On my way home I occasionally stop in and get what they have and add it to my compost pile. I also use it on my Citrus trees.I use the needles from our christmas trees at work to keep my Salvia guarnitica happy.
Art

Is that why my Salvias are so happy? They grow close to my Austrian pines, so plenty of pine needles available and the soil is great! They add some acid but not too much.

Are all coffee grounds equal in nature? I mean, do the flavored ones pose any potential problems?

Susan

susanlynne48:
Your Salvias location in Oklahoma are probably benefiting from shade and acidity both.
Art

Thanks, Art. I aspire to grow Salvias like you do!

Susan

I'd avoid the soil P binding issue altogether by using a seaweed foliar spray. Otherwise, I'd add well-composted organic matter for the reasons Kevin listed, which can be mixed with the coffee grounds. But if you go too far with excess N, xeric sages suffer.

Amen to that, dicot! I am now veerryy cautious about how I feed my S. dorrii!

Kevin : 0