That will be one for the books, as they say. I know they are acidic but I never thought of doing that / using them for that. It probably depends on how acidic they really are, if the bacteria/yeast combination can somehow do something unexpected or attract unexpected visitors (dogs, cats, deer, squirrels, bunnies, etc), stuff like that...

If no one that has done this chimes in, try with one hydrangea (do the usual sulfur/aluminum sulfate or the others); see what happens and how fast the problem is corrected for both cases. Then post your results...

Good luck, Kristen. Luis

If you want more acidic soil, you need to decrease the pH, not increase it. A higher pH is more alkaline......a lower pH more acidic.

What is the current pH of your soil now?

a couple of months ago I also had some yellowing leaves on 1 of my macrophyllas (in pots)..I put some Milorganite on it to give it some iron..after awhile it looked much better..was it a lack of iron?..or did it just need fertilizer?..I know the soil in Indianapolis is alkaline but I haven't had a soil test..my blooms were pink which indicates alkaline soil..I've never tried to change the pH..

Thanks for all the tips!! Here is what they look like. I added some soil acidifier a couple months ago around the base but my issue is that they are underneath my roof that extends beyond the porch so they don't get direct rain onto them and instead I water them with a soaker I planted underground. Thoughts? My hydrangeas were so beautiful last year and were not so this year.

That's pretty severe chlorosis or an iron deficency caused by insufficiently acidic soil. You can use chelated iron to bump things up or alter (lower) the soil pH. One is fast and the second takes time. And is much longer lasting.....iron chelate is only a temporary fix.

Since your plant will be dropping its leaves soon, I would work on lowering pH. If you start now, when the hydrangea leafs out again in spring, it should be showing normal growth and coloring. Sulfur is the most efficient way to lower soil pH but you really do need to know what the pH is now before you start playing around with it.

Soaker hose is a good solution to watering them when the roof helps keep them dry. I suspect that the cement in your house is also leeching lime and making them get a double dose of alkalinity (from the cement and from the soil). Since they are so affected by the lack of iron, I would use the iron-chelated liquid compounds first as they help fix things faster, albeit not as fast as I or you would typically want but stilll faster than the non-liquids. Then after a month or two of applying them then either continue with them or switch to the non-liquids since they last a tad longer and can be reapplied longer.

You can get soil samples analyzed by mail or get a soil ph gadget to measure the soil pH yourself; units that give the result in numbers are more useful but these may be difficult to buy locally at the end of the growing season... may have to buy by mail instead if you cannot find them at stores.

Since they are sooo whiteish, I would get started with some liquid "acidification" asap.