I think the soil acidifier made the soil acid or more acid. The soil can have amendments added to the first 4-6 inches. Use the soil acidifier or aluminum sulphate or sulfur if that is not available to keep those flowers remaining blue. Lime will make it pink and raise the pH. The hydrangeas are getting the available aluminum in the soil and this determines the flower color on those hydrangeas that can change color. The white flowered ones do not change color with the pH fluctuations. Why clear away the mulch? This mulch eventually decomposes and also feeds your plants. The fresh mulch is great if only to act as a weed block;replenish it where the sun has disintergrated it and the mulch also it acts to improve moisture retention so you don't have to water as frequently. I would leave the existing mulch and add to it if needed. Why give yourself more work? The fertilizer does not change the pH of the soil it just feeds your plants. I would feed the hydrangeas as they are starting to leaf out in the spring.

Dont replace the old mulch, the older it gets the better it is for your soil -- making it richer. As the mulch decomposes through time, your growing hydrangea will love that. Just add more each year to keep up with the weeds.

The only reason I was removing it was it was a big hard block, all stuck together and nasty. We had a bit of a slug problem, not sure if that was the culprit or not. We had it brought in by the truck load the last two years and I dont know if there was something living in it but by spring it was like cement with white spores on it. It didnt look healthy enough to keep. I guess I should have stated that. sorry This year I just went to Home depot and bought some bags of it.
Should I incorporate some Hollytone into the top 4 inches of soil? I thought in order for them to be blue, the soil had to be acid and in order for it to absorb the acidity it needed alum. sulfate. I thought I was doing everything right. There are so many differing opinions.. add coffee grounds, iron nails, cider vinegar, etc. I re-read Dirr's book and still was confused. Do i need to add hollytone AND alum sulfate? ( I say Hollytone because I have A lot of it here from Holly Bushes)

Thanks for the help

Mellyz,

Hollytone is a great organic fertilzer and will go a long way toward 'helping' to maintain/promote acidic soil. Alum Sulfate is not a fertilizer, just a chemical additive for blueing. If your bed has high ph, both may be necessary. If you have a large bed, this can be very costly and labor intensive as you will have to do it on a regular basis in order to maintain blueing ph levels. Keep in mind that if your water has high ph/lime, you are fighting the Hollytone and Alum Sulfate every time you water the plants......yg

The peat moss combined with the aluminum sulphate was probably what caused the soil to test acidic. But soils will always tend to revert to their original chemistry over time to so to maintain acidic soils for your hydrangeas, you will need to continue to add an acidifying agent. That could be peat moss, agricultural sulfur, cottonseed meal or a fertilizer for acid lovers, like the Hollytone. Use the aluminum sulphate sparingly to increase the blueness and only after you have successfully increased the soil acidity - too much aluminum can cause toxicity.

Thanks guys once again you answered my question. =-)