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HOW DO I INCREASE THE ACIDITY IN SOIL FOR AZALEAS?

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  • 1 month ago

    Coffee: coffee grounds have a low acidity level, around a soil pH of 6.8 per Starbuck’s. So, they will not lower soil pH much. They do add nitrogen and that can help reduce the soil pH just as if you were also adding organic compost or composted manure. It is probably more useful to use regular black coffee and cold water, mixed 50-50. Works fast. Ok for small pots but not practical for large areas.

    Vinegar: mix a cup of vinegar and 1 gallon of water. Not practical for large areas.

    Iron sulfate: useful in clay soils. Fast as it relies on a chemical reaction. Faster than elemental sulfur. Use it in a rush or use iron-chelated liquids.

    Elemental sulfur – relies on a biological reaction. Most practical in very large areas.

    Iron chelated liquid compounds – fast acting but needs to be reapplied more often. Not practical for large areas.

    Aluminum sulfate: Is fast acting too but, given in large enough doses, it is also toxic to azaleas and rhododendrons. So, not recommended for azaleas.

    Note: my soil normally has pH of 7.6. I add a layer of organic compost in Spring around the Encore and Kurume Azaleas and the flower beds. This lowers my alkalinity, which the azaleas tolerate; they –knock on wood- have yet to suffer from iron chlorosis.

    Note: Azaleas are not fertilizer hungry plants like roses so, once they are established in the garden in 1-3 years, I let them feed off the decomposing mulch that I put around them; maintain 2-4” of organic mulch –no rocks- year around.

    All these products will need to be reapplied on an on-going basis.

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  • Mr.357
    Lv 7
    2 months ago

    Aluminum sulfate is the go to.  Vinegar can work too .

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  • patty
    Lv 6
    2 months ago

    acid fertiliser

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  • 2 months ago

    A side dressing of agricultural sulfur will work.

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  • 2 months ago

    Every year I have to lower the pH of the soil around my hydrangeas in order to continue to get their magnificent blue flowers. I have tried different soil acidifiers and have found that 'aluminum sulfate' lowers the acidity most effectively. I get mine at Amazon. One bag lasts me about 3 years of applications for 6 hydrangea plants.

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  • Anonymous
    2 months ago

    I put coffee grounds around mine . 

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  • Barry
    Lv 5
    2 months ago
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