What element is needed to turn Hydrangeas blue? Is it sulfur or aluminum?
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2 Answers
You want to acidify your soil, so sulfur because that is used to make sulfuric acid.
answered Apr 2, 2019 at 21:48
If you just want blue hydrangeas (Hydrangea macrophylla only) in pots, then a dose of aluminium sulfate will do the trick quite quickly. Either that or sequestered iron will do it, but in the ground, it's harder, because substances applied to the soil will only have a temporary effect - sulfur will need to be added frequently, and it takes a long time to make a difference; frequent use of aluminium sulfate is not recommended - used too often, aluminium can build up in the soil and phosphorus levels can be reduced. More general information re acidifying soil here https://www.rhs.org.uk/advice/profile?PID=82
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couldn't you bury a few old batteries to lower the PH, or is that too quick? Commented Apr 4, 2019 at 16:17
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@black thumb No idea, but I wouldn't recommend it - lead contamination over time is highly likely.– BambooCommented Apr 4, 2019 at 18:26
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1Soil contamination is not only a problem when you're growing food, its an environmental problem generally. other creatures that live on this planet, including the microscopic ones for instance. The general environment is far more important than human beings...– BambooCommented Apr 4, 2019 at 22:29