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My neighbor swore by using coffee grounds on my hydrangeas for blue blooms.
Tried it for a whole season. The soil pH barely shifted and the flowers stayed pink. Anyone know a more reliable method for acidifying soil?
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jordancarr21d ago
Coffee grounds break down way too slowly to change pH in a single season. For real results, you need to use elemental sulfur or aluminum sulfate. The sulfur is a slower, longer term fix, while the aluminum sulfate works faster because it adds aluminum the plant needs for blue color. Just be sure to follow the package rates closely, because over doing it can harm the plant. A soil test first is the best move to know exactly how much to add.
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jamesf2921d ago
Wait, aluminum sulfate adds aluminum for blue color? That's wild, I always thought it was just about the pH change. Does that mean if your soil already has aluminum, you might not need as much? Kinda makes the soil test even more important, lol.
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