I've had the same hydrangea bushes for about 5 years and they always turned blue in my acidic soil, but this year they're staying pink no matter what. I've added sulfur and even checked my soil pH which is still around 5.5. Is something wrong with the plant or am I missing something?
your hydrangeas might be experiencing nutrient lockup or aluminum availability issues even though your soil *looks* acidic on paper. the pH is only half the battle - aluminum (which is what actually creates that blue color) needs to be soluble and present in your soil in the first place. sometimes after years of adding sulfur or other amendments, you can accidentally create conditions where aluminum gets bound up and unavailable to the plant, even in acidic soil. also check if you've been using any fertilizers high in phosphorus, which can actually interfere with aluminum uptake and shift things toward pink 😅
the other sneaky culprit is that hydrangeas get less responsive to soil amendments as they age. younger plants are way more flexible with color changes, but after 5 years they sometimes just... decide what they're doing and stick with it. if you've kept consistent care, the plant itself might just be settling into a pink phase regardless of chemistry. try doing a soil test through a local extension office (not just a home kit) - they'll tell you if aluminum levels are actually there or if something else is blocking uptake. if the test looks fine, you might need to accept the new pink era or consider replacing one bush with a newer variety that holds blue better in your conditions 🍄
Have you noticed any changes in how much sun those bushes are getting over the past year or two? The thing is, aluminum availability does matter, but there's a simpler culprit that often gets overlooked: as hydrangeas mature, they sometimes shift their color genetics and just won't respond the same way to soil chemistry anymore, especially if the plant is getting more afternoon sun than it used to (trees grow, neighbors trim branches back, etc.). More light can lock in pink pigments regardless of pH. Before adding more sulfur, which won't help if that's what's happening, walk around and honestly assess whether the planting spot gets more direct sun now than it did five years ago.
I've seen this happen with established plants - sometimes they just stop responding the way they used to, and it can be frustrating when the soil chemistry checks out. One thing worth digging into is whether those bushes are getting stressed in other ways, like inconsistent watering during hot spells or root competition from nearby plants that weren't there before. Also, older hydrangea stems can lose some vigor, and newer growth sometimes produces different colored flowers even in the same bush. Have you noticed any pest damage, branch dieback, or changes to the leaves themselves - things like spotting or stunted growth? That might point to whether this is a soil thing or the plant telling you it needs some TLC elsewhere.
The pH reading isn't actually telling you the whole story here - soil chemistry is weird that way. Even at 5.5, if your soil is older and depleted, the aluminum that causes the blue color might not be staying available to the plant, especially if you're not adding other amendments alongside the sulfur. But before you go down the chemistry rabbit hole, check whether anything's changed with how the plant's being watered. Hydrangeas that shift from blue to pink often do it because they're stressed or getting inconsistent moisture, which messes with nutrient uptake way faster than soil pH drifting. If the watering's been steady, a soil test that checks actual nutrient levels (not just pH) would tell you way more than what you're measuring now.
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