Hydrangeas acid-loving claims are only half true since these shrubs handle a wider pH range than most acid plants. They grow well from pH 5.0 all the way up to 7.0. This makes them much more flexible than strict acid lovers like blueberries or azaleas.
I tested this on my own bushes by changing their soil over two years. My pink blooms turned deep blue once the hydrangea soil pH dropped to 5.5. The shift took time but the results were worth the wait. Now I can pick what color I want by how I treat the dirt around each plant.
The hydrangea color change comes from how the plant uses aluminum in the soil. In acidic soil below pH 5.5, aluminum stays free and roots can take it up. The plant moves this metal into its blooms where it makes blue color. In sweet soil the aluminum gets locked up and you see pink instead.
Bob Vila notes that this color trick only works on bigleaf types. The one you find at most garden shops is Hydrangea macrophylla. Its big round flower heads can shift from deep blue to bright pink based on nothing but soil chemistry. This gives you power over how your garden looks.
Bigleaf Hydrangea
- Color response: Shows the most change with blue in acid soil and pink in sweet soil based on aluminum.
- Best pH range: Grows well from 5.2 to 6.5 but you need pH below 5.5 for true blue blooms on most plants.
- Popular types: Endless Summer, Nikko Blue, and most mophead or lacecap types fall into this group.
Panicle Hydrangea
- Color response: Blooms start white or cream and fade to pink as the season goes on no matter what pH you have.
- Best pH range: Very flexible from 5.0 to 7.5 which makes them great for tough spots in your yard.
- Popular types: Limelight, Little Lime, and Quick Fire all do well in most garden soils.
Smooth Hydrangea
- Color response: Pure white blooms that do not shift with pH at all since they lack the color changing trait.
- Best pH range: Happy in pH from 5.5 to 7.0 with good health at most normal garden levels.
- Popular types: Annabelle and Incrediball both have huge white flower balls that stay white all season.
White hydrangeas stay white no matter what you do to the soil. They do not have the genes that let bigleaf types change color. If you want white blooms, pick a smooth or oakleaf type and stop worrying about pH. They look great without any special soil work.
In my experience changing colors takes at least two seasons to see the full shift. You can add sulfur for blue or lime for pink around your bigleaf bushes. Work the stuff into the top few inches of soil in early spring. Test your pH in fall to see how much change you got.
The hydrangea soil pH you pick should match what color you want to see. For blue aim below 5.5 and keep adding sulfur each year to hold that level. For pink push above 6.5 with lime. Purple blooms happen when you land right in the middle around 6.0 to 6.5.
These shrubs do fine in most garden conditions. You don't need to stress about pH unless you want to control the bloom color. Plant them where they get morning sun and some shade in the afternoon. Good water and decent soil matter more than hitting a perfect pH number.
Read the full article: 10 Acid Loving Plants for Your Garden
