How to Grow Blue Hydrangeas: Soil pH, Varieties, and Care Tips

The Science of Color

Only certain hydrangeas (macrophylla types: mopheads, lacecaps) change color based on soil pH. Acidic soil (pH 5.2–5.5) yields blue; alkaline soil yields pink. White varieties never change.

Achieving Blue Blooms

• Test soil pH.
• Lower pH with aluminum sulfate (2 tbsp per plant), acidic mulch, pine needles, or pine bark.
• If soil is strongly alkaline, blue may be impossible—consider container growing with controlled mix.

Shopping Reality

Names like 'Nikko Blue' or 'Forever Pink' indicate potential, not guarantee. Bloom color depends on your soil, not the label.

Maintenance

Monitor pH annually. Mulch with acidic materials. Water with rainwater (tap water can be alkaline). Fertilize with low-phosphorus formula to aid aluminum uptake.