Does baking soda affect hydrangeas?
Written by
Nguyen Minh
Reviewed by
Prof. Martin Thorne, Ph.D.Baking soda can affect hydrangeas by raising the pH of the soil toward alkalinity, which may cause the blooms to turn pink. Still, its effects are temporary and unpredictable. The sodium hurts the soil structure, and I ruined a hydrangea bed with it before "discovering" the real means.
Temporary pH Effect
- Raises pH for 2-4 weeks before neutralizing
- Requires frequent reapplication for minimal change
- Rainwater quickly washes away baking soda
Soil Damage Risks
- Sodium accumulation causes salt crust on soil surface
- Compacts soil reducing root oxygen and water absorption
- Kills beneficial soil microorganisms over time
Color Change Inconsistency
- Fails to maintain pH above 6.5 consistently
- Produces splotchy pink blooms rather than uniform color
- Doesn't provide calcium or magnesium for plant health
If you must use it, at least do so intelligently. One tablespoon dissolved in a gallon of water applied to established plants every six weeks, foliar depression immediately after application to prevent burning, hardly produced more tingeing with me than proper amendments.
Use dolomitic rather than calcitic lime for the best pinks. This will slowly raise the pH level without adding sodium to the soil. Dolomitic provides the necessary calcium and magnesium as well. Apply a cup per ten square feet yearly. My pinks became truly pink only after the change to dolomitic lime.
Catch baking soda damage early. If you see white salt crusts on the soil or yellow edges to the leaves (salt burn), or notice that your plant is stunted and seems to be struggling somewhat, you have root damage from excessive use of sodium bicarbonate (baking soda). Give the soil a good flushing with rainwater or distilled water. I have saved many plants in this way after inadvertently using too much baking soda.
For "true" pink results, do this: prove the pH of the soil. Then spread dolomitic lime in early fall. Use high-phosphorus fertilizer next spring. Water plants with a good sprinkle of tap water. Write things up each month. Besides saving face, you'll be saving the soil.
Read the full article: Soil pH for Hydrangeas: Color Control Guide
