If your hydrangeas wilt or dry out, construct a shade to block the sun during the afternoon. You can also try using mulch. If the winter forecast predicts unusually cold or prolonged frost, or if you are planting in a lower than recommended hardiness zone (see above), you may need to provide winter protection for your hydrangeas.
The varieties named Enziandom, Kasteln, Merritt’s Supreme, Red Star, and Rose Supreme all have the ability to be grown as pink or blue blossoms, although they vary in intensity.
Alternatively, you can also create blue blossoms by applying a fertilizer that is low in phosphorus and high in potassium. Look for a 25/5/30 fertilizer blend. You’ll also want to avoid superphosphates and bone meal. [5] X Research source
Apply a fertilizer that contains no aluminum, but high levels of phosphorus, which inhibits aluminum uptake. Look for a fertilizer that contains a 25-10-10 blend. Consider raising the pH by adding wood ash or crushed limestone to the soil, as this also makes aluminum uptake difficult. Avoid raising the pH higher than 6. 4, or the plant may develop health problems.
