Answer: Hydrangeas can be slow to leaf out so being tardy shouldn't be a concern. However, you should notice some nice, plump buds on the stems. If the buds look brown, they may have started to develop and then got nipped by frost. You can check to see if they're alive - just snap a bud off and see if it's green inside. If it is brown, it's dead. The stems should develop healthy new leaf buds in a few weeks. Or, if the stems died, too, then you'll see new growth from the base of the plant. If this happens, your hydrangeas probably won't bloom this summer but they should bloom next summer.
It is much easier to change a hydrangea from pink to blue than it is from blue to pink. Changing a hydrangea from pink to blue entails adding aluminum to the soil. Changing from blue to pink means subtracting aluminum from the soil or taking it out of reach of the hydrangea.
That said, I'll give the best information that I have on this subject and let you take it from there.
For hydrangea blooms to be pink, the plants must not take up aluminum from the soil. If the soil naturally contains aluminum, one must try to keep it away from the hydrangea's system. Following are a few tricks that might work:
Add dolomitic lime several times a year. This will help to raise the pH. Shoot for a pH of about 6.0 to 6.2 (If it goes above 6.4 hydrangeas may experience an iron deficiency). Since hydrangeas take up aluminum best at lower pH levels, raising the pH will help to keep the bluing effect of aluminum out of the hydrangea's system.
Use a fertilizer with high levels of phosphorus. Phosphorus helps to prevent aluminum from creeping into the system of the hydrangea. Choose a fertilizer close to the ratio of 25/10/10 (Phosphorus is the middle number).
In areas that naturally produce blue hydrangeas (soils with aluminum), consider growing pink hydrangeas in large pots. If hydrangeas are grown in pots, it would be best to use soil-less mixtures, since these mixes would probably not have aluminum in them. In a pot, it will be much easier to control the requirements for growing pink hydrangeas.
Best wishes with your hydrangeas!
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