Answer: Regular potting soil is generally neutral in pH. Since your pink hydrangea has already bloomed it won't be necessary to sweeten the soil at this point. Next winter you can begin to change the soil pH so that as the flower buds form they will react to the alkalinity of the soil and bloom pink.
You can grow Endless Summer in a large container, moving it up to the next larger size as it matures. Enjoy your hydrangeas!
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