Question
In August of 2008 I transplanted a blue hydrangea.  This year it bloomed with pinkish flowers rather than blue.  My soil is somewhat clay.  Can I get them to bloom blue again?  What do I need to add to my soil to accomplish this?  Thank you.   Karen

Answer
Dear Karen

Thank you for your question.

I think you must be growing Hydrangea macrophyllia "Hortensia" (mophead hydrangea) or "Lacecap". The color of this variety of Hydrangea is very much dependent on the soil type. Acid soil produces blue flowers and alkaline soil produces pink flowers!

If you purchase a soil testing kit you can determine how far on the acid side you soil is - if it turns out that it is only just into the acid zone you might be able to influence the color of your plant with the application of a 'blueing compound' which you should be able to get from a garden center.  You would have to keep applying it though!  Why not just go with the pink - pink's pretty!!