Question
Thank you, but I have mulch around it, and it gets watered correctly.  It is happy and healthy and adding new growth, but the flowers which were blue when I bought it are now green.  Any other ideas?  Does it need acid or alkaline?  Help.
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Followup To

Question -
Just a quickie.  Why are the flowers on my Hydrangia green?  I'm sure it just needs something added to the soil, but I don't know what.  Thank you.

Answer -
Some hydrangeas have green flowers naturally, but that is rare. I suspect your hydrangia is not being fertilized and the care is not good. Green flowers is more a sign of the flower never developping properly.

Mulch well around the hydrangeas and water regularily and deeply (use a soaker hose). If planted in too hot sun (such as hot afternoon sun) and the plants droop, then it will never flower properly. Also if it is too crowded by other plants, the same can happen.

Otherwise, make sure it gets atleast half day (morning) sun in northern areas. Contrary to common belief, hydrangeas are not shade plants. They prefer protection from hot afternoon sun, but should not be in too deep shade or the flowers may not develop properly. If the plant is watered, but the leaves droop in afternoon sun, then it gets too much sun. If not, then it is fine.

Apply a 10-10-10 fertilizer twice in spring and early summer.

Answer
Ok, I now understand. The flower has withered. This happens to the flowers when they have been on the plant for a while. The flowers do not last the entire season. Once green, you can cut it off (deadhead) but do not remove too large part of the stem as this is where the new flower buds reside. Your flower is finished for this year.