Ask The Expert: This is the first time I’ve tried to grow hydrangeas in pots; they are actually doing very well. My first plant was purple that I bought in April, the color now is a greenish color, (very beautiful color). I also have a light pink (called white spirit) and burgundy color. How do I keep the color purple, pink or even blue? What plant food is best, and anything else that keeps my hydrangeas beautiful in pots.  Thank You for your help in this matter. -Juanita

Flower Shop Network Plant Expert Reply: Juanita,

Eventually you will need to re-plant the hydrangeas in the ground. I am assuming that you have Mophead hydrangeas (Hydrangea macrophylla). These types of hydrangea bloom-colors are controlled by soil conditions, specifically the pH of the soil.

• To keep a hydrangea pink you would amend the soil with lime.
• To keep it blue you would use aluminum sulfate.
• Purple blooms are usually the result of a more neutral soil pH.

This would be done in late winter or early spring.

Once a bloom has formed, you can not change or control the color. So, at this point you don’t need to do anything. However, as the bloom begins to decline (which they all do) the color may change to a lighter pink or blue. Some varieties will change to a light greenish or dusty pink color towards end of the bloom life.

As for fertilizer, feed them once or twice during the summer with a slow release fertilizer. I recommend something with a balance ratio like 10-10-10 or 14-14-14. You local garden center nursery will have this product.

Hope this information has been helpful. Please let me know if you need assistance with anything else.
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