How to Prune Tri-Color Hydrangea

Q. I have a tri-colored hydrangea bush in a pot in the front of my house.  When is the right time to cut it back and how do I do it?  After almost 20 years I finally got beautiful flowers on it last spring. After looking it up on the internet, I think I’ve been cutting it wrong.  I’d like your thoughts on this.

A. Wow. You are adventurous. Hydrangea is certainly not a desert plant. It does not like a lot of heat, low humidity or intense sunlight. It does like filtered light or early morning light and humidity. Just what people would tell you NOT to grow here. Go for it!

            If you have evaporating water somewhere with no wind it should like the spot if it’s not too sunny. It will also not like wind. You have to have a balance in the amount of light. Not enough light and the plant will not bloom. Too much light and it might cause leaf scorching, dieback or death.

            It is also interesting because in many hydrangea the flower color may change depending on soil acidity. It is assumed it is because of the availability of aluminum. If there is ever a plant that will test your ability as a gardener, this should be tops on the list. It is probably a wise decision to plant it in a container.

            Tricolor is referring to the color of the leaves, not the flowers. The leaves are supposed to be a combination of green, light green and creamy color. There has been mislabeling of this plant in the past. Whenever you see a tender plant with leaf colors like this it is nearly always one that you must keep out of direct sunlight during the heat.

            My understanding is that Oak leaf and tricolor are pruned the same way. My understanding is that tricolor blooms on older wood, not this past year’s wood. This means that when you prune you will want to keep your older wood established and remove any older wood that is getting too old or that may be crossing or too close to other productive stems.

            The idea is to maintain older wood and selectively removing wood that is too old while constantly renewing the older wood. This will also mean you will have to remove excess new growth that makes the plant too dense and thick while, at the same time, keeping new growth that you want to preserve for future flowers. Not an easy task and certainly one that is difficult to explain. I hope this helps.