I’m seeing Endless Summer Hydrangeas with both pink and blue flowers. Why is that, and how do I get mine to stay blue?
The color of the hydrangea flower depends on the pH of the soil and the availability of aluminum. With lower pH, the natural aluminum in the soil becomes more available to the hydrangea, which is what makes the flowers turn blue. A more alkaline soil ties up the aluminum, making it not available, and the flowers stay pink. So your goal is to create an acidic soil around your hydrangea. You can do this by adding Pine Soil Conditioner when you first plant, as well as using it as mulch. This helps to lower the pH. Adding coffee grounds around the plant helps lower pH, and, by adding aluminum sulfate in the spring and fall to the soil around the plant, you’ll also be lowering the pH, as well as adding aluminum to the soil – all helping to get those flowers to turn blue. And if you get it just right, you’ll have both colors!
When I prune the dying flower heads off my Endless Summer Hydrangea, do I prune them off at the next leaf node or all the way to the ground?
Prune above the next or next lower leaf node. Pretty much the same with all the hydrangeas, deadheading just below the spent flower on lower leaf node.