What a glorious summer for big leaf hydrangeas (Hydrangea macrophylla). They seem to be everywhere! Most of us haven’t seen our flowers since 2013 yet the plants kept on growing. Some gardeners even forgot about them. Now come the questions. Here are some of the most common ones from the past few weeks.
How come everyone else has tons of flowers and my plants have only a few?
The most common reason is pruning at the wrong time. You shouldn’t prune this plant at all unless it has gotten too big for its space or you need to remove dead, diseased or crossing branches. If you must prune, stop after August 1 and don’t do it again until you see all the leaves unfurl in spring and are sure which stems are dead and have no flowers at their tips. If pruning isn’t your issue, then you have given your plant too much nitrogen or water, both of which cause it to make leaves instead of flowers. Or your plant didn’t get enough sun. Yes, they do need some sun. Morning sun is best.
How can I change the color of my flowers? IF your plant is one which can change its color, then you need to work on the pH of the soil where the roots reach. Blue flowers are produced when aluminum in the soil can be used by the plant and that happens when the pH is below 5.5 (acidic). Pink flowers are produced in the absence of aluminum so work to achieve a pH of 6.2 (alkaline) or higher. Your local garden center can help you find the right products to do this along with a soil testing kit.
Why are there different colored flowers on my plant? It is simply a case of uneven acidity in the soil where the roots are living as seen in this photo of ‘All Summer Beauty’ . Also as the flowers mature and get their final color, they sometimes morph into that color. You may actually see some green along the way.
When do I prune my plant? Ah, the age old question. Hydrangea macrophyllas, even the rebloomers, produce their flowers on growth from the prior year (old wood) and the current year (new wood). That means that you need to stop any cutting by about August 1 unless you want to risk losing next year’s flower buds which will be produced from then on. You are essentially in what I call the “hydrangea danger zone” until the following season when your plant has completely leafed out and you can determine which stems have tips with viable buds. Then and only then should you cut your plant. But then why would you cut it anyway unless you have it in the wrong place?
How do I feed my hydrangea? Hydrangeas love rich humusy soil. Compost is their best friend so an annual top dressing of organic compost is the best thing you can do for them. . It works nice and slow, helps the plant retain moisture, and encourages beneficial soil microbes.
Let’s hope Mother Nature is good to us over the next 12 months so we get two consecutive years of hydrangea enjoyment. By then you’ll be able to reap the benefits of your newly upped hydrangea IQ.
By Lorraine Ballato