One of the most popular types of hydrangeas to grow in the Kansas Garden is what we refer to as the macrophylla hydrangeas. These hydrangeas are the ones that produce the very showy blue and pink flower buds. They’re also persnickety. As gardeners, we need to learn how to manage those plants.
First of all, when it comes to the macrophylla hydrangeas, we have to understand how they bloom. Many of the old varieties have been on the market for years, and the most popular one is a variety called Nikko Blue. It blooms on old wood. So during the summer months, a shoot is produced, and a flower bud is set. Then, it goes through the winter, and the next spring it comes into flower in June.
The problem with the older types of macrophylla hydrangeas is that the flower buds aren’t winter hardy. So, if there is a harsh winter, the buds will be killed, and you’ll end up with a green bush. Gardeners will go to a lot of work trying to protect those flower buds. They may wrap the whole bush in chicken wire and fill it full of leaves, or they may wrap it in burlap, which is full of leaves.
But for many gardeners, that may be too much work to get a showy bloom. Luckily, scientists have bred new varieties that can set flower bud on both old and the new growth that is produced during the current season. They are commonly known as the Endless Summer flowering hydrangeas. That’s because they bloom on the old and the new wood.
This group of hydrangeas has opened up a whole new world to the gardener because they don’t have to protect the plants in the winter to get them to bloom in the summer. But, they still take some special care. In Kansas, they require a constant supply of moisture. And they also prefer to grow in morning sun and afternoon shade. If you put them into too much shade, they won’t flower. And, if you put them in too much sun, the needs for watering will be too high, and they’ll scorch. However, they’re very easy to grow as long as you provide even moisture, a constant supply of fertilizer, and then you’ll be able to get blooms during the spring and summer months based on when the new growth is set.
One of the interesting things about the macrophylla hydrangeas is the flower color. Some bloom blue, some bloom pink, and some bloom a pinkish to purple to mauve color. This difference in flower color is based on soil pH levels. If you have a pink flowering hydrangea, it means you have an alkaline soil – above pH 6.5.
If you have a blue flowering hydrangea, it means you have a more acidic soil. The way you change the pH is based on the color you desire. Blue is the most prized color for the gardener. Pink in Kansas is easier because our soils tend to be naturally high in pH. Usually, when you plant a macrophylla you’ll get a pink bloom. To lower the pH for a blue bloom, the first thing you’ll need to do is get a soil sample. You can have the soil tested at K-State Research and Extension. First, you’ll start lowering the pH by adding sulfur to the soil. So, instead of just digging a hole for the new plant. You may want to plant it in a bed. A box that is five by five or a six-foot area will work well where the hydrangea is going to grow. You can change the pH by incorporating the sulfur.
I’d also recommend organic matter such as compost or peat moss to help loosen the soil. Then, to maintain that color of blue throughout the growing season, and in the years to come, you’ll need to apply sulfur or aluminum sulphate. That will help keep those flowers blue. Of course, when the plant blooms, you’ll know if you added the correct amount of sulfur to the soil. For a blue hydrangea, you’ll need to add sulfur yearly. The amount is based off the soil test analysis.
In summary, macryphylla hydrangeas are the most fussy to grow in Kansas. They’ll need proper watering, proper fertilization, morning sun, afternoon shade, and flower color will be dependent on the soil pH. But, they’re great additions to the garden as they bloom in summer to bring much joy to the garden.
This feature story prepared with Dennis Patton, Kansas State University Research and Extension Horticulture Agent, Johnson County. For more information, visit your local county extension office or visit our website at KansasGreenYards.org.