I admit it, I love hydrangeas. Old-fashioned garden stand-byes, the beauty of a hydrangea in bloom is unparalleled. What I love best about hydrangeas is the way the blooms age. Rilke reflected on the aging flowers in his poem “Blue Hydrangea”:
Just like the last green in a color pot
So are these leaves, withered and wrecked
Behind the flower umbels, which reflect
A hue of blue only, more they do not.
Reflections are tear-stained, inaccurate,
As if they were about to cease,
And like old blue notepaper sheets
They wear some yellow, grey and violet,
Washed-out like on a children’s apron,
Outworn and now no more in use:
We contemplate a small life’s short duration.
But suddenly some new blue seemingly is seen
In just one umbel, and we muse
Over a moving blue delighting in the green.
Translation © by Guntram Deichsel, 2003-12-03
Hydrangea is a genus of 70 plus species of flowering plants native to southern and eastern Asia. There are two basic flower forms: mop head and lace cap. Mop head flowers are large round flower heads resembling pom-poms or, as the name implies, the head of a mop. In contrast, lace cap flowers bear round, flat flower heads with a center core of subdued, fertile flowers surrounded by outer rings of showy, sterile flowers.
Hydrangea flowers can range from blue to pink, depending on the acidity of the soil. Soils with a pH of 5.5 or lower are acidic enough to allow the aluminum ions to turn the flowers blue. Therefore, if you prefer your hydrangea blossoms blue, add aluminum sulfate to the flowerbed. Before you try this be sure the plants near the hydrangeas can tolerate aluminum, as well.
If you’d like to have pink flowers, you need to add dolomitic lime or a fertilizer high in phosphorus. This doesn’t make the soil truly alkaline, but rather raises the soil pH to 6.0 or higher so the hydrangeas can’t get to the aluminum in the soil.
Hydrangeas grow beautifully in the Bay Area. They prefer part sun or light shade, rich soil with good drainage and plenty of water. Generous mulching helps to keep the roots cool and aids in water retention. Hydrangeas grow well on the north side of buildings and under trees.
In our area hydrangeas tend to bloom in early to mid summer, but the blooms are extremely long lived and can often still be seen at Thanksgiving. Clients often ask when is the right time to prune off the aging blossoms, and I tell them to wait until winter, because those dusky tattered flowers are like old lace, delicate and poignantly reminiscent of summer.