Greenscape Gardens Green Blog

HYDRANGEAS

Hydrangeas are one of the most popular landscape shrubs since they are so remarkably colorful in bloom. They adapt to a multitude of locations ranging from sunny to partial shade. The hydrangea also tolerates poor soil conditions but thrives in fertile well drained conditions. This plant is an excellent addition to any landscape and will compliment any shade garden plantings.

The big leaf hydrangea (Hydrangea macrophylla) is the colorful shrub we desire in our landscape. This is the species from which the majority of the familiar cultivated hydrangeas are derived. In the past, big leaf hydrangeas bloomed on the previous season's growth. Now the newer cultivars bloom on last year’s growth as well as this year’s growth. For best results, place in a protected site with fertile, moist, well-drained soil. Selections which have proven well in the St. Louis area include:
• All Summer Beauty Large heads of blue or pink, blooms
all summer. Blooms all summer.
Blooms on current season's wood
• Endless Summer Large heads of pink or blue, blooms
on new or old wood. Flowers all
summer.
• Glowing Embers Large fluorescent pink to red flowers
on a compact plant.
• Nikko Blue Large deep blue flowers.

But there’s more! Hydrangeas are a wonderful group of summer blooming shrubs with several other species that bloom well in the St. Louis area.

One of the most durable and reliable of the hydrangeas is smooth hydrangea (Hydrangea aborescens). This 3 to 5 foot shrub flowers freely from June to September. The flowers are rounded and change from an apple green to creamy white during the summer. Flowers are also showy in the fall as they fade to tan and persist into the winter. The smooth hydrangea is tolerant of many soil types but prefers moist, well-drained, fertile soil.
• Annabelle Extremely large white flowers (almost 1
foot in diameter) are so heavy they
weigh the stems down causing it to
weep.

The panicle hydrangea (Hydrangea paniculata) blooms later than the smooth hydrangea, often not starting until late June. This cone shaped, creamy white flowers are persistent bloomers. As the flowers age, they often become a mottled pink. They often reach 10 feet or more in height.
• Limelight Flowers open a lime green.
• Pee Gee Cone shaped, white flowers. Does well in
full sun.
• Tardiva Large showy white clusters on strong
upright stems.
• White Moth Large irregular spheres in July turning
green in fall.

One of the most popular hydrangea species is the Oakleaf hydrangea (Hydrangea quercifolia). The coarse leaves are 3 to 8 inches long and shaped like oak leaves, hence the common name. The foliage is also noted for its attractive, red-burgundy fall color. This 3 to 5 foot shrub has showy cone shaped, creamy white flowers in June and July. Like panicle hydrangea, the flowers often develop pinkish undertones as they mature. It prefers partial shade in fertile, moist, well drained soil with winter protection.
• Oakleaf Large, coarse textured oak leaf foliage
with large white flowers in June.
• Snow Queen Improved selection with large, pure white
panicles.
• Sikes Dwarf Low growing dwarf form.

Not all hydrangeas are shrubs. (Hydrangea anomala ssp. petiolaris) is actually a climbing hydrangea. It easily clings to tree bark or other structures, often attaining heights over 50 feet. The white flowers are approximately 6 to 10 inches in diameter. Blooming in early July and last for several weeks. The glossy dark green leaves provide the perfect backdrop to show off the blossoms. Another interesting feature of this plant is its exfoliating brown bark. The shaggy bark adds a great deal of interest in the winter making this a multi-season ornamental plant. As with most hydrangeas, climbing hydrangea prefers partial shade to full sun with a moist, fertile, well-drained soil. Give this plant plenty of room to grow.

Another added bonus to most hydrangea flowers is that they make excellent cut and dried flowers. You can bring the blossoms inside to brighten the indoor landscape.

THE SINGLE MOST OFTEN ASKED QUESTION ABOUT HYDRANGEAS

Why is my blue hydrangea pink?

THE ANSWER

Flowers of some cultivars are strongly affected by the pH of the soil in which they are grown. The color changes depend on the concentration of aluminum ions in the soil. This depends in turn on the acidity of the soil, being highest on very acid soils and lowest where the soil is alkaline. The color range depends on the cultivar but the bluest shades are always produced on the most acid soils. A pH range of 5.0 to 5.5 is listed as satisfactory for inducing blue coloration while pH of 6.0 to 6.5 and higher is best for pink coloration.

Aluminum must be absorbed by the plant in order to maintain blue flowers. There is usually aluminum present in the soil, but it is not readily available to the plant. This can only happen in acid soil. In alkaline soil, aluminum forms an insoluble compound which the plant cannot absorb.

To intensify the blue color add 0.25-0.5 oz. of aluminum sulphate per gallon of water and apply periodically through the growing season. A fertilizer low in phosphorous is also highly recommended.

Additional information: Improving the soil

Planting instructions