One of the most noticeable plants in our landscapes in late spring and summer are the hydrangeas which are commonly referred to as Bigleaf Hydrangeas (Hydrangea macrophylla). They form either balls of flowers or flat clusters of flowers. Their blooms cannot be missed because many are large and have fantastic purple to blue to pink colors.
There are numerous cultivars available in nurseries. Perhaps one of the most common cultivars is called ‘Nikko Blue’. Another cultivar commonly sold is ‘Dooley’. This selection produces flowers on lateral buds, hence covering the entire plant with flowers. This selection was discovered in Vince Dooley’s yard. For you non-football fans, coach Dooley was the Georgia Bulldogs football coach for 25 years.
There has been a resurgence of hydrangeas in recent years mainly due to new varieties that produce blooms on new growth which allow them to have blooms throughout the growing season. These types of hydrangeas are referred to as “everblooming”
The most popular everblooming hydrangea currently sold is sold under the trade name of “Endless Summer”. Plantings from Quincy, Fla., have bloomed for 33 weeks. This plant has been widely promoted and as you may have guessed, is more expensive than some older cultivars.
Other everblooming hydrangeas that you may encounter are David Ramsey, Decatur Blue, Mini Penny, Oak Hill and Penny Mac. In Quincy, Fla., tests these usually bloom 20 weeks out of the year.
Hydranges prefer a moist area with a lot of organic matter and generous amounts of shade. They can tolerate full sun, but look and perform better with shade. They will wilt in the heat of full sun and must be watered more frequently.
If you question if your soil is right for hydrangeas you may want to amend it. Add 50 pounds of organic matter in a 10 square foot area where you are going to plant your hydrangea. It is a good idea to put four inches of mulch around the base of the plants.
Hydrangeas have many different shades ranging from blue to purple to bright pink These plants add a lot of color to the landscape. The blooms can last for a month on older cultivars. One thing to consider before buying hydrangeas is that the deer love them too!
One interesting thing about these hydrangeas is that flower color can be changed from as soil pH is raised. A pH of 5.0-5.5 is best for deep blue flowers. A pH of 5.6-5.9 usually gives a color in between pink and blue. The flowers turn pink when the pH is 6.0-6.5.
The actual change in color is caused by aluminum. If aluminum is in the plant the color will be blue. If aluminum is absent then the color will be pink. When the soil is acidic, the aluminum is more available to the plant roots. Most soils in southern Georgia are naturally acidic so most bigleaf hydrangeas are blue.
A soil drench of aluminum sulfate will change the flower color from pink or light blue to darker shades of color. Dissolve one tablespoon of aluminum sulfate in a gallon of water and drench the soil around the plant. Do this in March, April, and May.
To make the Hydrangeas turn pink, dissolve one tablespoon of hydrated lime in a gallon of water and drench around the plant in March, April, and May. Avoid getting these drench solutions on the leaves because they may burn the leaves.
Bigleaf hydrangeas grow fast and respond well to fertilization. Use about 2 cups of 10-10-10 per 100 square foot area in March, May, and July. If you just recently planted your Hydrangea, wait one to two months for it to become established before you fertilize. Bigleaf Hydrangeas should be pruned when the flowers begin to fade. Flower buds begin to form in late summer so do not prune after Aug. 1.
Jake Price
UGA Extension Agent/Coordinator, Lowndes County
2102 East Hill Avenue
Valdosta, GA 31601
229-333-5185
jprice@uga.edu