Bigleaf hydrangea growing tips
The bigleaf hydrangea can be a popular plant in both the florist and landscape areas. The bigleaf hydrangea, Hydrangea macrophylla, is also known by the name French, Japanese or snowball hydrangea. One characteristic that makes bigleaf hydrangea so popular is the ability of the owner to change the color of the bloom by changing the soil pH. You can change the bloom from pink to blue or from blue to pink by working on the soil pH in the growing area. I will be sharing information today from a publication by Dr. Gary Wade, retired UGA Extension Horticulturist.
For starters, I would like to give some background on bigleaf hydrangea cultivars. In actuality, there are more than 500 cultivars of bigleaf hydrangea. These cultivars are divided into two main groups.
There are the hortensias which will have the large snowball-like flower clusters and then the lacecapes which will demonstrate more flat-top flowers which will have more fertile, non-showy flowers in the center and more showing sterile flowers on the outside. I would venture to say that more folks are more accustomed to cultivars with the snowball-like flowers in our area.
The bigleaf hydrangea needs a growing spot that provides moist, but welldraining soil. I will add the area needs to provide morning sun and afternoon shade. Keep in mind to stay away from hot and dry exposed sites for bigleaf hydrangea. Our information states that you can get cold damage to bigleaf hydrangea on the buds in winter or late spring so you must be prepared to protect them.
You can do this by covering the plant with an old sheet, blanket or even a cardboard box when temperatures go below freezing. Our info adds that you can make a chicken wire cylinder and place around the plant and then fill with leaves to provide cold protection too. Another note is that bigleaf hydrangea can be a container plant so if you go that route, you can bring the plant indoors when the night temps are cold.
If you are going to plant in the ground, we suggest you prepare the soil in a wide area. You should apply 50 pounds of composted organic matter per 10 square feet and then incorporate this material into the top 8 to 12 inches of soil. You can do this with either a shovel or a tiller. The organic material added will help in several ways. The organic matter will help with the water holding capacity of the spot and also help hold nutrients. When you plant make sure the top of the root ball is level with the soil surface.
You will want to water completely after you transplant the hydrangea into the spot. You also need to apply 3 to 5 inches of organic mulch such as pine straw, pine park or fallen leaves to the surface to help control weeds and conserve moisture.
Keep in mind to not fertilize until the plant is established. This establishment will normally take 4 to 8 weeks after transplanting. Note that we live in an area will most of our soils are acidic or lower on soil pH so more flowers will be blue. Bigleaf hydrangea will need multiple light applications of fertilizer in the growing season. You can use a general fertilizer such as 8-8-8 or 10-10-10.
The rate will be 1 pound (2 cups) per 100 square feet in the months of March, May and July. You do not have to remove or pull back the mulch when you fertilize. You will though need to water soon after the fertilizer application to dissolve the fertilizer and get the fertilizer to the roots. I will add that the bigleaf hydrangea is called a water demanding plant that works better in a moderate water use landscape zone. You need to water when the plant starts to wilt in the absence of rainfall. Our information states that it is important to avoid stress to the plants especially in the spring when flower formation is taking place.
On flower color, our research shows that the actual issue of color variation in the bloom is based on the presence or lack of aluminum compounds in the flowers. If aluminum is present in the plant, the flower color is blue. If aluminum is in small amounts, the color can be called “in between” and if aluminum is absent, the flower color will be pink. The soil pH will indirectly affect color by affecting the availability of the aluminum in the soil. When pH is 5.5 or lower, aluminum is more available to plant roots. When the soil pH is 7.0 or higher, aluminum available to roots is decreased so the color will be more pink.
To slowly change flower color from
of wettable sulfur per 10 square feet and water in. To make flower color pink, you broadcast one cup of dolomitic lime per 10 square feet and water into soil. It can take approximately a year to see a big change in the color this way.
For quicker flower color change, liquid soil drenches can be used. I will try to share that information in a future article.