A snowball hydrangea is another name for a mophead hydrangea, or Hydrangea macrophylla. It is a cultivar of Bigleaf hydrangea, and it's a popular choice for home gardens, especially in the southern United States. Snowball hydrangeas have large, circular flowers, as the name would suggest. However, contrary to the name, the blooms do not have to be white. As with other hydrangeas, the bloom color can change based on the acidity of the soil.
The large flowers on snowball and other Bigleaf hydrangeas are composed of many smaller flower clusters. The plants, which are actually a shrub, bloom in the summer and fall. Blooms can be white, pink or blue. Pink and blue blooms can be created by amending the pH of the soil. In acidic soil, flowers are blue. With more basic soils, the flowers are pink.
When planting any Bigleaf hydrangea, including snowball hydrangeas, choose a site with well-draining soil. The plants will do best in a sunny location that gets some afternoon shade to allow the plant a break from the intense midday heat of the summer. A good location is on the north side of a house or other building.
Snowball hydrangeas should be planted in either the fall or early spring. To plant, dig a large hole as deep as the root ball but about 2 feet wider than the roots. Place the plant in the hole and allow the roots to spread out naturally. When refilling the hole with soil, pack it down firmly to remove any air pockets. Water it immediately after planting.
Snowball hydrangeas need regular waterings to prevent the flowers from wilting in the heat. Each plant should get about 1 inch of water per week. If you want to fertilize your plants, use a 10-10-10, 16-4-8 or12-4-8 fertilizer and apply it up to three times during the growing season, starting in about March, when the weather starts to warm up. Snowball hydrangeas and other Bigleaf varieties should be pruned immediately flowering. Prune away all the dead wood and cut back about one-third of the remaining stems.
Changing Bloom Color
Many growers of snowball hydrangeas like to tinker with the soil pH to change the color of the blooms. The aluminum content of the soil creates the acidity that determines the flower color. In most cases, soil contains enough aluminum to make a slightly acidic soil, which produces blue flowers. If you have a slightly acidic soil but would like pink blooms, you can make the soil more alkaline by adding lime to the soil. If your plant produces pink flowers, you can add sulfur to the soil to create a more acidic soil.