Can You Plant Hydrangeas in Clay Soil?

Clay Soil Description

• Soils are classified by texture into clay, sand, loam or silt. Clay soil is easy to identify -- when it’s wet, it’s sticky, and when it’s dry, it’s hard. Clay soil is composed of tiny particles which bind tightly together when wet. It also has the highest nutrient content of the four classes. The biggest problem with clay soil, however, is that it grabs water and holds it instead of draining freely like sandy soil. For some plants, this situation is deadly. With the proper care, however, hydrangeas do well in clay soil.

Planting Tips

• If you decide to amend the clay soil before planting the hydrangea, plan on doing so over the winter. Spread 8 to 10 inches of wood chips over the soil in fall and allow them to remain through winter. In spring, incorporate the remaining chips into the top 18 to 24 inches of soil. You’ll need to dig a wide hole for the hydrangea, at least five times as wide as its root ball. This loosens the soil in the surrounding area so that the plant’s roots can more easily penetrate the soil as they grow. After digging the hole, use a garden fork or pitchfork to scrape the sides and bottom of the hole to loosen it even more.

Watering the Hydrangea

• The most important consideration when growing hydrangeas in clay soil is to avoid overwatering them, which may cause root rot, a fungal disease caused by various species in the Phytophora genus. Symptoms of root rot include wilting, which may cause confusion because wilting is also the hydrangea’s way of telling you it needs water. However, the wilting that accompanies root rot may be more prevalent at the top of the hydrangea. To avoid the disease, water the plant only when the soil is almost completely dry or if it exhibits overall wilting.

Clay Soil and Flower Color

• Many bigleaf hydrangea (Hydrangea macrophylla) growers enjoy tinkering with flower color by making the soil more or less acidic. When planted in alkaline soils, bigleaf hydrangeas produce pink flowers. Since clay soil is typically alkaline, you can almost count on your hydrangea producing pink blooms. To change them to blue is more of a challenge in clay soil, but it can be done. Add 2 pounds of ground elemental sulfur per 100 square feet of root zone as soon as you see buds in spring. You’ll need to repeat the process every season.