How to Grow Hydrangea

Hydrangeas prefer morning sun and afternoon shade. Grow as a single plant or several for greater impact. They like rich, organic, well-drained soil. This plant can be grown in containers and adds striking interest to patios. If growing in a container, use a good quality potting mix. Avoid filling containers with soil from garden beds as it can be too heavy and not drain properly. Look for compact cultivars.

Avoid sites that are hot and dry.

Some hydrangeas will have blooms that are either pink or blue, depending on the pH of the soil. If the soil is acidic with a pH of lower than 6, the blooms will be blue. If the pH is 6 or higher, which is alkaline, the blooms will be pink. Other hydrangeas have colors that are based on the genetics of the plant and you cannot change the color of the bloom by changing the pH of the soil.

Keep track of which kind of hydrangea you are growing as that is crucial when it comes to pruning the plant. Hydrangeas typically grow 4- to 12-feet, depending on the variety. They are fast growers.

The best time to plant is in the fall or early spring. Rather than simply digging a hole to plant your hydrangea in, prepare the soil in a larger area such as a planting bed or an area at least two-feet-wide and one-foot deep. Add plenty of composted organic matter and work it into the top 8- to 12-inches of soil.

Make sure the top of the root ball is level with the soil surface. Water thoroughly after planting. Add organic mulch such as pine straw or pine bark around the plant to help keep moisture levels even and to prevent weeds. Water thoroughly after planting.

Hydrangeas like water. Keep the soil evenly moist, but not soggy, throughout the growing season, particularly in the spring when flowers are forming and during the hot summer temperatures when the plant is in bloom.

When to prune is one of the most asked questions about this plant. Some bloom on old wood (previous season’s growth), some bloom on new growth (current season’s growth), and some of the newer cultivars are repeat bloomers and bloom on both old and new growth, making pruning less of an issue. It is important to know which type of hydrangea you have because that is crucial information when it comes to the best time to prune your plant. If you prune at the wrong time you may be reducing or eliminating blooms.

If you are unsure which plant you have, wait until after blooms fade and remove them but avoid pruning after August 1. Bigleaf hydrangeas form flower buds in late summer for the following year. If after August 1, wait until early spring when new growth emerges. Remove any dead stems but leave live stems which likely will have flower buds.

Fertilizing

An application of an organic fertilizer or an all-purpose 10-10-10 fertilizer may be beneficial during the growing season. Both can be found at your local garden center. Follow label directions. Water after fertilizing.

• Wait four to eight weeks after planting to fertilize.
• A soil test will provide information on your pH levels. See FAQs for detail on how to change pH for pink or blue blooms for bigleaf hydrangeas.

Controlling Pests, Diseases, and Other Problems

Hydrangeas have few serious problems with insects, pests, and diseases. If leaf diseases show up, it may be Cercospora leaf spot, anthracnose, Botrytis blight, or powdery mildew. Remove and dispose of infected leaves on the plant and on the ground. 

• Water the plant at the base of the plant rather than from the top. Water early in the day to allow the foliage to dry before nightfall. If foliar problems persist, fungicidal sprays may be used. Follow label directions.
• Insect pests include aphids, leaftiers, spider mites, and rose chafers. If needed, use insecticidal soap or horticultural oil. 
• Japanese beetles seem to like oakleaf hydrangeas. Pick or knock them off into a container of soapy water.

• Paying attention to your planting site and adding plenty of organic material and working it into your soil before adding your hydrangea is the best way to give your plant a good, healthy start.
• Keep track of the hydrandea type you have in your garden, and prune accordingly to maximize bloom production. If you’re unsure, don’t make drastic cuts unless you are willing to risk a season without blooms.
• Make sure your plants are in soil that drains well. Even though they like water, hydrangeas don’t do well in soil that is poorly drained. It also can cause root rot.