It's hard to beat hydrangeas for flower power in the summer landscape. That said, to get the most out of your hydrangeas will require proper fertilization and watering. Fertilize too much and you'll get more foliage and diminished bloom. By adjusting soil pH you can change the colors of some types of hydrangeas. Read on to find information and tips for how to fertilize hydrangeas.



Fertilizing Hydrangeas

Scroll down for how to change hydrangea flower color


All species of Hydrangea will benefit from fertilization. One of the most important things to know is to avoid over-feeding your hydrangeas. Fertilize too much and you'll get more foliage and diminished bloom. Also avoid the use of quick-release fertilizers that are high in nitrogen, the first of the three numbers on a package of fertilizer. Too much nitrogen also causes excessive foliage growth and diminished bloom.


Feeding At Planting Time

If you use organic matter as a soil amendment at planting time there is usually no need to apply fertilizer. That said, you can always apply a slow-release shrub & tree food or organic plant food as directed on the product label.

After planting, spread fertilizer at recommended rates on top of and around the rootball. Fertilizer can be worked into the top inch or two of the soil. Additionally, a one- or two-inch layer of compost or cured wood or bark mulch or chips, or pine straw, can be applied to help conserve moisture and suppress weed growth. Avoid using fresh chipped wood for mulch until it has cured in a pile for at least 6 months, a year is better. Avoid placing or piling mulch directly against the base of your plant as this could cause the bark to rot.

Tip:  For an extra boost you can water your newly planted hydrangeas with a solution of Root Stimulator, which contains B vitamin and other nutrients that stimulate early root formation and stronger root development, reducing plant shock and promoting greener, more vigorous plants.


Thereafter

Fertilize your Hydrangeas annually in late winter or very early spring with a slow-release shrub & tree food. Alternatively, you can feed with a natural organic plant food

In warmer regions, feed hydrangeas a second time in June. 

In all regions, warm and cold, cease fertilization of hydrangeas two months before the average first-frost date in your area. Late fertilization of hydrangeas produces lots of lush, tender growth at a time when plants should be preparing for winter dormancy. Too, the tender new leaves allow the cold to enter the branches through the foliage, which can cause damage to the plant. 


Feeding Hydrangeas In Containers

Feed Hydrangeas growing in containers as directed with a slow-release granular or water soluble fertilizer designed for use in containers. 



Changing Hydrangea Flower Color


Hydrangeas are happy growing in moderately acid to moderately alkaline soils ranging between 5.0 to 8.0 on the pH scale. This is great for two reasons. One, because hydrangeas perform well in such a wide range of pH, it means there's usually not a need to adjust soil pH to make them happy. Two, because it allows you a wide range for adjusting soil pH, which can change the flower colors on the specific Hydrangea species.

Though the color of white-flowering hydrangeas cannot be changed. The flower color can be changed on most Hydrangrea macrophylla, commonly called big leaf, mophead, or French hydrangeas, Hydrangea macrophylla normalis, commonly called lacecap hydrangeas, and Hydrangea serrata, which are similar to the mopheads but with smaller leaves and flowers that resemble lacecaps.

The pH of the soil in your landscape or garden will ultimately determine the flower color of your hydrangeas, at least those that can change color. For example, you could purchase and plant a mophead hydrangea with blue flowers on it this year. Then, next year, the same plant produces pink flowers. This would indicate alkaline soil conditions. 

In strongly acid soil (pH below 6) hydrangea flowers turn blue. In alkaline soil (pH above 7) flowers turn pink or even red. In slightly acid or neutral soil (pH 6 to 7), blooms may be purple or a mix of blue and pink on a the same shrub. Keep in mind that some Hydrangea varieties vary in their sensitivity to pH.

So, to change the flower color of your Hydrangea, you'll have to adjust the pH of the soil. This is done with the application of specific soil additives. 


From Pink to Blue or PurpleSoil additives, such as soil sulfur or aluminum sulfate, lower soil pH, making it more acidic, which changes pink flowers to blue and purple shades. Follow instructions on product label for application rates.

From Blue or Purple to Pink - To change flower color from blue or purple to pink, apply a fast-acting pelletized lime.


Tip:  Adding organic compost to the soil, or using it regularly as mulch, can help to increase soil acidity and maintain acid soil conditions. 

Note:  Keep in mind that the color changing process can take two or more growing seasons to accomplish. Adjusting acid soil to alkaline doesn't seem to take as long as from alkaline to acid. 




How To Water Hydrangeas


Hydrangeas perform best in a moist but well-drained soil. When established they are somewhat tolerant of dry periods.  As with so many other ornamental shrubs, hydrangeas don't like a constantly soggy or wet soil, which can lead to root rot and other harmful plant diseases. 


At Planting Time

Immediately after planting your Hydrangea deep soak the soil in the planting area, including the rootball, to a depth equal to the height of the rootball. For an extra boost you can water your newly planted hydrangeas with a solution of Root Stimulator, which contains B vitamin and other nutrients that stimulate early root formation and stronger root development, reducing plant shock and promoting greener, more vigorous plants.


During the First Growing Season

In average garden soil you should not have to water your newly planted Hydrangea every day. More often than not, this causes soggy soil conditions that can lead to root rot and other plant diseases. In the absence of sufficient rainfall, water only as needed to keep the rootball and surrounding soil damp to moist. Keep in mind that deep soaking less frequently is much better than splashing just a little water on the plants every day. Shrubs planted during the winter dormant season, when plants are not actively growing and evaporation is much slower, will require much less water. So, be extra careful not to overwater during winter!


Thereafter

When established, hydrangeas are somewhat drought tolerant. That said, during prolonged periods of drought, especially during summer, plants may require supplemental water. Wilting new leaves, or new stems that are bending over, are indicators that your plants could use a good deep soaking.


TIP:  When watering with an automated irrigation system it's best to set your timer to water during the early morning hours, and not in the late evening or at night, which can lead to the onset of fungus and other foliar diseases. During the first few weeks after planting, check soil moisture often and adjust irrigation time if necessary to keep the soil moist, not wet.



Related Articles from Our Experts



Plant Long & Prosper!

Questions? Contact Us!