Few summer-blooming shrubs are as iconic as hydrangeas, which boast gorgeous, bouncy blooms that add texture and color to any garden. While these shrubs are low-maintenance, incorporating fertilizer into your care routine can improve plant health and spur new growth, resulting in a profusion of bold blooms. 

While fertilizer can transform your hydrangeas, doing so the wrong way and at the wrong time of year may encourage growth that doesn’t survive the winter, while over-fertilizing can result in plant burn or excess foliage. What’s more, some hydrangeas can change color based on the soil’s pH level, meaning fertilizer can change the hue of your plant. 

Perfect your fertilizing process with these simple, expert-approved tips and make your hydrangeas the showiest on the block.

When to Fertilize Hydranges

The best time of year to fertilize hydrangeas is at the start of their growth cycle in early spring, as the plants begin to push out new growth. “This gives them the boost they need to produce healthy vegetation,” says Linda Vater, plant expert for Southern Living Plant Collection. If you’re caring for re-blooming varieties like Endless Summer, a second application in early summer can help support flowering, she adds.

Best Fertilizer to Use for Hydrangeas

Since hydrangeas are susceptible to over-fertilizing, opt for a balanced fertilizer that reduces the risk of accidentally damaging your plant. “A slow-released, balanced (10-10-10) fertilizer will release the necessary nutrients over time, including N-P-K (nitrogen, phosphorus, and potassium),” says Vater.

That said, many hydrangeas can thrive without commercial fertilizers. “In most parts of the country where there is good fertility in the soil, hydrangeas don’t need to be fertilized,” says Andrew Bunting, vice president of horticulture at the Pennsylvania Horticultural Society,

Instead, boost the plant’s bloom factor with organic compost, which is better for the soil, your plants, and local wildlife. “Mulching around the base of hydrangeas with an organic-rich compost will build fertility in the soil and therefore contribute to the vigor of hydrangeas and other plants,” he says.

How to Fertilize Hydrangeas

Plan to fertilize your hydrangeas in the morning. “The morning is ideal because the soil is still cool, and the plant has the entire day to absorb the nutrients, minimizing the risk of fertilizer burn,” says Vater.

Water the plant before fertilizing, and apply the amount of fertilizer indicated on the packaging (exact quantities will vary based on the size of your garden and the specific hydrangea). After applying the fertilizer, thoroughly water the plant again. “This helps distribute the fertilizer evenly and prevents fertilizer burn,” says Vater. 

Stop applying fertilizer by midsummer (late July or early August) to prepare your plants for winter. “Fertilizing too late can stimulate new growth that will be vulnerable to frost,” Vater says. 

How to Fertilize Container-Grown Hydrangeas

Container-grown hydrangeas are often fertilized with a diluted liquid fertilizer, says Vater. Follow the same process, but consider applying fertilizer more often. “Hydrangeas grown in containers may require more frequent fertilization, as nutrients will leach out of the soil with watering,” says Vater.

How to Fertilize Hydrangeas to Change Bloom Color

Certain hydrangea varieties, including Hydrangea macrophylla and Hydrangea serrata—can bloom in different hues depending on the soil’s pH. “The general rule of thumb is that hydrangeas with a pH below seven will be blue, and above seven, they will turn pink,” says Bunting.

Test the soil to identify its current pH, then use amendments or fertilizer to lower or raise the acidity of your soil. “To turn hydrangea blooms blue, lower the soil pH with a specialty fertilizer or aluminum sulfate. To turn hydrangea blooms pink, raise the soil pH with a specialty fertilizer or garden lime,” says Vater, adding that the best time to apply soil amendments to change bloom color is in fall or early spring.

As with all gardening efforts, the key is patience. “Remember that these color changes will occur over time, not immediately,” says Vater. “It may take several weeks or even months to see noticeable color changes.”

Common Mistakes to Avoid When Fertilizing Hydrangeas

If you choose to fertilize your hydrangeas, these common mistakes can cause more harm than good. Keep your plants blooming by avoiding these pitfalls.

Over Fertilizing

Using too much fertilizer can result in plant burn or encourage your hydrangeas to sprout extra leaves and fewer blooms, says Vater. Following the instructions on your product for quantity and frequency will yield the best results.

Using the Wrong Fertilizer

The commercial fertilizer you choose should always be balanced and designed for use with flowering plants, says Vater. This prevents your hydrangeas from receiving too much or too little of a specific nutrient.

Using Peat Moss as Fertilizer

Though Bunting encourages organic alternatives to synthetic fertilizers, he recommends avoiding peat moss. “Peat moss is promoted as an organic approach to bringing acidity to the soil, but the harvesting of peat moss comes from pristine ecosystems in Canada and is not environmentally sustainable,” he says.

Incorrect Application

Avoid fertilizing when the plant is stressed or during extreme heat or drought, says Vater. And watch where the fertilizer lands: “Apply it to the soil around the plant’s drip line, and not directly on the foliage,” she says.