Hydrangea plants can benefit from well-balanced, slow-release organic fertilizer. Some of the best fertilizers for hydrangeas are Espoma Holly-Tone, Dr. Earth Premium Gold, and Happy Frog Fruit & Flower. Hydrangea plants are typically fertilized in early spring and sometimes again in early summer. A good organic mulch can also provide light feeding.
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Hydrangea fertilizer basics
Hydrangea fertilizers are nutrient-rich products designed to boost the health of your plants. Most high-quality fertilizers for Hydrangeas contain the main macronutrients (nitrogen, phosphorus, and potassium) and important nutrients like calcium, magnesium, and trace amounts of important micronutrients. Some products are specifically formulated for flowering shrubs like hydrangeas, but there are also some great all-purpose options that work effectively for hydrangeas.
Hydrangeas are most commonly fed early in the growing season as the soil warms up in the springtime. Mild temperatures and spring rains bring soil nutrients into solution, making them available to plant roots. There is also less competition from other plants and organisms for nutrients early in the growing season.
The best fertilizers for hydrangeas
Hydrangeas can generally benefit from well-balanced, slow-release organic fertilizers. Here are some excellent fertilizer choices for hydrangea shrubs:
- Espoma Holly-Tone Organic Food For Evergreen & Flowering Shrubs (4-3-4)
- Espoma Plant-Tone Organic All Purpose Plant Food (5-3-3)
- Dr. Earth Premium Gold Organic-7 All-Purpose Balanced Organic Granular Fertilizer (4-4-4)
- FoxFarm Happy Frog Fruit & Flower Dry Organic Fertilizer (4-9-3)
- Natural Guard Organic Rose & Flower Food (3-4-3)
- Dave Thompson’s Organic Healthy Grow All-Purpose Plant Food
Remember to follow the instructions for your specific product, as application amounts vary.
How to fertilize hydrangeas
Hydrangea fertilizers are typically offered in three application formats: liquid, granular, or spikes. The application method depends on the fertilizer you choose for your Hydrangeas. Fertilizer is most often applied around the drip line of the branches of the plant.
Liquid fertilizers are concentrates that must be diluted with water as per instructions before being sprayed or poured on the soil. Many products have included scoops, making it easy to measure out 1-2 scoops per gallon of water (or whatever is specified).
Liquid concentrates and water-soluble powdered fertilizers are typically fast-release fertilizers, as the nutrients are already in solution. While many liquid fertilizers are made from synthetic chemicals, more options for liquid organic fertilizers made of natural ingredients are becoming available (like Dr. Earth Flower Girl or Miracle-Gro Performance Organics).
Slow-release formulas are generally applied as a dry product. Granular fertilizers are generally sprinkled atop the soil at a given rate. Watering after fertilizing can start the process of slowly releasing the nutrients into a solution for the plants. Many of the recommended fertilizers in the section above are granular slow-release fertilizers that work well for Hydrangeas (and are also easy to apply).
Spikes are simply inserted into the soil near the base of the plant. A popular brand of fertilizer spikes is Jobe’s Organics All-Purpose Fertilizer Spikes.
Changing hydrangea color with fertilizer
Certain varieties of Hydrangea can change color, with blossoms that can appear pink or blue (see this color chart for hydrangea flowers). These varieties are typically cultivars of Hydrangea macrophylla (Mophead Hydrangea), such as Summer Crush Hydrangea, Bloomstruck Hydrangea, and Nikko Blue Hydrangea. Acidic soils tend to turn these Hydrangeas blue, while alkaline soils tend to turn the flowers pink. Other types of Hydrangeas do not change color with changing soil pH.
Soil acidifiers can be used to turn hydrangea flowers blue. Acidifiers like sulfur and gypsum lower the pH of soils to produce blue blooms (elemental sulfur and gypsum are often considered safer for the environment and for humans than aluminum sulfate). Soil Acidifiers are typically applied every few months until the desired soil pH (4.5-5.0 for blue) is reached. Some hydrangea fertilizers (like Espoma Holly-Tone) contain acidifiers like sulfur to support acid-loving plants (making them ideal for varieties with blue flowers).
Garden Lime can be used to turn hydrangea flowers pink. Alkaline soil amendments like dolomite lime raise the pH of acidic soils to bring them to a more neutral level. Garden lime is typically applied in early spring and/or early fall until the desired neutral pH (5.5-6.5 for purple, 7.0 for pink) is reached. For pink flowers, use all-purpose garden fertilizers (like Espoma Plant-Tone) rather than those formulated specifically for acid-loving plants (like products for rhododendrons, azaleas, and blueberries).
When to fertilize hydrangeas
The best time to feed hydrangea shrubs is in early spring. As the plants come out of dormancy, they grow new root systems and take up high levels of nutrients to prepare for the upcoming seasons. Early in the growing season is also a great time to feed hydrangeas because there is generally some rainfall, and the weather is not yet too hot. Plant roots absorb nutrients that are in solution with water, so the presence of nutrient-rich water is key for absorption. Early spring is also a great time to apply organic mulch.
If a garden soil test shows that your soil is low in nutrients, hydrangea plants can be fed again in late spring or early summer. There are also certain types of hydrangeas that are “heavy feeders” – namely cultivars of Hydrangea macrophylla (Bigleaf Hydrangea). These Hydrangeas set their flower buds in the fall and also tend to have more foliage and larger blooms (necessitating extra nutrition).
The timing depends on the instructions for the specific fertilizer you’re using. For instance, a 90-day slow-release fertilizer could be applied in March and again in June. A 60-day slow-release product could be applied in March, May, and July.
Fertilizing hydrangeas is generally avoided in late summer and early fall. In most climates, this means skipping fertilizer in August-October. Plants that are in need of added nutrients can be fed again in late fall, provided the soil isn’t frozen.
“Nutrient availability from soils tends to be greatest early in the growing season when (1) warming of soils or the coming of rains brings a flush of nutrients into the rhizosphere, (2) microbes that compete with roots for soil nutrients are just beginning to recover from the dormancy of winter or the dry season, and (3) new plant roots explore virgin soil. Plants obtain a substantial portion of their mineral nutrients during this time.”
Mineral Nutrition of Plants: Principles and Perspectives, by Emanuel Epstein and Arnold J. Bloom
Fertilizing hydrangeas during planting
Some gardeners like to use specialty transplanting fertilizer when planting new hydrangeas in the garden. Popular transplanting fertilizers include Espoma Bio-Tone Planting Food, Natural Guard New Plant Starter Food, and Dr. Earth Root Zone Premium Starter Fertilizer. While these are not strictly necessary in most cases, they can help provide a nutrient-rich environment for the plant to become established. Just be sure to follow the instructions on the package.
How often to fertilize hydrangeas
Hydrangeas are generally fertilized once or twice per year, but feeding frequency can vary. Hydrangeas planted in rich soil may not require commercial fertilizer, while plants in nutrient-poor soil may benefit from feeding three times per year.
Start with a soil test to determine which nutrients are deficient. Then choose a fertilizer product that contains adequate amounts of the nutrients your soil is deficient in. Read the instructions on the specific fertilizer you’ve chosen and follow the frequency instructions listed on the package. Generally, the hydrangea plants can be fed 2-3 times per year. Avoid feeding hydrangeas in late summer to early fall or when the ground is frozen.
Follow up with subsequent soil tests to see how the nutrient levels are improving. Always include an organic mulch over the soil surface, like homemade compost.
Certain types of Hydrangeas are more hungry for nutrients than others. Panicle hydrangeas and other cold-hardy types are generally happy with one feeding annually, but the heavy-feeding mophead hydrangeas may need 2-3 feeds per year.
“Plants on poorer soils should be mulched and also given a balanced feed a couple of times a year, when in growth. The additional nitrogen will help the stems and leaves grow fast and strong, but avoid feeding in late summer and autumn as new shoots produced after that point will be more susceptible to frost damage.”
Hydrangeas: Beautiful Varieties for Home and Garden, by Naomi Slade
How to tell if hydrangeas need fertilizer
The most scientific way to tell if hydrangeas need fertilizer is to get a proper laboratory soil test. This will tell you which nutrients (if any) are lacking in the soil within the root zone of the plant. Soil tests often give specific recommendations for a fertilizer routine, making it easy to correct any problems.
Another way to investigate whether or not hydrangeas need fertilizer is to address any other common problems. Ensure the plant is getting enough sun (or enough afternoon shade) to thrive. Different types of hydrangeas have different needs in terms of sunlight. Also, take care to keep the soil moist and observe and check if it is draining excess water away. The soil should be moist, but not soggy – rather like a wrung-out sponge. See if the plant improves after a few months with this extra attention.
How to make natural fertilizer for hydrangeas
It’s easy to make natural fertilizer for Hydrangeas at home. The easiest way to make Hydrangea fertilizer is to make leaf mold. Gather up your autumn leaves, shred them if you have time, and perhaps add some coffee grounds for a bit of nitrogen. Then just let them compost into a fine, dark, natural plant food that’s full of balanced nutrients for your hydrangeas.
“If you have “perfect” rich, moist, free-draining soil, you may very well get away with applying a good mulch around the roots of the plant in late autumn or winter – something like spent compost or well-rotted manure, spread around the base of the plant, but not touching the stem, is ideal.”
Hydrangeas: Beautiful Varieties for Home and Garden, by Naomi Slade
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