A perennial favorite in the landscape, hydrangea is hardy in a wide range of growing zones and is a relatively easy keeper. While hydrangeas vary in form, color, and bloom time, they are known for the large flower heads that cover the plants—so large, in fact, the blooms often weigh down the stems. Once established, the hydrangea is one of the summer season’s most impressive shrubs, but it needs fertilizer to reach its full potential.
The best fertilizer for hydrangeas should contain a blend of nutrients to encourage healthy root and branch development while boosting the color, size, and quantity of flower heads. Don’t just grab a package of garden fertilizer off the shelf, though. Instead, read on to learn what to look for when choosing a fertilizer for hydrangeas, and find out why the following products can help this impressive plant become a focal point in the landscape.
- BEST OVERALL: Scotts Company Miracle-Gro Acid-Loving Plant Food
- RUNNER UP: BIOADVANCED All in 1 Rose Care
- BEST BANG FOR THE BUCK: Miracle-Gro Water Soluble Bloom Booster Flower Food
- BEST FOR BLOOMS: JR Peters Jacks Classic Blossom Booster Fertilizer
- BEST ORGANIC: Dr. Earth 703P Organic Acid Fertilizer
- BEST FOR BLUE: Espoma GSUL6 Soil Acidifier, 6-Pound
What to Consider When Choosing the Best Fertilizer for Hydrangeas
Like all plants, hydrangeas draw nutrients from water, sunlight, air, and soil, but not all soil contains the nutrients necessary for robust growth and flower development. That’s where hydrangea fertilizer can help. The best fertilizer for any individual hydrangea plant will depend on the gardener’s preferred method of delivering the fertilizer to the soil, and the condition of the existing soil.
Hydrangea fertilizers come in three primary forms: liquid, granule, and compressed spikes. All three offer slightly different benefits.
- Liquid: Available as either a concentrate for diluting with water or a ready-to-use product, liquid fertilizers are quickly absorbed by the plant’s roots and leaves for a fast boost of nutrients. Depending on the product, liquid fertilizers are either sprayed on the plant’s foliage or poured around the plant’s base.
- Granules: One of the most common forms of fertilizers, granule fertilizers can either be dissolved in water and poured on the soil or sprinkled around the plant’s base. Time-release granules, which have a polymer coating, should be worked into the soil around the hydrangeas’ base with gardening tools. They dissolve slowly and offer the plant a long-term supply of nutrients.
- Spike: Like time-release granules, gardeners often use spikes if they’re looking for a long-term plant food. This fertilizer is compressed and shaped into hardened spikes that the gardener pushes into the soil around the plant’s base. Over the course of 2 or 3 months, the spikes slowly dissolve and provide nutrients for the plants.
Organic vs. Inorganic Fertilizers
Most fertilizers designed for feeding hydrangeas contain chemicals, but a few feature natural ingredients. Both are suitable for boosting the plant’s health and producing large, beautiful blooms. The choice of one type over the other is a matter of personal preference.
- Inorganic: This type of fertilizer contains chemical and synthetic nutrients. It has been formulated in a laboratory to produce specific growing results, such as larger or more abundant blooms or an increased acidity level, which is desirable when growing hydrangeas. Inorganic fertilizers may also include time-released ingredients that dissolve slowly and feed the plant over a period of weeks or months.
- Organic: Some gardeners prefer using only natural fertilizers that contain ingredients such as earthworm castings, poultry manure, or compost. Organic fertilizers contain no chemicals, and they may not be as strong as inorganic fertilizers. They may, however, help increase soil health in addition to providing nutritional value. For example, compost doesn’t just provide the plant with nutrients; it also helps heavy clay soil drain better.
Commercial fertilizers are labeled by the amounts of nitrogen (N), phosphorus (P), and potassium (K) they contain by weight, which appears on the package as the N-P-K ratio. Hydrangeas will benefit from an all-purpose, balanced fertilizer, such as a 10-10-10 N-P-K, that contains equal amounts of each nutrient. A balanced fertilizer will encourage healthy foliage as well as bountiful blooms. For gardeners explicitly seeking to increase the blooms’ quantity and size, a fertilizer with a higher concentration of phosphorus (the middle number), such as a 10-20-10 N-P-K, may be beneficial.
The hydrangea will tolerate partial sun, but it prefers a mostly shady spot in the yard. When possible, locate the shrub where it will not receive direct sun in the late afternoon in hot climates. Morning sun is usually acceptable and well tolerated. In northern climes where afternoon temps are moderate, some hydrangeas will also thrive if they receive some early afternoon sun. It’s the combination of hot temperatures and blazing sun that can take a toll on these spectacular shrubs. Hydrangeas like a permanent spot in the landscape, so planting them in pots or grow bags might not allow the shrubs to reach their full potential.
Well-drained soil that’s high in organic matter is optimal for growing hydrangeas. Heavy, clay-type soil and sandy soil will benefit from additional organic matter, such as compost or dried leaves. By adding organic matter, the gardener will increase drainage and enhance the soil’s phosphorus level, which is favorable to producing colorful hydrangea blooms. Before amending soil, it’s a good idea to take a sample of the existing soil to a local extension office for testing. The test results will include recommendations for creating healthy, balanced soil.
Color and pH
White hydrangea species produce only white flower heads, but an interesting thing happens to colored hydrangeas when the gardener alters the soil’s pH level. The more acidic the soil’s pH, the more likely it is that the hydrangea flowers will be blue. The pH scale ranges from 0 to 14, with 7 considered neutral. Levels higher than 7 are considered alkaline, while levels lower than 7 are considered acidic. The greater the pH variation, the more pronounced the hydrangea color change.
- Neutral: At a neutral pH level, around 7, colored hydrangea will produce flowers in shades of pink to deep pink.
- Alkaline: At pH levels higher than 7, hydrangea flowers are a light, clear pink hue.
- Slightly acidic: When the soil’s pH is around 6, the blooms take on a dark pink or even slightly red or purple hue.
- Strongly acidic: When the soil’s pH level is lower than 6, hydrangea blooms tend to turn blue. This is the most desirable color for many gardeners, who regularly amend the soil to achieve beautiful blue flower heads.
When shopping for hydrangea fertilizers, you may notice that a good number of them are called acidic fertilizers. In addition to the product’s N-P-K nutrients, acidic fertilizers contain pH-changing additives, such as sulfur or aluminum sulfate. For those who strive for blue flower heads, it’s worthwhile to purchase a pH soil tester to monitor the soil’s pH level.
Our Top Picks
To qualify as a top pick, a fertilizer should provide the nutrients hydrangeas need for developing strong branches, healthy foliage, and beautiful blooms. The best fertilizer for hydrangeas will vary depending on the gardener’s goals for this spectacular shrub. Any one of the following fertilizers is well suited for use on hydrangeas, but keep in mind that more is not necessarily better when it comes to fertilizing plants. Follow application instructions carefully. Do not overfeed hydrangeas; rather, err on the side of too little rather than too much and use fertilizer in combination with other soil amendments and an optimal growing location.
The best overall pick is an acid-based fertilizer from a well-known and respected manufacturer in the gardening industry. A water-soluble plant food designed for hydrangeas and other plants that prefer slightly acidic soil, this fertilizer comes in a 1-pound box of quick-dissolving granules. It features a 30-10-10 N-P-K ratio to help hydrangeas get off to a robust start in spring and grow vigorously throughout the summer. For best results, dilute the product in water as recommended and apply around the plant’s base every 7 to 14 days. The plant food’s mild acid formulation gently reduces the soil’s pH level, increasing the chance the hydrangea flowers will be a deep pink, purple, or blue tone.
- Instant acid plant food
- Feeds through roots and leaves
- Increases bloom output
- Might need extra applications on alkaline soil
- Smaller box than expected
This flower fertilizer comes in a 32-ounce jug of concentrated liquid and is suitable for use on many types of flowers. A single spring application will provide hydrangeas with a steady 9-14-9 N-P-K diet for up to 6 weeks. Designed to encourage large, bountiful blooms, this fertilizer should be diluted in water and then poured around the base of the plant. In addition to the N-P-K nutrients, the fertilizer contains insect control to protect plants from Japanese beetles and other pests, and it also contains a disease protectant that discourages mildew and fungus.
- Promotes strong plants while fighting pests
- Prevents powdery mildew, block spot, and more
- Lasts for 6 weeks
- Works on more than just roses
- Must be mixed with water
- Includes ingredients that could harm bees
There’s no need to spend a bundle on plant food. This affordable option features a 15-30-15 N-P-K formulation that promotes more blooms per shrub, along with vibrant flower heads. This is an all-purpose blossom booster that’s suitable for use on a wide variety of perennial and annual blooming plants, including hydrangeas. It provides various minerals, including copper, boron, and iron, to supplement common nutrient deficiencies. The water-soluble formulation should be applied every 7 to 10 days throughout the growing season for the biggest, brightest blooms and healthiest plants.
- Promotes more blooms in most flowers
- Mixes easily in watering can
- Improves the size of some plants
- Must be diluted properly and applied regularly
Those who dream of growing hydrangea bushes covered in flower heads should check out this option from JR Peters. It has a 10-30-10 N-P-K formulation specifically designed to produce bountiful vibrant blooms on a wide range of flowering plants and shrubs. This fertilizer is made to dissolve in water, and the solution is then poured around the base of the plant where it is quickly absorbed by the roots. For continuous large blooms, apply the product in mid-spring and then every 7 to 14 days afterward. Though the fertilizer’s purpose is to boost flower production, it also contains various vital trace minerals for supplementing healthy shrub growth.
- Includes trace minerals with fertilizer formula
- Works for starts, transplants, and established plants
- Increases blooms on most plants
- Effectiveness may depend on existing soil conditions
Boost acid-loving hydrangeas with a completely organic product. Dr. Earth’s acid fertilizer contains only natural ingredients, including alfalfa meal, bone meal, and kelp meal, in a 3-4-3 N-P-K formulation. In addition to nutrients, it contains select strains of probiotics that improve soil health and increase plant performance. Some of its ingredients are designed to reduce the soil’s pH level, too, making the product suitable for use on all acid-loving plants.
For the best results, apply in mid-to-early spring and then every 60 days afterward. The granules should be mixed with the soil and watered well.
- Continuously feeds acid-loving plants for months
- Includes probiotics and microbes
- Effective for transplanting or a mid-season boost
- Improves leaf and bloom output
- Strong smell could attract dogs or insects
- Feeds acid plants but doesn’t lower soil acidity
Gardeners and landscapers looking to create highly desirable blue flower heads need look no further than this soil acidifier from Espoma Soil. While not a strict fertilizer in the common sense—Espoma does not come with an N-P-K ratio—the product does contain elemental sulfur and gypsum that act together to lower the soil’s pH level, encouraging blue hydrangea blooms. For the best results, apply Espoma granules around the plant’s base in early spring before flowerhead buds develop and reapply every 60 days.
Espoma’s soil acidifier is an all-natural, organic product. It comes in a 6-pound bag and is suitable for use on hydrangeas and other acid-loving plants. Be aware that pH levels adjust gradually. Depending on the soil’s current pH level, two or more applications may be necessary before the acidity is low enough to produce blue flower heads. This product can be used in conjunction with an all-purpose fertilizer to encourage robust plant health as well as blue flower heads.
- Amends soil for acid-loving plants
- Lasts a long time
- Doesn’t conflict with other fertilizers
- Safe and organic minerals
- Might need to use more than expected
Our top pick is the Scotts Company Miracle-Gro Acid-Loving Plant Food, as it works effectively to improve bloom production for hydrangeas even if the soil conditions aren’t acidic. For the best option to help increase the soil’s acidity, consider Espoma’s soil acidifier.
How We Chose the Best Fertilizers for Hydrangeas
To keep hydrangeas growing and blooming bountifully, you need a fertilizer or soil amender that’s made specifically for these acid-loving plants. Our recommendations include a variety of options to help improve the health and beauty of these plants. We’ve selected traditional water- soluble fertilizers that help stimulate root growth, granular fertilizers with microbes and fish meal, and soil amenders that help increase the soil’s acidity to achieve blue flowers. As a bonus, we also included an all-in-one product that is an effective pesticide and fertilizer that also helps plants resist common diseases.
We’ve included some low-cost options, too; however, they may require frequent application for effective fertilization all season. Our favorite options effectively increase the bloom rate of hydrangeas, and gardeners can choose between organic and non-organic products.
Hydrangeas grow in most regions of the country and are prized for their spectacular blooms, so it’s natural to have a few questions about how to make the most of these eye-catching shrubs.
Q. When do hydrangeas start to bloom?
In warm climates, hydrangeas start to bloom in early summer. In northern climes, they bloom in mid-summer.
Q. What is the best time to fertilize hydrangeas?
It depends on the type of fertilizer. It’s a good idea to give hydrangeas a first feeding in mid-to-late spring. After that, apply additional fertilizer at intervals recommended by the manufacturer. Time-released fertilizers might need to be applied only once every 3 months, while other types should be applied every 1 to 2 weeks.
Q. How do I fertilize hydrangeas?
It’s essential to follow the directions on the product label. Liquids can be diluted and poured around the plant’s base or sprinkled on the foliage, while granules are often worked into the top inch or so of the soil. Fertilizer spikes are inserted near the base of the plant and pushed beneath the soil’s surface.