Hydrangeas are easy to keep flowers, but they need fertilizer to reach their greatest potential. With their bold, large, green foliage, and oversized, bulbous flowerheads, hydrangeas are a summer favorite all around.
These flower bushes will grow well on their own, but to get thick, healthy, full bushes, and heavy flowers you’ll need the right fertilizer. These huge flower heads are what attract so many gardeners to these plants. You can enjoy the big flower mounds both on the bush and in a vase as a wonderful cut flower arrangement.
You could just grab the first one you see or grab the cheapest fertilizer, but you really need to choose the right kind. Any fertilizer may help your hydrangea grow, but you could end up with big bushy foliage with no flowers.
In case you’re in a hurry our top overall pick is Espoma Organic Holly Tone, but if you have time you should continue reading to find out what you need to look for in a great hydrangea fertilizer. This way your plants will pop and be the envy of the neighborhood.
Table of Contents
A Closer Look At Fertilizer
Fertilizer is one of those innocuous things that we just pick off the shelf without really thinking about it. The pictures on the front show big, beautiful blooms, or gorgeous, plump, juicy looking vegetables. So we pick them according to that.
The packages have three numbers somewhere on the package. It may seem like the higher the numbers the better the fertilizer is, but let’s take a deeper look at the numbers and what they mean.
The three numbers on fertilizer all stand for the amount of nutrients in the container. They can range from 0 to around 30. They represent the NPK numbers.
If you see a container of fertilizer with the numbers 10-10-10, it means that 10 percent of the ingredients are nitrogen (N), phosphorus (P), and potassium (K). The rest of the ingredients are fillers or inert additives related to helping the nutrients get dispersed in the soil.
These fertilizers are all-purpose plant foods but you can also get fertilizers that focus on one nutrient. Grass fertilizer usually has a high N number, but low or zero P and K.
How NPK Affects Plants
Each nutrient in fertilizer feeds a part of the plant. Plant food with a high N count will produce big, leafy plants, and lush, green lawns.
P is phosphorus, and it works to grow thick roots and helps fruit and flower production. Fertilizers that focus on big, showy flowers, and starter fertilizers will have a higher middle number.
The last number of fertilizers is associated with potassium, or K. This nutrient is good for the overall health of the plants. Potassium strengthens cell structure and can help plants withstand heat and cold without too much damage.
Start By Testing Your Soil
Before you start adding fertilizer to your plants, you should get your soil tested to see what nutrients are lacking. A comprehensive soil test can tell you if your soil is acidic, basic, or if there are high amounts of certain nutrients.
You can purchase your own soil test kits through garden centers, or online, but they aren’t very accurate or thorough. The best place to get your soil tested and analyzed is through your own county extension.
These tests are usually low in cost, or even free. They will tell you the pH, composition, and what nutrients you need in your soil.
This is extremely helpful when deciding what to plant. Take my yard for instance, I had big beautiful rose bushes with plenty of deep green leaves, but some wouldn’t bloom at all. A few put out a single bloom, but that was it.
It turned out that my soil was very high in nitrogen, but lacking in potassium and phosphorus. With some time and a few soil additives, I was able to lower the nitrogen and get some pretty rose blooms.
A soil test will help you find the right fertilizer for your plants. In my case, I needed fertilizer that didn’t have any nitrogen but was higher in P and K. Now let’s go over the acidity of the soil because flowers on hydrangeas can change color depending on the pH of the soil.
Pink Or Blue Hydrangea Flowers
There are over 70 varieties of hydrangeas, that range in color from green to white, to pink or deep, almost purple. Most hydrangeas will keep their flower color and fade slightly as the flowers age.
But, if you purchase a blue, or pink flowered hydrangea, they can change colors depending on the soil pH. Getting your soil tested will help you find out if your soil is neutral, acidic, or basic.
Acidic soil will cause blue flowers, while basic will give your bush pink flowers. Depending on what color you prefer, you can alter the color by adding lime (pink flowers), sulfur, or soil acidifier (blue flowers).
The flowers won’t change overnight, it may take a season to get them to alter their color, so be patient if you want a different color.
If you bought white, green, or other color hydrangeas, the soil pH most likely won’t affect the colors.
When adding lime, make sure you use pelleted, or dolomitic lime and not hydrated or caustic lime. Hydrated lime (calcium hydroxide) can cause severe skin burns if it comes into contact with your skin and water or sweat.
Dolomitic (calcium magnesium carbonate) lime is safer to handle, but you should still use proper PPE as instructed by the manufacturer’s recommendations.
Keep Hydrangeas In Pots
If all that sounds like way too much work and trouble, you can keep your hydrangeas in their pots. They will stay their same color until the nutrients get leached out. But with the right fertilizer, they will stay the same vibrant color.
Most potting soils are neutral to slightly acidic as most plants prefer a somewhat acidic soil. To keep those vibrant blues without having to add too much, just keep your hydrangeas potted.
During the winter you may need to bring them inside or place them somewhere that will prevent the roots from freezing. Hydrangeas are hardy in most US zones, but they will need their roots protected if they aren’t planted in the ground.
Different Types Of Fertilizer
With different strengths of fertilizer, there are also various forms. You can find slow release pellets, granules, liquid, spikes, organic, chemical fertilizers, and more.
Liquid fertilizers are designed to give a quick boost of nutrients right away but aren’t the best choice for hydrangeas. These are usually best for plants that like it dry or need a very well draining soil to prevent root rot.
Cacti, orchids, bonsai trees, and monstera plants can benefit from liquid fertilizers.
Granules are usually added to water to make a quick release liquid fertilizer, while spikes go directly into the ground and slowly release a small amount of nutrients over a period of time.
When it comes to hydrangeas, a slow release, or organic compressed fertilizer is the best. They will get plenty of nutrients during the growth season to help them grow big, strong, and showy, and then when they are about to go dormant, they will get less.
Spikes can work also, but follow the directions on the package and be sure to only place them in the soil during the spring. Hydrangeas don’t need a lot of fertilization in the fall or during the winter.
Best Times To Fertilize Hydrangeas
When you bring hydrangeas home for the first time, you don’t need to worry about fertilizer. They are often packed with slow release fertilizer pearls in the soil. Just dig a hole about twice the size of the root ball, give it some rich soil mixed with your local dirt, and water it well.
Add a 3 to 4 inch layer of mulch and keep it watered for the first season. This will allow it to become established and grow a strong bed of roots.
Start Fertilizing Hydrangeas The Second Year
Either in late winter, or early spring, add some good fertilizer. When you start to see green from new shoots emerging from the plant, it’s a good time to add some much needed nutrients.
These plants grow fast and put on a big show, they need some food to do all that. This is the best time to fertilize. If you only add food for your plant once a year, this is the time to do it.
If you keep your plants in pots, a single spring feeding is best.
No More Fertilizer In August
Slow release fertilizer will typically feed your plants for up to 3 months. Some will continue to release nutrients for up to 6 months. If you use the latter, only fertilize once a year.
For faster releasing granules you can add more during the summer, but stop adding any fertilizer by early to mid August. Fertilizing late in the season can stimulate late season growth that can cause harm to the plant during the winter.
Some varieties of hydrangea set next year’s buds in “old wood.” If you fertilize too late in the season, these flowers could be stimulated to start growing, but when frost comes they will die off. This means you have fewer flowers next year.Â
How We Picked These Fertilizers
When choosing the best fertilizer for hydrangeas, we picked brands and types that would work best for these plants overall. Depending on your soil type, and what you want your plant to do, you may need to choose something that isn’t on the top of the list.
We picked granular, water soluble fertilizers that work best for overall plant health. We have included both organic and non-organic fertilizers. And of course, if you find something that you love that isn’t on this list, please go ahead and use it.
Best Fertilizer For Hydrangeas
For a great overall pick, you can’t go wrong with this acid based fertilizer. It’s a granular, organic fertilizer you can find in most garden centers that have a 4-3-4 NPK consistency that isn’t too strong for hydrangeas.
Espoma Holly Tone gradually increases the acidity of the soil for bright blue blooms. This fertilizer is also great, as the name suggests, for hollies, azaleas, blueberries, and other acid loving plants.
It’s a slow release fertilizer that will only need application twice a year.
Another acidic fertilizer with a 4-3-6 NPK rating also adds nutrients such as calcium sulfur, and magnesium. This fertilizer will feed your plants for a month and is also great for other acid thriving plants.
This is a 5 pound bag, and you’ll need to use a pound of fertilizer for each inch of trunk diameter, so it won’t last very long.
These pellets are coated in a semi-permeable resin that lets water in. The water then slowly dissolves the nutrients and releases them into the ground. All you have to do is sprinkle the suggested amount around the base of your plants and rake it into the top layer of the ground.
This fertilizer lasts up to 6 months long so you’ll only need to fertilize once per season. It usually comes in an 8 pound package so it will last if you only have a few plants.
It’s great for potted plants and in ground plants. The only con is the slow release of the nutrients. If you add these pellets in early spring, you may not see real results until late spring or early summer.
Miracle-Gro is a huge leader in the plant food industry. This option has an 8-8-8 NPK rating for even nutrient distribution. This is a good option for soils that don’t have a high amount of nitrogen, phosphorus, or potassium.
It’s also a water soluble fertilizer that provides an instant boost of nutrition as well as other nutrients such as copper, calcium, and iron. We mentioned before that these liquid fertilizers aren’t the best, but if you need a quick boost of plant food, we recommend this one.
The big con with liquid fertilizers like this one is you need to apply it very often. This brand needs to be added every 7 days during the growth season for the biggest, healthiest plants.
Bone meal is high in phosphorus and calcium and has an NPK rating of 6-8-0. If you have soil that is naturally high in potassium this is a great addition. Bone meal is good for big blooms, and healthy roots.
This fertilizer is a great additive for young plants as it gives them nutrition for a quick boost in root and foliage development.
You may be able to find this in your local garden center for much cheaper than what’s offered online.
Dr. Earth’s granules in their Acid Lovers Fertilizer are made of all natural ingredients such as bone meal, kelp meal, and alfalfa meal. They also feed for a whopping 6 months, so feed your hydrangeas once in early spring and you’re good for the rest of the season.
This option has a 3-4-3 NPK rating and helps lower the pH to make the soil more acidic for bright blue blooms. This formulation also contains beneficial microbes and plant probiotics.
The only problem with this product is the smell. The ingredients and the strong aroma could attract animals such as cats, dogs, or raccoons looking for a meal.
Another entry from Dr. Earth, this one contains slow release nutrients from ingredients such as fish bone meal, feather meal, rock phosphate, and potassium sulfate. It’s GMO free, organic, and it’s chicken manure and sewage sludge free.
Along with macronutrients such as 3-9-4 NPK, Flower Girl Organic fertilizer has plenty of micronutrients and probiotics which can help plants increase their drought tolerance.
These granules can feed plants for months, but it has been known to attract gnats, so you probably don’t want to use this inside, or near your house.
If you need to lower your soil’s pH, we recommend Espoma Organic Soil Acidifier. It contains sulfur which increases the acidity for hydrangeas, blueberries, evergreens, azaleas, and more.
It’s all natural, and slowly releases into the soil which helps to prevent burns. This formulation also has trace minerals that your acid loving plants will love. Again, this is for blue blooms.
If you love the bright pink hydrangea blooms, don’t use this product. The one con to this product is the time it takes for it to work. Unfortunately, it can take a few months to change the pH of the soil.
For those who have not purchased hydrangeas yet, you can get a head start and go ahead and apply this to the soil a few months in advance to get the process started. When you have plants that are already established, it may take between 3 months to a year for the change to take place.
Can I Use Compost?
Compost is a great addition to hydrangeas and probably all of your garden plants. You can purchase already processed compost from your garden center. You can find compost made from chicken or cow manure, from composted leaves and other materials, or a mixture. It’s all been “cooked” and is safe for use in your garden or around your plants.
You can even make your own compost easily. Gather up your fruit and veggie kitchen scraps and throw them into a pile, or a large, aerated container. Add in some leaves, untreated, unpainted wood chips or sawdust, or grass clippings as well.
Try to keep it a 50/50 mix of kitchen scraps and clippings or leaves so it breaks down faster and doesn’t cause an odor. Dampen it, turn it every few days for aeration, and in 6 months to a year you have a rich, all natural fertilizer and soil amendment for your plants.
Hydrangea Planting Tips
In most climates, hydrangeas prefer the morning sun or a partly shady spot in the garden. They usually don’t tolerate the intense evening sun. If you can place them somewhere where they get morning sun, and then are shaded the rest of the evening, they should do well.
They also like a well drained, rich, loamy soil. If your soil is like mine and nearly as hard as concrete because of the clay content, a good clay breaker additive, or plenty of compost mixed in should help your hydrangeas grow better.
Compact soil can cause root rot, or stunted growth as the roots have to work harder to get through the dense soil.
When you are trying to alter the pH of your soil, you don’t have to constantly have it tested as you try to reach the right levels. Instead, you can purchase a soil tester from your nursery or garden center.
These aren’t quite as accurate as a soil test, but they can help you get within the ballpark figure you’re looking for.
FAQs
What is the best time to fertilize hydrangeas?Â
Try to fertilize your hydrangeas when you see new growth after their first period of dormancy. Late winter or early spring is a good time to search for new growth.
Be sure to follow the recommended intervals and err on the side of giving less fertilizer as opposed to more. Hydrangeas that are just planted in the ground don’t need fertilizer as it’s usually added to the soil mix when you get it from the nursery.
When do hydrangeas start to bloom?
Hydrangeas bloom in the summer. Depending on the zone you live in, they may bloom in early or late summer.
How do I fertilize hydrangeas?
Be sure to follow the manufacturer’s recommendations. Some fertilizers require dilution in water or need to be worked into the soil. Some fertilizer releases nutrients very slowly, while some can give plants a quick, early boost of nutrition.
What does Epsom salt do for hydrangeas?
Epsom salts add the essential nutrient, magnesium. If your soil is lacking in this nutrient, a small amount of Epsom salts added to the soil could improve the fertility. When you add a little bit of Epsom salts to your plants—as long as they need it—it can increase the colors of your blooms.
Be sure not to add too much, and don’t add Epsom salts if your soil isn’t deficient in magnesium as too much can cause toxic soil buildup and inhibit calcium absorption.
The Verdict
Overall, if you are looking for a good fertilizer for your hydrangeas, Espoma Organic Holly Tone is a great choice. Before choosing a fertilizer, you should try and get your soil tested to make sure you aren’t adding nutrients that you don’t need.
Depending on the type and color of your hydrangeas, the soil pH could alter the color of the blooms so be sure to use a ph tester. Many gardeners prefer blue blooms and so they want an acidic soil. If you bought a white blooming hydrangea, then the pH of the soil won’t matter as the plant will keep the white blooms.
You don’t have to fertilize a new hydrangea. Let it grow and get established before adding fertilizer. Start fertilizing when you see new growth emerge and follow the instructions until August. Don’t add any nutrients after August so you reduce the risk of late frost damage.
By following these instructions and picking one of these recommended fertilizers, you should have big, showy hydrangea blooms each summer.
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