How to Grow and Care for Hydrangea ‘Nikko Blue’

Are you thinking of adding a Hydrangea 'Nikko Blue' to your garden landscape this season? There are many qualities that make this particular hydrangea variety a popular choice amongst gardeners. In this article, gardening expert and hydrangea enthusiast Jill Drago shares everything you need to know about this type of hydrangea, including maintenance and care.

Hydrangea Nikko BluemGrowing in garden with bright colored flowers.


‘Nikko blue’ is a variety of big leaf hydrangea. These shrubs are used in a traditional cottage or coastal setting creating a soft yet dramatic appearance in gardens.

Of course, blue is in the name of this hydrangea variety. But in my opinion, it is the most perfect blue I have ever seen on a plant. Blue can be such a tricky color to obtain in your gardens. Aside from annuals, blue flowers can be hard to come by. Lucky for all of us we have the ‘Nikko blue’ hydrangea to fill our shady garden spots with dreamy blue hydrangea flowers.

If you are seeking more information on ‘Nikko blue’ hydrangeas or are just brushing up on what you already know, read on! I will cover everything you need to know about how to plant, grow and care for a ‘Nikko blue’ hydrangea.

About ‘Nikko Blue’ Hydrangea

Close-up of a blooming 'Nikko Blue' variety. The flower head is large, consisting of many small blue four-petalled flowers with slightly whitish centers.
Nikko blue is a delightful blue hydrangea with dozens of small inflorescences.
botanical-name botanical name Hydrangea macrophylla
genus genus Hydrangea
plant-type plant type Deciduous shrub
bloom-colors bloom colors Blue, Pink
sun-requirements sun requirements Partial Sun
water-needs water needs Medium
height height 4′-6′
spacing spacing 70″
hardiness-zones hardiness zones 6-9
soil-needs soil needs Acidic
pet-toxic pet toxic Toxic to dogs and cats

‘Nikko blue’ hydrangeas have become the standard that all other blue hydrangeas are judged against.  This pretty hydrangea is a member of the bigleaf hydrangea species or Hydrangea macrophylla.

The blue flowers on this shrub will grow up to 5 inches and will be made up of various shades of blue and white depending on how old the flower is. These flowers are mopheads and will be made up of dozens of smaller florets.

Why You Should Plant ‘Nikko Blue’

Close-up of a flowering 'Nikko Blue' variety in the garden. The bush is large, lush, has tall erect stems with large, heart-shaped leaves of bright green color with jagged edges, and has large flowers of apical, round blue inflorescences.
One of the advantages of this variety is that it is easy to care for.

If you are looking for blue flowers for your shady garden, ‘Nikko blue’ is a great choice for you. This type of hydrangea can grow to about 6 feet in height making them large, but not too large. You can easily use these for hedges or container plantings.

Another benefit of this blue beauty is that is relatively easy to care for. Aside from watering, ‘Nikko blue’ does not require much maintenance from you. It is rare to find such a beautiful shrub that requires so little from you.


Close-up of cuttings of a bigleaf hydrangea in a woman's hand, against a blurred background of small, plastic, black pots with soil. Cuttings have several young oval leaves of bright green color with serrated edges.
This variety can be propagated by softwood cuttings.

Do you already have ‘Nikko blue’ hydrangeas growing in your garden, but want more? If so, propagating these pretty shrubs is easy! The most successful way to propagate ‘Nikko blue’ hydrangeas is by taking softwood cuttings or by ground layering right in your garden.

Softwood cuttings should be taken in late spring to early summer. Select a 6-12 inch section of fresh green growth that has at least a few sets of leaves on it.

Dip the end of the cutting into some rooting hormone powder and stick the cutting into some sterile planting soil. Once the cutting has formed roots you can plant it in your garden, or you can continue to transplant it into larger pots until the hydrangea has grown a bit.

Garden layering is a very simple and fun way to propagate new hydrangeas. Select a low-growing branch and remove some of the bark and leaves.

Dig a shallow hole and place the branch in the hole, keeping it weighed down by a stone or brick.

Cover the branch with soil. Roots will form from the exposed growth points, at this point you can cut the branch from the mother plant and transplant this new hydrangea to another area of your garden.

How to Plant

A gardener transplants large-leaved shrubs from containers into the soil. Close-up of a woman's hands in black gloves with an orange rim planting a young hydrangea seedling in a dug hole in the garden. Nearby on the ground, there is another hydrangea seedling in a black plastic pot. Hydrangea seedlings have large oval leaves with serrated edges.
Choose the right spot in your garden and dig a hole twice as wide and as deep as the hydrangea root ball.

Just as caring for ‘Nikko blue’ is simple, so is planting the shrubs themselves. Once you have brought your hydrangeas home from the garden center arrange the potted hydrangea where you think you want to plant it.

Take a few steps back, and make sure you are leaving enough space between plantings so that everyone will thrive. Once you are confident in your placing, dig a hole about two times as wide and deep as the root ball of the hydrangea.

Gently place the hydrangea in the hole and spin it around so the best side of the plant is facing outward. Backfill with your garden soil, and water thoroughly.

You will want to check the moisture level of the soil daily for a few weeks, especially during any hot stretches. This will help prevent any transplant shock which can lead to the loss of the hydrangea.

How to Grow Hydrangea ‘Nikko Blue’

If you are ready to grow ‘Nikko blue’ in your garden, let’s take a look at the nitty-gritty of how to grow the happiest hydrangeas possible!


Close-up of a flowering bush in a sunny garden against the sky. The bush is large, lush, has tall stems covered with large oval green leaves with serrated edges and large round inflorescences of small blue flowers.
This hydrangea prefers to grow in partial sun, getting about 4-6 hours of sunlight per day.

This variety grows best when it is planted in partial sun. This is about 4-6 hours of sunlight. It is even better if this sunlight is in the morning rather than in the afternoon when the sun is stronger.

Bigleaf hydrangeas tend to dry out in the afternoon, you may even notice the leaves drooping toward the ground. If they pop back up after the sun has set your hydrangeas will be safe, if not they will need more watering or to be transplanted.

Sunshine is required for hydrangeas to produce big beautiful flowers so do not plant in deep shade. This could result in leggy growth and small or no flowers.


Close-up of a beautiful blooming shrub covered with water drops, in a sunny garden. The hydrangea bush is large, lush, consists of many erect stems with large, heart-shaped, green leaves with serrated edges. Hydrangea has a large rounded inflorescence of many 4-petal flowers with white eyes.
Water your hydrangea at the base of the plant.

Hydrangeas do best when they get around one inch of water per week. This water can be from rainfall, irrigation, or a combination of both.

When watering your hydrangea by hand, aim the water or irrigation sprinklers at the base of the plant. This will help to eliminate any fungal diseases on the leaves. It will also ensure you are using less water by saturating the soil rather than the leaves or flowers.


Close-up of planting 'Nikko Blue' variety in a garden, in well-drained soil. A woman's hand pours soil at the base of a freshly planted hydrangea seedling. A young hydrangea bush has beautiful, oval, bright green leaves with jagged edges.
This variety requires well-drained soil that retains some moisture.

For ‘Nikko blue’ hydrangeas to grow best they need well-draining soil canty to hold on to a bit of moisture. If you have soil that tends to pool or dry out too quickly you may need to amend your garden soil with some compost or other organic material.

Hydrangeas also prefer slightly acidic soil. You can find out the acidity of your garden soil by having a soil test done.

This will give you the soil’s pH and other information about the nutrient that naturally exist in your garden. Acidic soil has a pH of 6.5 or less. If your pH is higher than that your hydrangea will still grow nicely but amending it will allow the shrub to thrive.

Climate and Temperature

Close-up of a large 'Nikko Blue' variety in a sunny garden. The bush consists of tall erect stems, covered with large oval leaves of bright green color with serrated edges. Large apical rounded inflorescences consist of dozens of blue flowers.
This variety grows well well in zones 6-9 and do not tolerate cold and dry climates well.

‘Nikko blue’ hydrangeas are hardy in zones 6-9, sometimes you can get away with planting them in zone 5. This means that these hydrangeas are not the most cold hardy species of hydrangea.

If you plant in an unprotected area you may experience some winter burn. This variety is tolerant of the humidity of the summertime but may have a difficult time in more arid climates.


'Nikko Blue' variety blooming in the yard. Close-up of a large flower head consisting of several rounded apical blue-purple inflorescences. Some flowers are dry, brown. The leaves are large, heart-shaped, green with pointed tips and serrated edges.
When fertilizing, use a 10-10-10 all-purpose fertilizer.

‘Nikko blue’ hydrangeas do not necessarily need fertilizer. Depending on the results of your soil test, you may be able to skip this step. However, you may choose to fertilize your hydrangeas in the spring which can be beneficial.

If you choose to fertilize your shrubs a second time keep in mind that this second fertilizer application needs to be done before the end of September. This will prevent the hydrangeas from producing any new growth too late in the season which could be damaged by frost and other winter weather.

You can use an all-purpose fertilizer, such as a 10-10-10 on your hydrangeas. If you are looking to boost your blooms you may opt for a fertilizer with a higher middle number. This number represents phosphorus which is key for flowering.

If you would rather stay away from traditional fertilizers adding compost to your garden beds is a great way to naturally add nutrients to your gardens resulting in healthy and happy plants.

Changing Bloom Colors

Close-up of a hydrangea inflorescence changing from blue to pink. Large round inflorescence of dozens of small 4-petalled blue and pink flowers.
Your hydrangeas may change colors to pink depending on the pH level of your soil.

Now you would not be crazy to expect your ‘Nikko blue’ hydrangeas to have well, blue flowers! Sometimes though, your blue flowers might turn out to be pink! There is an easy answer to this, and it all lies in the pH of your soil.

For your hydrangea to have blue flowers the soil needs to be acidic. Pink flowers are a sure sign of alkaline soil. Now you can either leave nature to do its own bidding, or you can treat your soil with aluminum sulfate.

There are all sorts of products on the market that were created especially for this purpose. You will want to read the application instructions carefully to make sure you are giving your shrubs the right amount of aluminum sulfate to get the result you are looking for.


Close-up of a flowering 'Nikko Blue' variety in a neat garden. The hydrangea bush is large, lush, has large oval green leaves with serrated edges and large rounded flower heads, consisting of small blue and purple flowers.
Keep your hydrangeas clean by weeding and raking up fallen leaves.

It might seem hard to believe but this variety does not require much regular maintenance from you. Pruning is optional (more on that later), as is deadheading.

The best thing you can do for your hydrangeas is to keep the areas around them as tidy as you can. This may mean weeding or raking out any fallen leaves or other plant debris from your garden.

Later in the fall or early in the spring carve out some time to clean out the crown of the plant. Hydrangeas are really good at catching fallen leaves, these leaves can then compact and could lead to some fungal issues. Wear gloves and eye protection and grab out as much of the leaf debris as you can.


Close-up of a woman's hands in red gloves cutting a blooming shrub with red secateurs, in a garden. The hydrangea bush has large, lush, oval foliage, dark green in color with jagged edges. A beautiful, large, rounded apical inflorescence consists of dozens of small 4-petal flowers.
This variety does not need regular pruning, only in the case of shaping it.

When it comes to pruning, you will need to do a little bit of planning. These hydrangeas bloom on old wood. This means that your hydrangea will form buds for the next year shortly after this year’s flowers have passed.

Luckily, your ‘Nikko blue’ hydrangea does not require much pruning, if any at all. But if you do find that your hydrangea has gotten a bit bigger than you would like, or you just want to do some shaping you should do this in the early fall.

You can even do your pruning as you deadhead your flowers. This will safeguard you from accidentally snipping off any of those precious buds.


Close-up of a Japanese beetle on blue flowers. The beetle is large, shiny, metallic green.
The most common pests are Japanese beetles, aphids, and spider mites.

‘Nikko blue’ does not have too much difficulty when it comes to pests. You will find common garden insects, however. Japanese beetles, aphids, spider mites as well as caterpillars can be found residing on your ‘Nikko blue’ hydrangeas.

These pests are common and you can find treatments for each of them at your garden center. You can also spray the hydrangea with your host to knock off some of the insects. Japanese beetles can be removed by hand and collecting them in a bucket of soapy water.


Close-up of a plant leaf infected with a fungal disease. The leaves are large, oval, green, with jagged edges, covered with purple-orange spots.
Hydrangeas can be susceptible to fungal diseases in warm and humid environments.

Hydrangeas do not have much trouble when it comes to diseases. If they struggle with anything though, it is fungal diseases. These types of diseases are most prevalent in warm and moist environments. You will notice them more if your plants are growing too close together. This can prevent sufficient airflow.

Diseases to look out for are leaf spot, blight, or powdery mildew. These can all be treated with a copper fungicide if needed. However, they are easily preventable by keeping your garden tidy and minimizing water splashes by watering at the base of the hydrangea.

Common Planting Locations

Close-up of a flowering bush under the wall of the house. The bush is large, lush, consists of erect stems covered with large, heart-shaped, green leaves with serrated edges. Large apical inflorescences of a rounded shape consist of many blue flowers.
These hydrangeas make a great addition to your perennial or container garden.

‘Nikko blue’ hydrangeas are simple to add to your garden. Try adding them into a perennial garden or a foundation garden for a big pop of blue color. This variety also makes a really pretty short hedge or border plant that can be accented by lower-growing perennials or flowering annuals.

And of course, don’t forget that these blue beauties can be added to your containers! Container-planted hydrangeas are a really good option for gardeners who may not have the right growing conditions in their yards.

You can easily place containers on a patio or porch to ensure that your plant is getting the perfect amount of sunlight.

Frequently Asked Questions

Why are my flowers pink instead of blue?

If your hydrangea is pumping out loads of pretty pink flowers when you expected them to be blue, you have alkaline soil. This can be fixed easily by applying some aluminum sulfate to your soil.

This trick only works if you are growing a hydrangea that is meant to be blue such as ‘Nikko blue’ or a hydrangea that is meant to be pink. If you have a white hydrangea you will not be able to alter the color of your hydrangea blossoms.

Why aren’t my ‘Nikko Blue’ hydrangeas blooming?

There are a few reasons that they may not be blooming.

The first is plant location. Bigleaf hydrangeas like to be planted in partial shade, not full or deep shade, nor full sun. They need a break from the sun to keep from drying out. However, by planting these shrubs in the deep shade your hydrangea will not be able to produce flowers. Consider transplanting to an area in your garden that receives dappled or morning sunlight.

The next is a pruning mistake! This variety forms their flowers on old wood. This means that the flowers for next year will be formed on branches in the fall prior. Pruning rarely needs to happen, but if you choose to do some pruning it should be done immediately after they have finished blooming to avoid snipping off any flower buds.

What should I plant with my ‘Nikko Blue’ hydrangeas?

‘Nikko blue’ hydrangeas thrive in partial sun sp when you are considering plants to grow nearby, you will want to keep that in mind. Hostas, astilbe, and shade-loving annuals such as impatiens are great starting points. If you would like to add some different textures to the garden consider adding ferns or lambs ear.

Final Thoughts

If you are looking for that perfect blue hydrangea ‘Nikko blue’ is the way to go. It is well-loved for its stunning color and its dependability. A hedge of this variety growing along the front of a house makes a perfect cottage foundation garden. There is nothing boring, or standard about this blue beauty, give it a try!

Limelight hydrangea blooming in spring with white flowers


How to Plant, Grow and Care For Limelight Hydrangeas

Limelight hydrangeas can make a wonderful addition to any garden. These beautiful shrubs grow quite tall with beautiful blooms. Because they are panicles, they are also surprisingly heat and sun tolerant. In this article, gardening expert and hydrangea enthusiast Jill Drago examines how to successfully grow Limelight hydrangeas and provide them with proper care.

Hydrangea Anomala growing in the garden with white flowers blossoming off the vines.


How to Plant, Grow and Care For Hydrangea Anomala

Are you looking for a unique hydrangea to plant in your garden this season? The hydrangea anomala may be slightly less popular than others, but it's no less beautiful. In this article, gardening expert and hydrangea enthusiast Jill Drago examines everything you need to know about the hydrangea anomala and their care.

hydrangea serrata


How to Plant, Grow and Care For Hydrangea Serrata

Hydrangea serrata is also known as 'Mountain Hydrangea" and slightly less common than more well known hydrangea species. But that doesn't make their blooms any less beautiful! In this article, gardening expert and hydrangea enthusiast Jill Drago walks through everything you need to know about hydrangea serrata, including planting, care, maintenance, and more!

early blue hydrangea


11 Reasons You’ll Love ‘Early Blue’ Hydrangeas

If you are thinking of planting 'Early Blue' hydrangea this season, you've come to the right place! There are many reasons to love this low-maintenance variety, especially with its beautiful blue blooms. In this article, gardening expert and hydrangea enthusiast Jill Drago walks through why she loves this popular hydrangea variety, and thinks you will too!

A close up of the hydrangea macrophylla growing in a garden with bright purple blooms. There are three clusters of flowers on this shrub. The cluster on the right is violet with blue at the center. The cluster on the left is less mature and similar in color, but with yellow at the flower centers. The third bloom is behind them out of focus.


How to Plant, Grow and Care For Hydrangea Macrophylla

Hydrangeas are one of the most common garden shrubs. Within their species, Hydrangea Macrophylla is one of the most popular types that gardeners decide to plant. In this article, gardening expert and hydrangea enthusiast Jill Drago walks through everything you need to know about this type of hydrangea and their care.

oakleaf hydrangea


How to Plant, Grow, and Care for Oakleaf Hydrangeas

Thinking of adding some oakleaf hydrangeas to your garden this season, but aren't sure where to start? This species is a favorite amongst many gardeners, so it's important to start off on the right track if you are adding them to your garden this season. In this article, gardening expert and hydrangea enthusiast Jill Drago walks through how to plant, grow, and care for Oakleaf Hydrangeas.