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‘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
 | botanical name Hydrangea macrophylla |
|---|---|
 | genus Hydrangea |
 | plant type Deciduous shrub |
 | bloom colors Blue, Pink |
 | sun requirements Partial Sun |
 | water needs Medium |
 | height 4′-6′ |
 | spacing 70″ |
 | hardiness zones 6-9 |
 | soil needs Acidic |
 | 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’
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.
Propagation
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
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!
Sunlight
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.
Water
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.
Soil
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
‘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.
Fertilization
‘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
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.
Maintenance
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.
Pruning
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.
Pests
‘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.
Diseases
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
‘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!
