Nikko Blue Hydrangea: A Richly-Colored Blue Mophead Hydrangea

Bright and blue, Nikko Blue Hydrangeas are a wonderful way to add a pop of color to your yard or garden. There are many types of hydrangeas, but Nikko Blue adds a nice cool color tone to the mix.

Nikko Blue hydrangeas are deciduous flowering shrubs that bloom from early summer into fall. The blossoms are usually blue, but can also be purple or pink depending on the alkaline levels in the soil. They are great accent plants and have a longer bloom time than many plants. Nikko Blue is one of the most popular blue hydrangea cultivars available.

Whether you’re wanting to add this type of hydrangeas to your yard, or you’re just wanting to know more about these plants, it’s a good idea to have a good understanding of what these plants need in order to thrive. Read on to learn all about the Nikko Blue Hydrangea!

Nikko Blue Hydrangea
Nikko Blue Hydrangea (Hydrangea macrophylla ‘Nikko Blue’)

Nikko Blue Hydrangea: The Basics

The Nikko Blue Hydrangea is a cultivar of Bigleaf Hydrangea (botanical name Hydrangea macrophylla). These plants are native to Japan. They are also known as “Mophead” hydrangeas, which refers to their oversized blooms. As the name “Bigleaf” implies, the foliage on Mophead Hydrangeas like Nikko Blue is quite thick and large, so it adds a lot of ornamental greenery to the garden.

Bigleaf Hydrangeas are probably the most well-known types of hydrangea, and yet it’s the least resistant to cold. Nikko Blue Hydrangeas can be grown in Zones 6-9. These types of hydrangeas are deciduous shrubs that can grow to be 4 to 10 feet tall, and 4 to 10 feet wide, but they are usually at the smaller end of that scale (around 6 feet tall and wide). They are fast-growing and have large, round flower clusters.

The color of Nikko Blue hydrangea flowers, as you might have guessed, is typically blue. However, this is not always the case. One unique thing about this type of hydrangea is that the color of the blooms can change depending on the type of soil it is planted in.

Most of the time, these types of hydrangeas will be a rich, sky blue color. However, when they are planted in soils with higher alkaline soils, the blooms can actually be pink or even purple colors. The flower clusters are typically about 5 inches across. They usually bloom in the early summer and remain that way for about 2 months. These plants are very floriferous and typically produce new flower stems throughout the summer.

Buying Nikko Blue Hydrangea Plants

The following garden centers offer Nikko Blue Hydrangea plants for sale:

How To Grow Nikko Blue Hydrangeas

These plants grow quickly and typically grow to be around 6 feet tall and wide. The more shade this plant receives, the shorter it will live. These plants are perennials, meaning they will return year after year and continue growing if cared for properly.

Their flowers or blooms are actually called sepals and typically appear in July. They are tough and persist for months. Despite the name “Nikko Blue,” the color of these hydrangeas actually depends heavily on the pH level of the soil it’s planted in.

These types of hydrangeas should be planted in rich and moist soil, but it should also be well-draining soil. The nice thing about the pH levels controlling the color of the flowers is that you can very easily change that color. If planted in more acidic soils, the bush will bear blue flowers. If the soil is a more alkaline blend, pink or purple blooms are likely to occur. You can test your soil and add certain soil amendments to get the desired flower color.

These types of hydrangeas should be planted and grown in a spot where they have partial shade. This plant appreciates some morning sunlight, though too much sun can cause damage if you don’t keep it well-watered.

You should water new hydrangea plants deeply, and do it multiple times a week. This will help it to grow strong roots. In general, you should try and give these plants at least 1 inch of water per week. This should be increased as you experience hotter weather.

When watering these plants, you should make sure to water the base of the plant to avoid getting the flowers and leaves wet. This will help you to keep your plant healthy and strong by avoiding fungal diseases.

Where Do Nikko Blue Hydrangeas Grow Best?

This type of hydrangea grows best in growing zones 6 to 9, which covers many parts of the United States. These plants are native to Japan, but can, of course, be grown in other locations as well.

Mature hydrangeas can withstand temperatures as low as 32 degrees Fahrenheit. Younger plants, however, should not be kept at temperatures lower than 35 to 40 degrees Fahrenheit. In general, hydrangeas prefer average to high levels of humidity. They will typically thrive in the moist heat of summer.

If they are in a desert climate and are exposed to too much dry air, the leaves of the plant can wilt or droop. You can compensate for this by making sure the plant stays well watered and has access to shady areas. This type of shrub prefers a shady to partial shade location. It will grow best in these spots. Full sun can be tolerated by this plant as long as constant moisture or water is provided.

Nikko Blue Hydrangea

Pruning Nikko Blue Hydrangeas

These shrubs do not require much, if any, pruning. If you do feel the need to prune them, it’s important to know that these plants bloom on old wood. This means that this type of shrub blooms on the previous year’s growth. This also means that the right time to prune this plant would be in the summer, immediately after it finishes blooming.

These plants can be pruned after flowering and this can be done by cutting back the stems to a pair of healthy buds. You can also use the early spring as an opportunity to prune out weak or damaged stems.

Buds are usually set in late summer to early fall, so you need to prune before this if you don’t want to risk losing any flowers for the next year. If you prune after the buds have been set, that is what can happen. If there are any dead branches, those can be pruned out at any time. These branches should be pruned back to where you see healthy buds growing.

Nikko Blue Hydrangea plant
Nikko Blue Hydrangea plants are generally pruned in summertime, just after the plant has finished blooming.

Mary Jane Duford

Mary Jane is a home gardener who loves creating healthy, welcoming spaces (indoors and out!) - About Mary Jane (

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