When it comes to perennial shrubs with ornamental floral value, hydrangeas are the undisputed leaders. Her long flowering time, massive flower heads and opaque dense foliage are almost unmatched, making her a popular choice among home and professional gardeners around the world. Hydrangeas are often used as flowering hedges or for planting on facades. They are able to add a lot of visual interest to large and bare garden areas within a few years. Hydrangeas are not without drawbacks either, as these ornamental shrubs are notoriously nutrient hungry and will not flower if neglected the previous year. Therefore, we would like to dedicate today’s article to the topic of how to properly fertilize hydrangeas.
Here we show you tried and tested techniques that not only guarantee a long-lasting flowering period, but also improve bud density and abundance. In addition, we also share clever tricks on how to change the color of your hydrangea flowers from blue to pink or vice versa. Have we aroused your interest? Then read on!
Hydrangeas are beautiful but also demanding
When, with what and how often should you fertilize your hydrangeas?
Many ornamental plants do not require fertilizer at all to thrive in the garden. Hydrangeas are not one of them. These large ornamental shrubs draw many nutrients from the soil to produce their impressive, huge flowers and foliage each year. Therefore, they need to be fertilized two to three times a year – once in early spring, right after the last frost, once just before flowering begins, and the last time in late summer.
Also, for all these stages of hydrangea development, you need to use three different fertilizers. The first aims to wake the plant from its hibernation. The second, on the other hand, aims to help her produce the maximum amount of luscious and colorful buds. The third fertilization is not absolutely necessary, but recommended, because it improves winter hardiness. Let’s break down all three into their respective categories for simplicity.
Here you will find the answers to all questions about fertilizing hydrangeas
First fertilization
As mentioned, the first fertilization of your hydrangea is to help it wake up from its hibernation and start developing lush foliage and a strong root system. The best time to fertilize is between March and May after the last frost. This task requires the use of a slow-release fertilizer that will continuously feed the shrub over the next few weeks. Aggressive liquid fertilizers can easily burn the delicate spring roots. Brown leaves and stunted growth are usually the first signs of over-fertilization.
Over-fertilized plants often appear burnt
There are several slow release granulated products on the market that give excellent results. Certain fertilizers, such as compost or worm castings, are also easy to make at home. However, the preparation has to start the year before so that they are ready for use in the spring.
If you are using good mature compost or worm castings, apply as you would a mulch. Spread it in a thick layer (at least 5 cm) around your plant, press lightly and water thoroughly.
If you use granulated slow-release fertilizer, then it is best to buy a nitrogen-rich compound fertilizer (green manure). You can also use a balanced fertilizer with a 10-10-10 NPK ratio. Lightly rake the soil around your hydrangea, then sprinkle a handful of granular fertilizer just around the crown eaves. Cover the pearls with a layer of mulch or soil, then water thoroughly to activate them.
Granules vs Compost – Which Fertilizer to Choose?
Hydrangeas don’t look particularly impressive in spring
Distribute the compost or worm castings evenly
Granules, on the other hand, should only be scattered around the crown eaves
Second fertilization
The second time hydrangeas should be fertilized is just before they open their flower buds. The time can differ between the different species, varieties and their living conditions. The most popular species, the garden hydrangea and snowball hydrangea, usually bloom from June to September.
For this task you need a fertilizer that can be quickly and efficiently absorbed by the plant. Therefore, choose a liquid, phosphorus-rich fertilizer (flowering fertilizer). A 10-30-20 NPK ratio works best during this time. Dilute according to product directions and add to water to speed up absorption.
Would you like to do without chemicals? Then just use compost tea
Fertilize before the buds open
Third fertilization
As already mentioned above, a third fertilization is usually not necessary. However, if your hydrangea has suffered frost damage in previous years, don’t skip this step. This third fertilization not only makes the plant hardy, but also less sensitive to various pathogens.
For this third and final fertilization, you must use a potassium fertilizer in late summer, but not after August. Fertilization must be stopped at least two months before the first frost. In autumn, hydrangeas prepare for winter dormancy. So if you encourage new growth, it will not survive the winter and result in stunted growth the following year.
Almost all garden plants need potassium to survive the winter
Fertilize hydrangeas and thereby change the flower colors
You may have heard that hydrangeas can change color depending on the pH of the soil. That’s true, but only applies to varieties of garden hydrangea (Hydrangea macrophylla) and only if they already have a blue or pink hue. Colors included are violet, lilac and lavender, but not white. The latter is not affected by soil pH. The plant must also be at least 2 years old, otherwise the sudden imbalance of the soil could quickly kill it.
Blue flowers thrive in acidic soil with pH levels below 5.5. Hydrangeas in neutral and alkaline soils with a pH above 6.5, on the other hand, will produce pink flowers. A balanced pH of between 5.5 and 6.5 results in purple buds—a mix of blue and pink.
Blue vs Pink – Which Color Goes Better With Your Custom Garden Design?
To lower the pH, apply liquid aluminum sulfate around the crown eaves in March. Repeat again in April and one last time in May. To raise the pH simply add some lime to the soil.
Always mix and apply both products according to product directions and don’t overdo it. A change in flower color can occur within a few months or over the next year. Impatience and overfeeding can easily kill your plant.
There are now also pre-mixed products on the market
If you want to enjoy lush flowers and dense foliage year after year, then you need to fertilize your hydrangeas correctly and in good time. While these ornamental shrubs are not particularly undemanding, your effort will be well rewarded.
Fertilizer quantities must of course be suitable for potted plants
Summer floral arrangements are truly incomplete without hydrangeas
