To be able to develop their full bloom, hydrangeas have to be properly fertilized. You can find out when, how and with which fertilizer you should fertilize your hydrangeas here.
Hydrangeas (Hydrangea) are among the absolute classics in our gardens and have lost none of their special charm. In order to be able to benefit from their flowering dream, the hydrangeas must be supplied with nutrients on a regular basis. Because the nutrition of the hydrangea determines whether the plant is vital and sets the course for the development of the flower colour.
Any type of hydrangea can develop into a he althy and vigorously flowering beauty with the right fertilization. In addition, the basis for the flower color is laid for the popular farmer's hydrangeas (Hydrangea macrophylla). This is mainly influenced by soil pH and to a lesser extent by fertilization. In this article you will learn more about the blue coloring of the hydrangea flower and the following paragraphs will deal with when, with what and how to fertilize hydrangeas in beds and pots.
When is the best time to fertilize hydrangeas?
When planting, an organic long-term fertilizer should be incorporated. The slowly released nutrients and the activation of the soil life are a good basis for the establishment of the new planting at the new location. By the way, hydrangeas are planted either in spring (March - May) or in autumn (October - November). Established hydrangeas should be fertilized once a year outdoors and twice a year in pots because of the smaller substrate volume.
Tip: When planting new hydrangeas, remember that they like to be acidic to neutral. If you want to achieve peasant hydrangeas with blue flowers, you even need a pH value of around 4.5. Oak leaves, grape pomace, cuttings from rhododendrons and other ericaceous plants, as well as pine shavings or peat lower the pH for hydrangeas.
Fertilize hydrangeas in the bed
Usually are hydrangeasquite strong-growing and are therefore often planted in beds. If you use an organic fertilizer, one fertilization per year is all the effort you have to make to supply nutrients. However, this one fertilization should be between March and May, because late and high-nitrogen fertilization causes the plant to suffer frost damage - and the flowering to fail in the following year.
If you want to use a mineral fertilizer, it must be applied monthly and depending on the product recommendation. Long-term mineral fertilizers can save you this work. However, they are more likely to harm hydrangeas in the long term, as you will learn a little later.
Summary when to fertilize hydrangeas:
- Hydrangeas should be planted and fertilized when planted in spring or autumn
- Hydrangeas in the bed need to be fertilized with organic fertilizers only once a year (March - May)
- Fertilizing too late with nitrogenous fertilizers leads to failure of flowering in the following year or even to frost damage
- Fertilising with mineral fertilizers may be more time-consuming and not beneficial for the hydrangeas in the long term
Excursus: three reasons why your hydrangea is not blooming properly
- Pruning too hard: hydrangeas mainly bloom from last year's wood, which is why every pruning in spring only thins out and removes dead and frozen shoots
- Frost damage: last year's shoots have frozen back and the flowering sites have also been lost; Frost damage is often the result of too much or too late fertilization with nitrogen
- Too humid between June and August: the hydrangea thrives instead of flowering.
Fertilize hydrangeas in the pot
The same applies to planting potted hydrangeas as to outdoor hydrangeas. However, hydrangeas in the pot must then be treated a little differently than those in the field. On the one hand, their substrate volume is much smaller than that of their relatives. On the other hand, pot hydrangeas are often overwintered frost-free to protect the pots and plants. As a consequence, the pot hydrangea is given a two-part fertilization: It receives two thirds of its nutrients between March and May and the last third between June and August. Of course, this only applies if you are using an organic fertilizer that is not overly nitrogenous. With mineral fertilizerswith an emphasis on nitrogen, you should refrain from such a late fertilization and rather only fertilize regularly from March to June and according to the fertilizer manufacturer's recommendations for use.
Summary of fertilizing hydrangeas in pots:
- Potted hydrangeas should be planted and fertilized when planted in spring or autumn
- Potted hydrangeas need to be fertilized twice a year (March - May and June - August) with organic fertilizers
- Potted hydrangeas must be fertilized regularly with mineral fertilizers according to the manufacturer's recommendations - avoid nitrogen supply after June
What fertilizer is the best for hydrangeas?
Anyone who sees their garden as a growing and developing place to feel good should rely on fertilization that is as natural, long-term and sustainable as possible. However, this excludes purely mineral fertilization, because mineral fertilizers only satisfy the needs of plants in a very one-dimensional manner. They only provide nutrients, but let the quality of the soil suffer. For example, the humus content decreases. Since humus is an important water reservoir and hydrangeas depend on a good water supply, they ultimately suffer from mineral fertilizers - and you have to water them more and more frequently. The choice of organic or organo-mineral slow-release fertilizers, on the other hand, has the following advantages, among others:
- Maintenance or even increase of the soil humus content and thus the water retention capacity, nutrient storage capacity, root penetration and aeration of the fertilized soil
- Entry of important trace nutrients that are usually missing in mineral fertilizers.
- Resource-saving production of an environmentally friendly fertilizer for fertilization without serious consequences for people and nature
We have developed a hydrangea fertilizer that meets all of these criteria and even goes a little further: It is based on animal-free raw materials from the food, luxury food and animal feed industries as well as mineral components that are also used in organic farming. This makes our Plantura organic hydrangea fertilizer truly "organic" and therefore ideal for sustainable gardening.
Fertilize hydrangeas correctly: instructions for ideal application
When dosing fertilizer, you should always follow the manufacturer's specifications closely. Thisprevents your hydrangea from becoming deficient or showing symptoms of overfeeding. We can provide you with the following instructions for our Plantura organic hydrangea fertilizer:
- For new plantings, work 150 grams per square meter or 50 grams per plant into the bed or under the potting soil and the excavation of the planting hole.
- Water generously to loosen the fertilizer granules. This helps to start the conversion and thus the nutrient release.
- In the open field, annual fertilization is carried out between March and May with 60 - 80 grams per square meter or 25 grams per plant. The granules are worked in flat and then soaked well.
- Hydrangeas in pots are supplied with 3 - 5 grams per liter of potting soil in March/April, and with 2 - 3 grams per liter of potting soil in June/August. Work in flat and pour on if possible.
Tip: It is often not that easy to weigh the volume of a pot. Sometimes it helps to hold a bucket with a defined volume (e.g. a cleaning bucket with 10 or 20 liters) next to the pot and estimate its size.
Fertilize hydrangeas with minerals: Blaukorn & Co.
The application of mineral fertilizers is based on the assumption that a plant needs water, light and the 14 essential nutrients to live - nothing else. However, what was long considered certain has been refuted for several years: plants interact with the soil in which they grow in many different ways. Ninety percent of all terrestrial plants live in symbiosis with soil fungi (Mycorrhiza) to be able to take up water and nutrients more efficiently. In addition, a number of types of microorganisms settle around the roots, which feed on their excretions and in return release nutrient ions from the soil for the plant. These two examples show that soil is more than just a sponge for water and nutrients.
Of course, mineral fertilization is still possible. However, since it renders a number of biological processes in the soil superfluous and chemically unbalances them, a deterioration in soil quality is unavoidable if only mineral fertilization is used. Mineral fertilization is particularly unsuitable for hydrangeas: They need a flowing and needs-based supply of nutrients in order to develop frost-tolerant shoots and a lot of humus to cover their water requirements. Both are much easier to achieve with organic fertilization because it relies onnatural regulatory processes of the “soil organism”.
Fertilize hydrangeas with home remedies
As already mentioned, hydrangeas love an acidic location. For example, composted oak leaves, grape pomace and coniferous soil - i.e. the soil found under coniferous trees - are suitable for maintaining the acidic soil environment. You can also mulch the soil under hydrangeas with a mixture of oak leaves, pine shavings and some horn meal to stimulate the decomposition and release of acids. A mixture of chopped oak leaves, wet coffee grounds, pine wood shavings and needles and some horn meal is also effective. To determine the need for such an application, it is always advisable to test the pH of the soil beforehand. This can be done with a commercially available test kit or as part of a soil analysis.
The use of horn shavings or horn meal as the only fertilizer is not recommended, as these mainly contain nitrogen and phosphorus, but hardly any potassium. A small dose in spring, for example in connection with an acidifying mulch layer, can definitely be beneficial - but should always be supplemented with a full-fledged fertiliser.
Tip: Mulching hydrangeas offers a number of benefits which we have compiled in our special article.
Detecting nutrient deficiencies in hydrangeas
In the following we summarize common deficiency symptoms in hydrangeas and how you can recognize them.
Iron Deficiency in Hydrangeas
The symptoms of iron deficiency are intercostal chlorosis (yellowing of the leaf, the leaf veins remain green for a long time) on the youngest leaves. Iron is a micronutrient that is most readily available to plants when soil pH is low. Since the iron uptake strategy of hydrangeas is set to a low pH value, they quickly suffer from an iron deficiency if the soil is not acidic enough. Unlike some other plants, they simply do not manage to absorb it efficiently. The safest way to lower the soil pH value is to combine it with iron fertilization. Our Plantura organic hydrangea fertilizer therefore contains a small amount of iron to rule out an absolute deficiency from the outset. You can find more detailed information on iron deficiency in hydrangeas in our special article.
Nitrogen Deficiency in Hydrangeas
The symptoms of a nitrogen deficiency are chlorosis (yellowing of the leaves) on theoldest leaves. Nitrogen is “mobile” in the plant, so it can be moved. When there is a shortage, nitrogen is sent from the old, less important leaves to the youngest leaves. Nitrogen fertilization eliminates the deficiency, of the organic fertilisers, the liquid variants work the fastest.
Potassium deficiency in hydrangeas
Potassium deficiency shows itself in the form of the so-called "wilting", the foliage looks limp, despite sufficient water supply. Later, necrosis forms, starting from the leaf edges and tips. All symptoms appear first on the older leaves. A potassium deficiency can promote frost damage in winter. Fertilizing with potassium fertilizer usually fixes the deficiency quickly. However, it is important not to be overly frugal. Potassium is required by plants in large quantities and the storage locations in the soil should always be well stocked. Our Plantura organic hydrangea fertilizer contains sufficient potassium to effectively prevent a deficiency.
If you want to learn more about why special hydrangea fertilizers are necessary, you will find all the important information here.