The nutritional needs of the hydrangea
Hydrangeas are among those plants that have very special demands on the soil and have a relatively high need for nutrients. The shrubs need a lot of nitrogen and potassium, as these nutrients have a direct influence on flower formation. In addition, the plants must be adequately supplied with minerals such as iron, sulfur, manganese and zinc, as these are often not available in sufficient quantities in the soil.
- When is the best time to use the hydrangea?
- How is the hydrangea properly overwintered?
- How is the hydrangea cared for after flowering?
In order to meet the nutritional needs of the hydrangeas, the plants must be fertilized with a nitrogen-based chemical or organic complete fertilizer that also contains little phosphorus. Many commercially available universal fertilizers are unsuitable for flowering plants because the phosphorus content of these agents is far too high. In the case of blue hydrangeas, this means, among other things, that the flowers turn pink or pink again.
Mineral fertilizers: Convenient to use
Special mineral fertilizers for hydrangeas are available from well-stocked specialist gardeners. Alternatively, special fertilizers for rhododendrons or azaleas are also suitable. These fertilizers optimally supply the hydrangea with all the nutrients required for healthy plant growth and abundant flower formation.
Because the fertilizer is well incorporated into the soil, the necessary nutrients are immediately available to the plant. However, this has the disadvantage that the fertilizing effect can decrease after a short time. Uniform supply of the plant can only be ensured if fertilization is carried out regularly and precisely according to the manufacturer's specifications.
Liquid special fertilizers for hydrangeas are very suitable for feeding potted plants. Fertilize regularly as indicated on the packaging in order to optimally supply the plant with all nutrients.
Organic fertilizers - the natural alternative
More and more garden lovers want to forego the use of chemical fertilizers and therefore prefer to use organic fertilizers. These provide the hydrangea with all the nutrients it needs over a longer period, but need some time to work optimally. For this reason, you need to plan carefully when to fertilize with organic fertilizers. Organic fertilizers are environmentally friendly and, since many of the products can be produced in-house, they are an inexpensive alternative to other fertilizers.
Horn shavings and horn meal
These fertilizers are made from beef horns and beef claws that have been crushed or ground.
- Horn meal: grain size less than one millimeter
- Horn semolina: grain size from one to five millimeters
- Horn shavings: (€ 6.39 at Amazon *) grain size over five millimeters
The nitrogen content of this fertilizer is around 12 to 15 percent, the phosphorus content is less than one percent. Horn shavings first have to be opened up by the organisms in the ground and only slowly decompose. Over-fertilization is almost impossible. The decomposition time for horn meal is a few days, coarse horn shavings need several months until they are completely broken down.
In order to optimally supply the hydrangea with all nutrients, we recommend spreading horn shavings on poor and dry soils in combination with humus.
Humus: nutrient-rich, deep black compost soil
Humus is a highly effective garden fertilizer that tiny microorganisms produce from garden and green waste. Within a year, the correctly set compost turns into a pleasantly fragrant, moist, crumbly and very nutrient-rich substrate that you can work directly into the soil.
Hydrangeas love coffee grounds
Coffee grounds contain many minerals and, when applied regularly, shift the pH of the soil into the acidic range preferred by hydrangeas. Worms and microorganisms also love coffee grounds, so the soil structure is noticeably improved with this fertilizer.
However, it is not enough to sprinkle the coffee grounds around the hydrangea. Work the fertilizer well into the soil so that it can develop its full effect.
Special fertilizer colors the flowers blue
Hydrangeas bloom pink, white or red without special fertilization. The coveted blue coloration only occurs when aluminum compounds and potassium alum are present in the soil and the substrate has a pH value of 4.0 to 4.5.
How to ensure that your blue hydrangea keeps its beautiful color:
- Special flower fertilizers for the blue color are only effective for pink-flowered varieties
- The pH value of the soil must not exceed 4.5 (test strips)
- The pH value can be shifted to the desired acidic range by using rhododendron soil.
- Only water the hydrangea with rainwater.
The right time to apply hydrangea blue is spring. Constant application of fertilizer according to the instructions on the packaging is necessary, otherwise the flowers will gradually turn pink again. However, these two-tone flower balls can look very special.
The right time for fertilization
When the days get longer again and the stronger spring sun warms the ground, this is the ideal time to supply the hydrangea with fertilizer for the first time of the year. Loosen the soil around the plants with a digging fork and lift some humus into which you have mixed horn shavings. Since the horn shavings decompose only slowly, it is sufficient to fertilize the hydrangea a second time in June.
Alternatively, you can fertilize outdoor hydrangeas and hydrangeas in tubs with a mineral long-term fertilizer in spring and early summer. You should also work these fertilizers into the soil.
Smaller potted hydrangeas have to be watered regularly with liquid fertilizer once a week during the growing season, which extends from March to August.
All hydrangeas, regardless of whether they are grown in pots or outdoors, should only be fertilized until the end of the growing season at the end of August. This is the only way for the shoots to fully mature by the beginning of winter. If fertilizing is too long, sufficient shoot closure is not guaranteed and there is a risk of frost damage.
Under no circumstances fertilize hydrangeas with blue grain!
Blue grain is one of the fast-acting complex fertilizers and is relatively inexpensive. The fertilizer contains as much phosphorus as nitrogen and is therefore completely unsuitable for fertilizing hydrangeas. Blue hydrangeas that are fertilized with blue grain turn pink again within a very short time. In addition, blue grain flows very uncontrollably. Therefore, if possible, avoid fertilizing the neighboring plants of the hydrangea with blue grain.
Tips & Tricks
Hydrangeas often suffer from chlorosis caused by iron deficiency. This trace element is hardly present in many soils. Iron chelate fertilizers and rainwater pouring can help.