The richly flowering hydrangea needs a lot of nutrients to thrive and produce plenty of flowers. If the hydrangea produces a lot of foliage but hardly any flower umbels, you may have meant too well with the fertilizer.
How do you know if a hydrangea is overfertilized?
Over-fertilized hydrangeas (Hydrangea) often develop lush foliage but only a few flower umbels. Too much nitrogen can stunt plant growth and make them more susceptible to fungal diseases. To resolve this, you should perform a soil analysis and adjust fertilizer if necessary.
A lot doesn't always help a lot
In many gardens there is more of a nutrient surplus than a nutrient deficiency. In particular, the phosphorus content of many soils is extremely high. An excess of nitrogen means that the shoots do not mature sufficiently. The hydrangea becomes sensitive to fungal diseases.
Even if the soil has an excess of a certain nutrient, that does not mean that all nutrients are in abundance. For example, in many gardens there is a deficiency of important trace elements such as iron, potassium or manganese.
If over-fertilization is suspected, first analyze the soil
Since you cannot tell from the soil what nutrients are present, it is recommended to have a soil sample examined in a laboratory from time to time. If you suspect that the hydrangea is not thriving due to over-fertilization, you should only use an appropriate mineral fertilizer after this analysis. You will often receive fertilizer recommendations as an attachment to the soil analysis.
Two fertilizer applications per year are enough
Fertilize the hydrangea with a nitrogen-based special fertilizer (€8.00 on Amazon) with a low phosphorus content. You can find the composition of the fertilizer on the packaging. Commercially available NPK fertilizers should have a ratio of approximately 8+5+7 and also contain the trace elements magnesium and iron.
Fertilization should be carried out in spring and a second time in early summer. For garden hydrangeas, it is preferable to use solid fertilizer that you work well into the soil. Potted plants that have a higher nutrient requirement are supplied with a special liquid fertilizer for hydrangeas during the growing season from March to the beginning of August.
Prefer organic fertilizers
Naturally grown fertilizer such as compost or coffee grounds must first be decomposed by microorganisms so that the nutrients are available to the plant. As a result, these fertilizers sustainably improve the soil in the long term and promote plant growth. However, you cannot compensate for a nutrient deficiency in a short time with these fertilizers.
Tips & Tricks
Since the microgranisms work depending on the temperature and weather conditions, the same amount of nutrients is not always available. This means that the risk of over-fertilization is significantly lower than with mineral fertilizers.