Fertilizing hydrangeas – red, blue, white
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Current gardening tip: Fertilizing in spring and summer
Fertilizing hydrangeas correctly – for all types, varieties and colors
We exclusively offer an Ullmann Hydrangea Fertilizer that we have developed ourselves and that is suitable for all hydrangea species and colors .
This special fertilizer is used in nurseries for the cultivation of all hydrangeas and ensures:
- strong growth,
- healthy plant structure
- and a lush bloom.
Why targeted fertilization is so important:
Hydrangeas are among the most nutrient-demanding plants —especially during their main growth phase. Only a balanced nutrient supply ensures:
- strong shoots,
- healthy leaves
- and long-lasting, intense flower colors.
Mineral vs. organic fertilizers:
Mineral fertilizers are immediately available to plants – ideal for rapid nutrient supply.
→ Important: Fertilize evenly and frequently to avoid over- or under-fertilization.
Organic fertilizers also improve the soil, but they must first decompose – so their effect only begins after about 3-4 weeks .
The nutrients are released by microorganisms and thus made available to the plant.
→ Ideal: in spring to improve the soil .
Fertilization recommendations for hydrangeas in pots and outdoors
Hydrangeas in pots (balcony, terrace):
- March to August: apply liquid fertilizer once a week
- Adjust watering quantity depending on size and location
Planted hydrangeas in the garden:
- Start fertilizing in spring – directly at bud break
- Granulated fertilizer (e.g. Blaukorn): can be incorporated in spring – but with caution!
Important NOTE:
We do not recommend using fertilizers with a high salt content such as Blaukorn for hydrangeas!
These are:
- weather-dependent (uncontrolled flushing)
- often still active in autumn
→ This can lead to the shoots not ripening in time , which in turn can lead to the buds freezing in winter.
Fertilization stop from mid-August
Fertilization should be stopped from mid-August .
Reason: The plant must now mature , which means:
- Shoots become woody and
- Flower buds fully develop
This is how the plant can optimally prepare for autumn and winter :
- No more soft shoots
- No frost damage to new buds
- Safe start in the following year
Tip: Please also pay attention to our recommendations for overwintering hydrangeas to preserve their splendor.
The secret of the blue flowers
The species Hydrangea macrophylla – which includes many mophead hydrangeas – naturally displays flower colors in white, pink or red.
However, an intense blue flower color can only be achieved through targeted soil treatment .
Requirements for blue flowers:
- Acidic soil or potting substrate with a pH of 4.0–4.5
- Sufficient aluminum in the soil
How can this be achieved?
The required aluminum can easily be added via the watering system . The ready-to-use special preparation "Ullmann Hydrangea BLUE" is ideal for this purpose—soon available again in the Ullmann Hydrangea World shop.
The best way to check the pH value of the soil is with pH test strips – also available again soon in the shop.
If both conditions are met, nothing stands in the way of a brilliant blue bloom .
Good luck, healthy plants and a green thumb
wishes you
Your team at Hydrangea World Ullmann