Ask the Plant Doctor! How to get hydrangeas to bloom in Malaysia

For hydrangeas, a balanced, slow-release fertiliser is usually the best option. Photo: 123rf.com

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Dear Plant Doctor,Q I have planted a few lowland hydrangeas of various kinds – they are leafy and healthy but they have not bloomed in all the three years I have been caring for them. The sellers promised flower clusters and I do see some others enjoying their successes. What should I do to encourage blooms other than using flowering hormones? – Margaret S.

Proper fertilisation of hydrangeas requires careful consideration of both the type of fertiliser and the application rate, as these factors significantly impact the health and blooming potential of plants.

In our tropical climate, it is crucial to choose the appropriate fertiliser and apply it correctly, considering the specific type of hydrangea, soil conditions and local environmental factors.

For hydrangeas, a balanced, slow-release fertiliser is usually the best option. These fertilisers typically have a Nitrogen-Phosphorus-Potassium (NPK) ratio near 10-10-10 or 20-20-20.

Alternatively, fertilisers designed for flowering plants, which typically have higher phosphorus content to encourage blooms, are also a good choice.

The recommended application rate for a balanced 10-10-10 fertiliser is approximately 20g per square metre.

When fertilising individual plants, approximately 120g of fertiliser around the drip line is generally sufficient. Drip line refers to the area directly beneath the branches of the outermost plant.

This method ensures that the fertiliser is distributed where the roots can most effectively absorb it.

When applying fertilisers, it is important to distribute them evenly around the drip line to avoid direct contact with the stems or trunks of the plants. After application, watering the fertiliser into the soil helps it to reach the roots more effectively.

Compost and mulch can also be used. They can generally be applied more liberally and should be applied to the soil around the plant.

It is essential to remember that over-fertilisation can be detrimental, leading to excess foliage at the expense of blooms, potentially harming the plant. Therefore, it is often better to err on the side of under-fertilisation rather than risk applying too much.