Why do hydrangea leaves turn yellow

Hydrangeas: leaves curl up or turn yellow: what to do?

The flowers of the hydrangea bushes shine in white, natural, red, pink or blue from July to September. The over 80 different species come from East Asia, Chile and North America. With their wonderful flower power and a height of less than two meters, the shrubs are ideal for any garden size. If the leaves turn yellow or the leaves roll up, this can cloud the long-lasting bloom power and measures must be taken quickly. Otherwise this can spread over the entire plant and in the end just a new plant is the solution.


Wrong location

If the shrub is too sunny in the garden, the plant will roll up its leaves. A suitable shade provider should be considered here. If this is not possible, the shrub must be transplanted to a better location.

The upright hydrangeas are native to moist deciduous forests with soils rich in humus. If you want to enjoy richly blooming and healthy hydrangeas for a long time, you have to create conditions similar to those at home. In our latitudes, a partially shaded and wind-protected location should therefore be chosen. Large treetops provide the bushes with natural wind and sun protection through sufficient shade. A location under larger trees with a lush treetop such as the forest pine is ideal. Alternatively, the bushes can be protected from the sun with a white bed sheet on hot midday hours.

Wrong mildew

If the wrong location is not causing the leaves to roll, the hydrangea can be sick. As the “downy mildew” progresses, the leaves can curl up. Before that, a flour-like, dusty coating can already be seen on the upper side of the leaf. This can easily be wiped off the leaves. If no action is taken, the disease can spread further and the plant dies.

The causes of downy mildew can be:

  • too little light
  • too much nitrogen
  • high temperature differences
  • too close plant spacing

In addition to taking immediate measures to contain the fungus, the cause of the leaves rolling should also be eliminated. Removing weeds around the bush prevents the disease. With timely detection, you should follow the following instructions:

  • Remove the infested plants
  • Disposal in the household waste prevents the fungal spores from spreading further
  • treat the plant with diluted milk or whey
  • use fungicides in case of severe infestation

The microorganisms contained in milk and whey support the plant in fighting the fungus. When using fungicides, pay attention to the indicated dosage. Do not use fungicides that will harm ladybugs or wasps. These beneficial insects keep the fungus in check.

Tip: Plant garlic, basil or chives between the plants. These plants keep the downy mildew pathogens at bay.

Yellowing from chlorosis

If the leaves of your hydrangea turn yellow, the plant is sick. Yellow leaves are typical of leaf chlorosis. With this disease, the leaf turns yellow from the tip. Only the leaves change color, the leaf veins remain green. In the later stage the foliage turns brown. An iron deficiency is the cause of this disease, which is caused by an excess of lime in the soil. Due to the excessive lime content, the hydrangea can no longer absorb enough iron from the soil. Soils that are too cold must be acidified. The following are suitable for this:

  • Leaf compost
  • peat
  • Rhododendron earth

As an immediate measure, the deficiency should be compensated for with an iron fertilizer. Then you should regularly use a special hydrangea fertilizer.

Tip: The iron fertilizer is poisonous. Therefore only use it with protective clothing.

Yellow leaves from over-fertilization

Incorrect fertilization can also be the cause of yellow leaves. A lack of nitrogen leads to bottlenecks in the leaves and chlorophyll can no longer be formed. This green dye is needed for photosynthesis and is essential for survival.

This usually affects the entire leaf. First the older leaves turn yellow in the lower area, later the leaves that have driven back are also affected. The cause needs to be treated quickly. Because without further measures it can spread further and the flowers wither.

Tip: fertilize with a nitrogen fertilizer. But be careful: do not over-fertilize. Be sure to adhere to the indicated dosage.

Avoid waterlogging

In addition to a lack of nutrients, damage to the roots caused by excessive watering can also cause the leaves to turn yellow. To check, carefully dig up the roots and look at the condition of the roots. If they are mushy and putrid, you have found the cause of the yellow leaves.

Tip: Put compost or sand in the soil to improve the soil. This makes the soil more permeable.

Hydrangeas cope better with drought than with excessive amounts of water. The roots are able to store a lot of water. It is best to use special hydrangea soil.

ATTENTION: Avoid excessive watering!