Nitrogen deficiency
If there is a lack of nitrogen, the entire leaf usually turns yellow. Initially, only the older leaves in the lower area of the hydrangea are affected, only later does the following leaves discolor. As a result, the flowers can also wither.
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remedy
Fertilize the hydrangea with a nitrogen fertilizer from the gardening trade. Please note the dosage indicated on the package and do not over-fertilize the hydrangea. Too much nitrogen can also damage plants.
Chlorosis
Iron deficiency usually occurs in connection with the acidic soils preferred by the Hydrangea. The younger to middle-aged leaves are affected first. They show a yellow-green to lemon-yellow discoloration. The leaf veins are sharply demarcated and dark green.
If the iron deficiency persists, the following damage appears:
- All of the foliage turns yellow.
- Brown necroses develop from the leaf margin.
- The stems become thinner.
- The roots shorten and show an unhealthy brown color.
remedy
Always fertilize the hydrangea with a special iron-containing fertilizer. If an iron deficiency still shows up, you can use a pure iron fertilizer.
Caution
Iron fertilizer is toxic, which is why you should definitely wear protective clothing when spreading it.
Soil pH
In order for red hydrangeas to keep their bright flower color, the soil must have a relatively high pH value. This can mean that the plant can no longer absorb sufficient amounts of iron. If yellow leaves appear on a red hydrangea, you should therefore correct the pH value. Organic fertilizers such as compost are well suited.
Tips & Tricks
Foliage that turns yellow in autumn is normal due to the natural vegetation cycle. The hydrangea is one of the deciduous plants in which the leaves initially turn yellow in autumn and then fall off by themselves.
