Single yellow leaves on the nasturtium are normal. If increased discoloration of leaves, this is an alarm sign that the plant is not well. Simple measures bring back the color.
- a few yellow discolored leaves are a normal aging process
- check for possible causes only if there is an accumulation of yellow leaves
- too much or too little water can lead to yellow leaves
- overfertilization causes the leaves to turn yellow
- pests like aphids can lead to yellow leaves
Natural aging process
The nasturtium (Tropaeolum) is now available in different varieties as ground cover or climbing plant. It shows its yellow to orange flowers from about June until frost. During this time, the foliage should also be nice and green. Nevertheless, it can happen that it has individual yellow leaves. This is not yet an alarm sign, but part of the plant’s natural aging process. Older leaves die because it takes too much energy for the plant to maintain them. Also leaves that get too little light or are damaged, the plant separates from them and they turn yellow and eventually fall off.
Note: You can help the plant by removing leaves that start to turn yellow close to the stem. This way, the plant will have to invest less energy in this decomposition process.
There are many reasons why leaves turn yellow. The most common reason is water supply. Capuchin cresses react to both too much water and too little water with yellowish discoloration of the leaves. It is easy to determine if it is too much or too little water. If there is too much water, the leaves in the lower area are more likely to discolor first. The leaves in the lower area are also in greater danger of developing infections such as mold due to too much water.
If the yellow leaves result from lack of water, you can recognize this by the following characteristics:
- yellow leaves in the upper area (shoot tips)
- leaves hang down limply
- leaves partially curl up
You can easily prevent water shortage or waterlogging when planting. To do this, mix the soil with clay granules or expanded clay. This loosens the soil, but at the same time can store water very well, which is gradually released into the environment.
Too much fertilizer
Nasturtiums often reach impressive sizes, which is why many amateur gardeners assume that they have high nutrient requirements. It does need nutrients, and more than herbs usually do, but it is not a heavy grower. In terms of consumption, it is rather in the lower range of medium growers. Too much fertilizer, however, causes the leaves of the nasturtium to turn yellow and it sheds them.
If the yellow leaves result from overfertilization, proceed as follows:
- Stop fertilizing immediately
- water more frequently, but do not create waterlogging
- if possible, transplant to a location with less nutrients
Watering is a simple way to reduce the concentration of nutrients in the soil. However, you should pay attention to the right time here. The right time to water is late in the morning. At this time, the risk of waterlogging is also low, because the sun dries out the soil again during the day.
Tip: If the nasturtium is cultivated in a pot, simply change the substrate. Make sure you remove as much of the over-fertilized substrate as possible without hurting the roots too much.
However, you can not completely abandon nutrients, otherwise, again, yellow leaves may form due to undersupply. If you plant the nasturtium in the spring, mix a substrate with a medium concentration of nutrients. This consists of the following parts:
- 3 parts garden soil
- 2 parts compost (sieved)
- 1 part sand
Many are tempted to give the nasturtium additional care by giving liquid fertilizer. However, this should be largely avoided. Above all, do not use fertilizers that have a high nitrogen content. At most, you can still work in some compost around the plant during the season.
Although capuchin cresses are well protected from diseases and pests by their ingredients, they are still not completely spared. A common problem on these plants is aphids. They are usually particularly difficult to detect or are not found for a long time, since the large round leaves provide an optimal visual cover for the aphids.
The aphids injure the leaves with their mouth parts. The plant can still compensate for a few spots, but in the case of a heavy infestation, the leaves change color and are subsequently dropped. However, this is often a vicious cycle, then the aphids then crawl back onto the plant and continue to cause damage.
This you can easily combat:
- remove heavily infested leaves and dispose of in the residual waste
- Wash off aphids with a soft soap solution (1L water and 2 tablespoons curd soap)
- Encourage beneficial insects like ladybugs
- Strengthen the epidermis of the plant with Jauchen (field horsetail)
Tip: Look at the underside of the leaves occasionally. This will help you discover early if aphids have infested the plant.
Frequently asked questions
Doesn't liquid manure provide an additional supply of nitrogen?
Not every liquid manure has a high proportion of nitrogen. Field horsetail strengthens the plant’s epidermis, but has little nitrogen. As an alternative to liquid manure, you can also use broths or teas that contain little to no nitrogen.
How often should nasturtium plants be watered?
In the short term, nasturtiums do well with drought. During a prolonged dry spell, they should be watered thoroughly every three to five days.
Does harvesting encourage the formation of yellow leaves?
No, neither cutting off the flowers nor the leaves promotes yellowing. Only remnants of leaf and flower stalks turn yellow and fall off. Therefore, you should always remove leaves and flowers close to the main shoot.