Yellow leaves on plants: what to do? | Common Causes

The causes of yellowing of the leaves can be very diverse, so you should check and rule out all possible causes one by one. It is also important that you examine the nature of the discoloration more closely. This identification is the first step in initiating the right measures. Look closely at young and older leaves and estimate whether the discoloration extends over the entire leaf surface, edges or leaf tips:

• yellow leaves with green leaf veins: general lack of nutrients or lack of iron
• completely yellow discolored leaf surfaces: waterlogging
• Yellowing of young leaves: iron deficiency
• occasional yellow spots on young leaves: pests
• yellow leaf edges on older leaves or cloud-like discolouration: magnesium deficiency
• Discoloration starting from the tip, first on older leaves, later on young leaves: nitrogen deficiency
• soft-leaved plants with yellow spots: irrigation water that is too cold

Room air that is too dry

In the cold season, yellowing occurs, starting at the tips of the leaves and spreading over the entire leaf. Some plants react to the drought with yellowish to brownish leaf edges. These phenomena indicate that the indoor air in the winter quarters is too dry. Most plants need a humidity level of 60 percent. If they stand on the windowsill so that their leaves are exposed to the warm air from the heating, they will dry out quickly. A bowl of water that you place on the heater can help. Some popular indoor plants attach great importance to high humidity and should therefore be sprayed daily:

• Schmalblättriger Nestfarn
• Wunderstrauch (Codiaeum variegatum)
• Dandelion (Aeschynanthus radicans)

waterlogging

Excessive watering causes the plant substrate to become waterlogged. If the roots are permanently in wet soil or directly in water, rotting processes can occur. As a result, the plant can no longer supply its leaves and shoots with enough water, which is why the leaves slowly turn yellow. To determine whether the plant has been watered, you should check the substrate with the finger test. If the potting soil feels fresh to moist, the water balance is right. If you notice a heavily waterlogged substrate, you should replace it immediately. Musty-smelling soil, mold on the substrate or standing water in the cachepot also indicate excessive watering.

Suboptimal location

Common causes of yellow leaves on ornamental plants are incorrect site conditions. Not all plants tolerate a place on the windowsill with a south-facing window, because direct sunlight quickly leads to excessive evaporation. Another consequence can be burns to the leaf tissue, which overheats severely in the sun. The affected leaf does not regenerate because the leaf tissue has already been severely damaged. The discoloration usually progresses to the base of the leaf and ends with the dried parts of the plant falling off. As a first remedial measure, an immediate change of location is recommended so that the plant can recover. Place the plant in a more shady spot and water the plant deeply.

pests

Many harmful insects suck the plant sap from the leaves, so that they appear blotchy when there is a heavy infestation. The unwanted tenants often settle on young leaves and soft plant parts when the plants have been weakened by over-fertilization. Harmful insects are clearly visible on closer inspection. To save the plant, you should adjust the care and immediately get rid of the pests by taking appropriate measures:

• Spray aphid colonies with baking soda
• Treat thrips with an aqueous solution of neem oil
• Wet scale insects with an alcohol-based soft soap solution
• Fight blood lice with an extract of oregano
• Nettle stock, garlic cloves or rhubarb leaves help against sucking plant pests

deficiency symptoms

Various yellow colors indicate that the plant is undersupplied. For healthy growth, every plant needs the main nutrients nitrogen, phosphorus and potassium as well as a number of trace elements and minerals. If these elements are missing, important metabolic processes are disrupted. The different clinical pictures come about because each nutrient is essential for certain functions:

• Iron is necessary for the production of chlorophyll
• Nitrogen as a central component of chlorophyll and proteins
• Magnesium is necessary for photosynthesis and an important building block of chlorophyll

nitrogen

Various causes lead to a nitrogen deficiency. If plants are supplied with organic material, they consume the nitrogen available to the plants in the first few weeks. They absorb the nutrient element in the form of nitrate or ammonium salts. If the decomposition processes continue, the microorganisms bind the nitrogen in the soil. The effects are only visible much later if the plants are not supplied with fresh material on a regular basis. If the crop suffers from a lack of nitrogen, growth is visibly disturbed. It develops thinner shoots and smaller leaves until leaf development finally stagnates. To correct the deficiency, you should give a mono-fertilizer or feed the plant with a diluted broth of brewed coffee grounds. A lack of nitrogen gradually announces itself:

• Plant forms larger leaves in the middle and upper part, which appear lighter than the rest
• Foliage in the lower area slowly turns light green
• sometimes stalks of young leaves appear purple or shoots develop purple streaks
• lower leaves turn increasingly yellow until they fall off

To demand

With an iron deficiency, the young foliage yellows evenly. If the deficiency is already very advanced, older leaves will also develop yellow discolouration between the veins. Plants are generally poor at absorbing iron from the soil. The pH value plays a crucial role here, which is why you should place plants with an iron deficiency in an acidic substrate. There is enough plant-available iron in this soil.

Magnesium

If a magnesium deficiency occurs, the chlorophyll-containing cell structures are broken down. The plant transports the stored magnesium to the young shoots and leaves. As a result, yellow spots appear between the leaf veins, which spread over the leaf like clouds. This deficiency is very common and has a variety of causes:

• Substrate is too wet, cold or acidic
• calcareous irrigation water or calcareous loamy soil
• Disturbed water balance or intensive stress on the plants

To eliminate the deficiency symptoms, you should provide outdoor plants with stale compost or well-ripened manure. Inorganic fertilization with a magnesium-sulphur fertilizer is recommended for indoor plants. Hydroponics can be supplied with Epsom salts.

over-fertilization

Houseplants are preferably supplied with mineral fertilizers, as these provide readily available nutrients and are more suitable for the limited space in the bucket. The disadvantage is that over time salts accumulate in the potting soil and on the edge of the pot. If the plant substrate is rarely replaced, there will be an excess of salts. With clay pots, the salt deposits can also show up on the outer surface, because the salt dissolved in the water diffuses through the porous material. The crystals attach themselves to the roots, burning the plant tissue and thereby preventing nutrient uptake. The leaves turn yellow. If you suspect a nutrient oversupply, proceed as follows:

• Immediately remove the plant from the used substrate
• Rinse the root ball under running water
• remove diseased and dead roots
• Thoroughly remove deposits from the flowerpot with a brush
• Plant in fresh substrate
• Water well and remove excess water