What if my plants turn yellow

Yellow leaves on plants: what to do | Common causes

It is normal for a plant to get yellow leaves. After the maximum life expectancy of a leaf has been reached, the plant stops supplying nutrients and water. The leaves dry up and fall off. Irregular discoloration on the leaves, however, indicates suboptimal conditions, diseases or pests. The action you should take depends on the cause.

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Recognize patterns

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

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

Indoor air that is too dry

In the cold season of the year there is an increasing number of yellow discolorations that begin at the leaf tips and spread over the entire leaf. Some plants react to the drought with yellowish to brownish discolored leaf margins. These phenomena indicate that the indoor air in the winter quarters is too dry. Most plants need a humidity of 60 percent. If they stand on the windowsill so that their leaves are exposed to the warm air from the heater, they dry out quickly. This can be remedied by placing a bowl of water on the heater. Some popular houseplants attach great importance to high humidity and should therefore be sprayed daily:

  • Narrow-leaved nest fern (Asplenium antiquum)
  • Wonder shrub (Codiaeum variegatum)
  • Pubic flower (Aeschynanthus radicans)
Note: Green lilies often tend to have yellow and brown leaf tips in winter. These often arise at a location on the windowsill directly above the heater.

Waterlogging

Excessive watering leads to the plant substrate becoming wet. If the roots are permanently in wet soil or directly in the water, putrefaction processes can occur. As a result, the plant can no longer supply its leaves and shoots with sufficient water, which is why the leaves slowly turn yellow. To determine whether the plant has been doused, you should check the substrate with a finger test. If the potting soil feels fresh to moist, the water balance is right. If you notice a heavily wetted substrate, you should replace it immediately. Moldy smelling earth, mold on the substrate or stagnant 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 of the leaf tissue, which overheats 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 when the dried up parts of the plant fall off. As a first aid measure, it is advisable to change location immediately so that the plant can recover. Move the plant to a more shady spot and water the plant penetratingly.

Pests

Many insect pests suck the sap from the leaves, so that they appear spotty when there is a strong infestation. Often the unwanted tenants settle on young leaves and soft parts of plants when the plants have been weakened by over-thinning. Insect pests are clearly visible on closer inspection. To save the plant, you should adjust its care and immediately get rid of the pests by taking appropriate measures:

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

Deficiency symptoms

Different 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 arise 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 component of chlorophyll
Note: Yellowing of the leaves caused by a lack of nutrients is known as chlorosis. This bleaching is a disease that manifests itself in a lack of chlorophyll and can look different.

nitrogen

Various causes lead to a nitrogen deficiency. If plants are supplied with organic material, they consume the plant-available nitrogen 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 regularly supplied with fresh material. If the crop suffers from a lack of nitrogen, the growth is visibly disturbed. It develops thinner shoots and smaller leaves until leaf development eventually stagnates. To remedy the deficiency, you should give a mono-fertilizer or provide the plant with a diluted broth made from brewed coffee grounds. A shortage of nitrogen is gradually becoming apparent:

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

iron

If there is an iron deficiency, the young leaves will yellow evenly. If the deficiency is already very advanced, older leaves develop yellow discoloration between the veins. In general, plants cannot absorb iron from the earth. The pH value plays a decisive role, which is why you should place crops with an iron deficiency in an acidic substrate. There is enough plant-available iron in this soil.

magnesium

If there is a magnesium deficiency, the chlorophyll-containing cell structures are broken down. The plant transports the stored magnesium into the young shoots and leaves. As a result, yellow spots appear between the leaf veins, which stretch over the leaf like a cloud. This deficiency symptom is very common and can be traced back to different causes:

  • Substrate is too wet, cold or acidic
  • calcareous irrigation water or calcareous clay soil
  • disturbed water balance or intensive stress on plants

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

Overfertilization

Indoor plants are preferably supplied with mineral fertilizers, as these provide nutrients that are readily available and are better suited for the limited space in the tub. The disadvantage is that, over time, salts build up 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 to the roots, burn the plant tissue and thereby prevent nutrient absorption. The leaves turn yellow. If you suspect a nutrient oversupply, do the following:

  • Remove the plant immediately from the used substrate
  • Wash out the root ball under running water
  • Remove sick and dead roots
  • Thoroughly remove deposits from the flower pot with a brush
  • Plant the plant in fresh substrate
  • Pour well and remove excess water