Causes and characteristics of yellow leaves of orchids

Water yellow

Too much watering, basin soil water for a long time wet, resulting in a lack of oxygen in the soil, resulting in part of the fibrous root rot, thus weakening the ability to absorb water and fertilizer, causing tender leaves to become light yellow, flowers and leaves also gradually become dark yellow. After discovery, we should immediately control watering, stop fertilization, and often loosen the soil, so that the basin soil is well ventilated. If the disease is serious, it is necessary to remove the whole soil block from the basin and place it in the dry soil pile to make the water seep out quickly, and then plant it back into the basin after the drooping branches and leaves are restored.

Dry yellow

Too little watering, or long-term half-cut-off or missed watering, so that the water evaporation of the leaves is greater than the absorption, resulting in water supply falling short of demand, but also causing leaves to yellowing. The "dry yellow" gradually yellowed upward from the lower leaves, withered and scorched off, and when the petiole was serious, the petiole drooped and wilted. Immediately after the discovery, move the flowerpot to a cool place, spray some water on the leaf surface, and pour a small amount of water. Later, as the stems and leaves gradually return to straight and straight, and then gradually increase the amount of water, if too much water is suddenly poured at this time, it may cause cell wall separation, protoplast damage, and cause flower death.

Fat yellow

Excessive fertilization, especially too much nitrogen fertilizer and lack of phosphorus and potassium fertilizer, is easy to cause leaves to turn yellow, showing that the new leaves are thick, the leaves are mostly uneven, the old leaves gradually turn yellow and fall off, when the leaf tip is serious, even the whole leaf is scorched yellow. In this case, you should apply fertilizer immediately, increase the amount of water, let the fertilizer flow out of the drain hole, or pour the basin immediately, remove part of the old soil, wash the soil block with water, replace part of the new culture soil, and then plant the plant back into the basin.

Hungry yellow

The lack of fertilization, especially the lack of nitrogen nutrition in the soil for a long time, leads to thin and yellow leaves and branches, so it is necessary to pour the plant out in time, replace it with a larger pot, put it into a new loose and fertile culture soil, and replant it. After pouring water, put the seedlings in a semi-shady place to slow down the seedlings. After its growth resumes, thin liquid fertilizer or compound chemical fertilizer is applied.

Alkali yellow

When planting flowers that like acid soil in the north, such as camellia, orchids, Michelia, Mizi, sweet-scented osmanthus, because the soil in most areas of the north contains more salt and alkali, the above flowers and trees will gradually lose green and turn yellow due to the lack of soluble iron elements that can be absorbed by flowers after a period of time. At this time, 0.2% ferrous sulfate solution can be poured at intervals, while 0.1% potassium dihydrogen phosphate solution can be applied alternately to cure the "alkali yellow". At the same time, potassium dihydrogen phosphate also contains phosphorus and potassium elements, which is conducive to flower bud differentiation and improve flower quality.

Acid yellow

Southern China is red loam, the soil is acidic or slightly acidic, magnesium in the soil is easy to lose, leaves often show old leaves, leaf veins are first green and yellowing, can apply calcium magnesium phosphate fertilizer or spray 0.1% to 0.3% magnesium sulfate solution. For the improvement of acid soil, attention should be paid to the application of rotten organic fertilizer, lime and a small amount of lime, which can not only neutralize the acidity of soil, but also promote the decomposition of organic fertilizer.

Get a yellow tan

In summer, flowers that like semi-shade and are afraid of high temperature and heat, such as asparagus, hanging orchid, gentleman orchid, cyclamen, upside down hanging golden bell, etc., will be maintained in the place of strong light, which can easily cause tender leaf buds or leaf edge scorch or the whole leaf to turn yellow. immediately after it is found, it should be moved to a cool place with good ventilation for cultivation.

Yin jaundice

If the light-loving flowers are kept in the indoor light for a long time, the growth is weak, the leaves become thin and yellow, do not blossom or rarely bloom. To cultivate this kind of flowers, you usually need to put them outside in the sun or half-light, and then move them indoors to watch after flowering.

Dry yellow

In winter in the north, as a result of heating with heating or raw coal, the indoor air is dry, and some flowers that like moist air, such as orchids and tortoise bamboos, are prone to leaf tip drying or leaf edge scorching, scorch spots on leaves, edge curling and other phenomena, should often be sprayed and washed branches and leaves with warm water close to room temperature, and put a pot of clear water on the radiator or stove to increase indoor air humidity. For some precious flowers, it is best to use a plastic film mask at night and put a basin of water in the cover.

Cold yellow

The northern winter weather is cold, if the room temperature is lower than 8 ℃ at this time, some flowers that like high temperature, such as poinsettia, variable leaf wood, leaf flower, malachite bamboo tree, evergreen, etc., will suffer, causing leaves to yellowing and falling off; if the room temperature is less than 5 ℃, most flowers that like warmth and fear of cold will also suffer, leaves, flowers and fruits will be yellow, dry and easy to fall off. Therefore, after entering the room, the indoor temperature should be adjusted according to the temperature requirements of all kinds of flowers.

Disease and insect yellow

When flowers are infected by fungi, viruses and other pathogens, they will cause a variety of leaf spot diseases, resulting in local tissue necrosis of leaves, loss of green macula or yellow-green mottle, or yellowing and shedding of the whole leaf. Damaged by pests such as red spiders and shell insects, chlorophyll will also cause yellow and white spots on the leaves, or yellowing and shedding of the leaves. It is necessary to spray and control in time after discovery.

Poisonous yellow

The use of excessive pesticide concentration in the prevention and control of flower diseases and insect pests or spraying at noon in hot summer are easy to cause drug damage, causing leaf withering and yellowing; being polluted by toxic gases in the air or poisoned by toxic substances in the soil, it is also easy to cause local scorching of leaves or even death of the whole plant. Therefore, attention should be paid to the rational application of pesticides to eliminate air pollution and avoid soil toxicity.

Deficient yellow

Iron is one of the trace elements, you can choose and buy iron-containing trace elements in agricultural aid stores, spray foliar surface (some elements have poor mobility, spraying foliar surface can get quick effect) and base according to the instructions, long-term use of hard media, appropriate proportion of organic media, or supplement of organic fertilizer, the phenomenon of element deficiency can be improved or alleviated!

At the initial stage of iron deficiency, yellowing of new leaves will be caused, especially between veins. If it is not improved, it will cause local necrosis or albinism of tender leaves and die.

Magnesium deficiency caused yellowing, necrosis and reticulation between the veins of the leaves, but it was more obvious in the old leaves.

Sulfur deficiency resulted in dwarfing of plants, smaller leaves and overall yellowing, but it was also more obvious in old leaves. And this is described.

In addition, the branches and leaves that grow too luxuriantly are not pruned for a long time, resulting in insufficient light in the inner chamber, and it is also easy to cause the leaves to turn yellow and fall off. Attention should be paid to timely pruning to make it ventilated and transparent, and at the same time, attention should be paid to the appropriate application of phosphorus and potassium fertilizer to prevent branches from overgrowing.

Finally, it should be pointed out that the leaf yellowing of potted flowers is complicated, sometimes caused by one reason, sometimes caused by several reasons. Therefore, when it is found that the leaves turn yellow, it is necessary to carefully observe the right medicine to the case in order to achieve good results. At the same time, it should also be noted that not all yellow leaf phenomena are pathological diseases, for example, when "autumn wind sweeps the fallen leaves", deciduous flowers and trees wither; annual grasses and flowers wither and die; the aboveground branches and leaves of perennial flowers wither; flowers transplant due to temporary malnutrition, a small amount of yellow leaves fall off Individual flowers, such as Fusang, Magnolia and so on, are normal physiological phenomena and are not pathological diseases when their old leaves wither and yellow after sprouting new branches.