Why does thuja turn yellow and what to do to stop the process

Tui after winter turned a little yellow, especially towards the ends of branches. Growing for the third year, in a fairly high place. He fed nitrophos for the third year (this year) on a tablespoon per plant. Tell me what to do.

Andrew.

Specialist response

Hello Andrey!

There are many reasons why thuja turn yellow. Among them, one can distinguish seasonal changes in the color of needles, improper planting, lack of macro- and microelements, pests and fungal diseases, spring burning.

Change of color of needles depending on the season

Many conifers by winter change their color from green to brown-green, yellowish-green, brown. For example, the mountain pine Winter Gold, even with a slight fall in the average daily temperature, begins to change the color of the needles to golden yellow. And it stands all winter, as if bathed in the sun. If you come to the site in the spring, you may not recognize it, a completely different variety. In May, this pine is again green. Some varieties of thuja western can also surprise us with a change in color. For example, Aurescens has summer shoots of golden yellow color, and brown-yellow in winter. Europe Gold resembles the yellow form of the Smaragd thuja, in winter it becomes orange-yellow. But Yelloоw Ribbon - a fast-growing, valuable variety of thuja, has an intense orange-golden color and is ideal for creating contrast in the composition. Rheingold has a beautiful light golden yellow hue, but in the winter treacherously turns brown to brick.

In addition to natural seasonal changes, it must be remembered that the color of young growths always differs from old shoots. It just may be slightly lighter than the main mass of needles or differ in shade.

Landing errors

A common mistake of a novice gardener is an incorrect planting, namely, deepening a seedling. When planting, you need to follow the rule of the location of the root neck at the soil level: it should not be deep underground. With the plant in the landing pit, it is better to pull it up slightly. After two or three rains, the earth will settle, and the seedling will drop a little. Then its root neck will be located at the level of the soil.

With a sudden yellowing of the thuja, evaluate the landing site. Perhaps she is sitting in damp or is it a consequence of overdrying. The drying up of the root coma leads to the inevitable death of the seedling. If this is the case, rather water the plant and spray it, if possible, pritenit. In the future, regularly water, spray the crown with an anti-stress medicine such as Epin-Extra.

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Another violation of the water balance is stagnant waterlogging. When a lot of excess water accumulates in the root area, the roots rot and the plants begin to choke. If the slope of the site allows, then drainage grooves with a drain of water from the landing pits to the side of the slope will help.

When planning landings, you need to take care of the drainage of the site in advance. Proper water balance with optimal moisture content in the soil will keep your plantings healthy. If drainage is not possible, try planting plants on the so-called "raised ridges", i.e. small mounds of soil specially introduced for these purposes.

Nutrient deficiency

Macro- and microelements for plants are no less important than water balance. Lack of the following substances may cause yellowing of the shoots:

  • nitrogen,
  • potassium,
  • iron,
  • copper,
  • manganese.

Analyze the pattern of your seasonal top dressing; are all of the listed elements contained in the used fertilizers?

With a nitrogen deficiency, the leaves gradually become pale green, small, the branching of the shoots is suspended. A lack of potassium also disrupts nitrogen metabolism. Ammonia accumulates in the cells, causing yellowing and tissue death. When iron and copper are not enough, the process of photosynthesis and the formation of chlorophyll is disrupted, which just gives the green color of the needles. With a lack of manganese, plant leaves become yellowish due to intervein chlorosis.

Pests and diseases

A separate article can be devoted to the topic of pests and diseases, as well as fungal diseases. Yellowing of thuja shoots can be caused by pests such as thuja moth-motley, thuja aphid. If traces of pests or insects themselves are seen on plants, try spraying them with an insecticide.

Fungal diseases such as tracheomycosis wilt, shute can lead to the death of a seedling. The needles gradually turn yellow, turn gray, then become brown, and fall off. If the specimens are severely affected, they will have to get rid of them so that the spores of the fungus do not spread to neighboring ones. When individual shoots are infected, try to remove them, and spray the arborvitae themselves with a fungicide, and disinfect the soil under the plant. Repeat events several times during the season. But there is no absolute guarantee that the disease will not return in subsequent years.

Early spring spraying of the garden with Bordeaux liquid at the rate of 100 g of copper sulfate + 100 g of lime / 10 l of water can help to avoid problems associated with fungal diseases. If there are signs of the disease, systematic spraying should be used with an interval of 15-20 days. The flow rate of the working fluid is 15–25 l / 100 sq. m

Burning

When the thuja needles turn yellow after the winter, spring burn is most likely to manifest itself on them. This winter was generally extreme for many conifers. Heavy snowfalls, temperature changes, then early spring and late May frosts had a very negative effect on the appearance of green spaces. Sunburn is manifested by a gradual browning of the needles. At first, this is not entirely noticeable, as if the tops of the shoots are slightly dry and brightened. At this stage, it is difficult to understand what happened. But already in May it becomes clear whether it is a burn or not. If the shoots from yellowish became frankly brown, the seedlings were burnt. And this happens because the bright spring sun gradually revives the shoots, and the root system still does not work - the frozen, unheated soil in the root area does not allow the plant to receive life-giving moisture, its acute shortage appears and, as a result, burns.

Covering conifers with lutrasil, spandbond, burlap or other material does not give one hundred percent protection against burning. Sometimes it’s only worse - in places of tight fit of material to the crown conifers vypryvayut. It is much more effective to do prophylaxis - how to spill plants in the fall, making water-charging irrigation. It can also help activate the root system by watering already melted soil under plants with warm water (about 40 degrees).

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