Table of contents:
- The discoloration of the thuja in winter
- Over-fertilization and road salt
- Dried up thuja shoots
- Acidic soil damages thuja
- Diseases of leaves and shoots
- Thuja root rot
- Thuja and pests
Video: Measures against brown shoots in the thuja hedge
Your thuja suddenly has brown shoots or scaly leaves? Illness is not always to blame. Too much sun in summer or road salt in winter can also be responsible. Learn how to find out what is responsible for the brown discoloration of your thuja here.
The thuja, also called tree of life, is highly valued by us as a hedge plant. Although the thuja has no needles as a cypress plant, it belongs to the conifers. It has so-called scale leaves - small, close-fitting leaves. The tree of life as a hedge is a completely opaque, evergreen wall. It grows very quickly and is also hardy. Although the habitat is considered robust, it can also develop into a problem child: it develops brown scale leaves or simply dies. We explain the most common causes of brown shoots here.
The discoloration of the thuja in winter
Towards winter, trees of life change color to adapt to the extremely cold and dry weather, as with their ancestors in North America. So don't worry if your thuja hedge turns rusty brown. Thuja game species, such as the Western Tree of Life or the Giant Tree of Life, show up in a bronze-colored winter color. Cultivated forms discolour less or even keep their green color.
Over-fertilization and road salt
If your thuja hedge is close to the road, it can be damaged when using road salt. The thuja is sensitive to salt. A typical de-icing salt damage is the browning of the branch tips in the base area of the plant. Here the salt concentration is very high and the thuja is also hit by splashing water. In the event of damage caused by salt, it is best to cut the plant back thoroughly and then rinse it off. Through well-intentioned irrigation, the salt shifts to deeper layers of the soil. Browning can also occur if you have fertilized too much blue grain. This fertilizer also ensures that the salt content in the soil water increases.
Dried up thuja shoots
Timely identification of the disease is crucial for successful control.
Photo: iStock / Magdevski
Dryness is not a good thing for all Thuja species. Like other evergreen plants, they respond to the lack of water with a delay. The exact cause of the dried, yellow-brown shoots can then only be assumed. If you have kept your thuja hedge too dry, water it thoroughly. In addition, the soil should be carefully treated with bark mulch - this way you protect the hedge from drying out again. In summer it is possible that sporadic leaf burns occur when there is too much sun and too little water.
Acidic soil damages thuja
A too high manganese content in the soil causes brown-black needle discoloration. To save the acidic soil, first mix it with carbonated lime. About three months later you add mature compost and the soil has a balanced nutrient ratio again. Before you start liming, check the pH of the soil with a test set from the garden center.
Diseases of leaves and shoots
The thuja is more or less susceptible to various fungal diseases. The Pestalotia shoot extinction is probably the best known. The fungus Pestalotiopsis funerea is a weak parasite. The dying of the branches from the outside in is characteristic of him. Black-brown, pinhead-sized, round fruiting bodies form on the shoots. These then continue to produce spores of the fungus.
The Didymascella thujina mushroom triggers dandruff or needle tan. Mainly older leaf scales are affected by this disease. In the spring, round to oval, brown-black fruiting bodies appear on the affected scales. These also form further spores and thus infect other plants. The fungus spreads mainly in areas with high humidity and therefore occurs more frequently in the lower, shady part of the thuja. The kabatina shoot death is another common disease of the trees of life. This fungus usually hits the young, soft shoot tips and causes them to die. Plants on acidic soils are particularly sensitive to this disease.
Due to the timely detection and consistent control of the diseases, these do not usually pose any major dangers to the thuja. To do this, simply cut back the infected plants and treat them with suitable fungicides every two weeks. To prevent fungal infestation, it is best to ensure that the soil is rich in humus and loose when planted. A good water and nutrient supply is also important here.
In the event of damage caused by salt, it is best to cut the plant back carefully.
Photo: iStock / BasieB
Thuja root rot
The most dangerous disease for thuja is root rot. It destroys the entire bark tissue of the roots. Initially, the shoots turn yellow, then brown. In the end, the Thujas die completely. Young Thujas do not normally survive even one season with root rot. Even if only individual plants in the hedge are initially affected, the root rot can spread very quickly. Therefore, you should immediately remove infected plants from the hedge.
Here, too, the timely determination of the disease is crucial for successfully combating it. You can use fungicides to fight the fungus. However, you should replace the soil before replanting, as the fungal spores stay in the soil for a very long time and can in turn infect the new plant. You can prevent root rot by laying good soil for the thujas and taking good care of the hedge.
Thuja and pests
By eating the bark of young Thuja shoots, the black weevil ensures browning of the shoot tips. You can act against him with nematodes. The larvae of the Thuja leaf miner also lead to browning. It eats passages in the leaf scales. To get rid of the larvae, cut your hedge back often.
In contrast to the Thuja bark beetle, these insects do not normally cause any major damage. It can damage the bark of the tree of life so badly that it dies. Small holes in the trunk are a sure sign of this pest. Once the bark beetle has infested a thuja plant, the only thing left to do here is dig up, chop and dispose of it - preferably in winter, as you can also dispose of the hibernating beetle.
Photo: iStock / dropStock