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The thuja is still one of the most popular plants when it comes to creating a closed hedge. Although the thuja is also called the tree of life in German, it happens again and again that the plant unexpectedly and surprisingly turns brown. The possible causes behind this and the measures that promise a remedy are explained below.
Reasons for a brown thuja hedge and ways to remedy it
Why a tree of life turns brown can have different reasons. The most common causes are these and the following, briefly explained measures can be easily remedied:
The wintry brown color
The wild species of thuja in particular regularly change color from the well-known, rich green to brown and rust tones in winter. This discoloration is not a "fault" or a cause for concern, but is used by the plant to adapt to the extremely cold and dry winters of its native North America. Cultivated forms, on the other hand, are less brown in winter. Varieties such as "Smaragd", on the other hand, usually get through the cold season without any discoloration.
A remedy is neither possible nor necessary.
If the hedge begins to discolour at the tips of the branches close to the ground, road salt can be the cause. This gets, for example, from traffic areas running next to the hedge with the melted ice or snow into the ground, or sprayed directly onto the branches. The salt used to combat black ice leads to an excessive salt concentration in the soil and plants. Too much salt dehydrates the thuja so that the branches are damaged from the point of entry into the plant, i.e. from the roots.
- cut off affected branches
- Rinse plant to wash off salt
- Water the soil well to dilute the salt
The tree of life is damaged by over-fertilization in the same way as with road salt. In addition to other nutrients, blue grain in particular provides salts which, in excessive concentrations, can be dehydrating and cause considerable damage.
- remove brown shoots
- Collect any blue grain that has not yet dissolved
- Water the soil well to dilute the salts
In general, the Thuja is considered to be very susceptible to drought. However, the symptoms in the form of brown discolouration only appear with a considerable time lag, so that it is quite difficult to assign the cause if there is a lack of moisture. The lack of sufficient water comes into question above all when the soil is perceived as very dry on the one hand, but other causes also rule out.
- Water the soil thoroughly
- Apply bark mulch or similar to reduce soil drying out
The brown-black discolouration of the needles caused by acidic soil is mainly due to an oversupply of free manganese in the soil. More generally, the imbalance in the supply of nutrients caused by overacidification can be cited.
- Deacidification by adding carbonate of lime to the soil
- after deacidification, a balanced supply of nutrients is produced, for example through compost
Like all other plants, there are various diseases to which the tree of life is particularly susceptible. This includes, above all, the fungus Pestalotiopsis Funerea, which causes the so-called Pestalotia dieback. Shoots attacked by the fungus turn brown and die off completely after sufficient damage. Other diseases are, for example, also caused by a fungus Needle and dandruff tan.
Far more dangerous is the so-called Thuja root rot, which not only damages individual shoots but also the entire plant starting from the root and causes it to brown. Here, too, the cause can be found in a fungus, namely the Phytophthora cinnamomi.
- Cut back affected shoots or plant parts completely
- Control with suitable fungicides or sprays adapted to the pathogen
Other causes of brown spots, especially brown shoot tips, are insects. the vine weevil for example, the bark of the young shoots pierces and irreparably damages them until they turn brown and die. It is the same with the leaf miner, which - as its name suggests - bores tunnels into the plant and thus promotes discoloration by damaging the water-carrying pathways.
- Cut off and discard affected shoots
- use pesticides if necessary, but mostly unnecessary in the case of normal infestation and early detection and removal of the infested shoots
Prevent instead of fighting
Tips so that the tree of life does not turn brown in the first place
If the thuja hedge turns brown, the causes can usually be found out quite quickly with a little search and thought. With the countermeasures mentioned, at least the loss of entire plants can then also be avoided. However, it would be even better to take precautions from the outset so that no brown discoloration occurs in the first place. This is not possible for all causes, because fungal and insect infestation in particular can hardly be prevented. However, even with these causes, the resistance of the plants can be strengthened through good care and supply with water and nutrients. As a result, they can cope far better with external attacks and can often even deal with them on their own. According to the motto "help for self-help", a good and balanced supply of the thuja plants is the be-all and end-all of strong and resilient organisms that can make ends meet without the unwanted brown discoloration.