Thuja, the tree of life, is actually not native to Germany. The beautiful trees occur in three species in eastern Asia, and two others come from North America. Thuja is poisonous to humans, but is used in homeopathy. The trees are popular as hedge plants because they are green all year round and grow very densely.
Planting
The tree of life is available in stores in very different sizes. Thuja grows quite quickly and is relatively resilient, so you can easily buy the small, inexpensive plants. They grow even better than larger specimens. However, older trees can also be transplanted quite easily. The soil in the planting hole should be heavily mixed with compost, a large planting hole is required, and the root ball must be well watered. If thuja is planted as a hedge, the distance between the individual plants should be around 40 to 50 cm. After planting, water well. Only when height growth begins again, i.e. the tree is rooted, can you water a little less. Brown tips indicate dryness!
Soil and location
Thuja needs a planting substrate or soil that holds water well, because the plants love moisture. Despite all the love for wet feet and high water consumption, at least in the first three years of life, the soil still needs to be loose and permeable. The nutrient content of the soil is not that important; it can be neutral, acidic or calcareous. The trees actually prefer the latter. If the soil is too acidic, the needles of the arborvitae turn black, which is due to the high amounts of manganese they contain. You can get rid of this after about two to three months with a little carbonic lime and compost. The location does not have to be in full sun, but arborvitae generally want a lot of light, so intense sunshine is definitely better for the plants than shade. Shady locations mean that the arborvitae does not grow as densely, evenly and compactly and therefore does not offer good privacy protection - Thuja suffers from a lack of light.
Fertilizing and watering, cutting
Thujen need starting fertilization and annual fertilization. The starting fertilizer depends on how the tree is purchased: The starting fertilizer is usually contained in the plant ball, but not in the bare roots. Seasoned manure, horn shavings and rock dust are very suitable for fertilizing when planting. Conifer fertilizer is suitable for annual fertilization. What is more important is that the plants always have enough water available. Thuja's water balance is regulated quite well if mulched regularly, as this allows the soil to hold water better. If the tree of life is not watered enough, the needles will quickly turn brown! In its natural habitat, the tree of life grows at the edge of water and in swampy areas.
Thuja is cut in spring, around February or March. If individual shoots stick out in summer, they can still be carefully cut. However, for bird protection reasons alone, this should never be done with electric hedge trimmers, but should always be done by hand. Since Thuja is poisonous, we recommend that you wear gloves. Thuja should only be cut in the young shoots, because old wood does not sprout again (this is not a disease, but normal).
Pests and diseases
Thuja is actually not very susceptible, but can quickly develop brown tips in dry conditions. The plants also show fungal infections with brown shoots and dark discoloration. The only thing that helps is a proper pruning; if necessary, fungicides can also be used. A distinction is made between Pestalotia shoot dieback (the branches are infected first, conspicuous black fruiting bodies with numerous spores form on the branches), needle or scale brown (this usually affects older shoots, the infection tends to spread), Kabatina - Shoot dieback (young and soft shoot tips die) and thuja root rot. The latter is also a fungus that causes yellow discoloration of the needles and spreads incredibly quickly. The needles eventually turn brown and the entire plant dies.
Before a new thuja can be planted, the soil must be replaced over a large area. The fungus is not only located in the roots, but also lives in the soil around the plant. The strong tendency to fungal infections is typical for plants that like it moist - because fungi also need very moist soil. It is therefore important that the tree of life sits in loose soil that retains moisture but is still well ventilated. Other pests actually don't bother the tree of life, insects are actually not a problem.
My personal tip: distance
Thuja is beautiful as a hedge, but the poisonous plants can cause skin irritation on contact. Anyone who plants Thuja as a property boundary should keep a certain distance from the sidewalk and the street in order to protect passers-by and not to endanger children in particular. There is another reason to leave a little more space to the road: Thuja is sensitive to road s alt. The shoots near the ground turn brownish-black when the plant comes into contact with the s alt. That doesn't look nice, and cutting it back is not a solution, because then the privacy protection will not be permanent, at least in the lower area.
Tips for speed readers
- Be sure to wear gloves when cutting, as thuja is poisonous and can cause skin irritation if touched.
- Until the trees are rooted and grow tall again, they must be watered extensively and repeatedly.
- The tree of life needs planting substrate that is loose and still retains moisture well.
- Sunny to partially shaded, but always bright locations are suitable for Thuja.
- When planting, fertilize with a mixture of manure, horn shavings and rock dust.
- Compost and mulch can be used for annual fertilization, conifer fertilizer is also suitable.
- The tree of life must always have plenty of water available - mulched soils hold water better.
- Thuja is cut in February or March because the tree then grows well and sprouts beautifully. Individual shoots can still be trimmed in summer.
- Thuja likes to catch fungal infections, which in mild cases can be controlled by pruning; in severe cases a fungicide helps.
- Root rot leads to the death of the plant - before a new tree of life is planted, the soil must be replaced over a large area.
What you should know about Thuja diseases and pests in brief
Thuja leaf miner – diseases
The thuja moth caterpillars particularly like to eat the fresh shoot tips of the plant. In order to prevent the voracious caterpillars from spreading, the hedge must be trimmed regularly from February or March. The clippings must be disposed of outside the garden, otherwise the animals can spread further. The infestation can be recognized by brown-colored shoots that become dry. In June the moths begin to fly and spread very quickly. You definitely have to cut back the hedge first. If there is a severe infestation, you should use approved agents to combat it at the beginning of July (egg-laying time).
Thuja bark beetle
This beetle usually only attacks weak and sick plants. Dying branches have small thickenings at the base. The approximately 3 mm large, black, rounded beetle sits there. They often occur after extremely dry years. You can prevent it by taking good care of your plants. Cutting back the branches is usually enough to eliminate the beetles. Do not dispose of the branches in the compost!
Kabatina thujae
The mushroom can be recognized by initially small black dots on the shoots. The disease can be easily recognized in May, when the spores break open. The fungus can be contained by heavily pruning the tree. Thuja occidentalis and Thuja plicata are particularly affected by this fungus. Proper care of the thuja includes providing the plants with sufficient lime and magnesium. A lack of supply promotes fungal infestation, as does waterlogging.
Didymascella
Brown scales on the thuja shoots from January or February indicate this fungus. At first there are just a few brown flakes. There will be more and more of them until black spore deposits can be seen in May. The entire shoot dies. A timely pruning in spring removes sources of infection and the disease does not even break out. Thuja occidetalis and Thuja plicata are particularly susceptible.
Drought damage
Thuja plants react to a lack of water with brown and dying branches. If the entire plant is not affected, new side shoots will form. The thuja needs sufficient moisture all year round, not just when it is sunny and warm.
S alt damage
S alt damage often occurs on plants that are right next to a road. They get hit by road s alt in the winter. Stunted growth, growth depression and even death of the plant can occur. These plants should not be over-fertilized as this can contribute to additional s alt contamination. S alt accumulation in the soil should be prevented (wind protection fence, similar to that on tennis courts).
