Tips & Tricks

Tree of heaven - How to keep the spread under control

The tree of heaven is beautiful to look at, but it spreads quickly and uncontrollably. If you want to stop the spread, be patient.

The tree of heaven brings many advantages to the hobby gardener. The bitter ash plants from Asia place few demands on their location or the substrate. The tree of heaven grows quickly, has attractive fragrant flowers and offers an atmospheric autumn color. However, it should not go unmentioned - the tree of heaven is a refugee from the garden. It not only grows quickly, it also spreads uncontrollably and literally takes the air to breathe from other domestic plants.

Tree of heaven is spreading rapidly

The seeds of the tree of heaven grow almost everywhere and if you look carefully for the trees, you will often find them between sidewalk slabs and cracks in the wall. Even if the god trees with their yellow-green flowers and red tufts of fruit offer an attractive sight, they are invasive plants that are among the top 100 on the “black list”. Trees are spreading rapidly, especially in cities, and are often replacing conventional street trees.

Tip: Young trees are only hardy to a limited extent. Another consolation, city trees tolerably have a life expectancy of 50 years.

If you are thinking of planting a tree of heaven, you should be aware that your tree will tower over it within a few months and grow up to 20 meters high. The allotment garden is therefore not the right place for the impressive plants. There should be enough space to give the tree a unique position. The ideal location is about 20 meters from buildings and walls.

Measures against the spread of the tree of heaven

  1. Create a root barrier
  2. Remove seeds and shoots
  3. Sawing off the tree

If you plant a young tree of heaven, you give the go-ahead for intensive growth. This is not only evident from the fact that the trees don't need three months to grow one meter high, there is also a lot going on hidden from our eyes. The roots form a sprawling network just below the ground and have a destructive effect on the neighboring plants.

❶ The most effective solution: creating a root lock

A professional root barrier is a worthwhile investment and, in the long term, the most effective way to counter the spread of the tree of heaven. A root barrier consists of a particularly stable material. This special geotextile does not let air or water through and withstands even the strongest frosts. Attach the root barrier in a ring around the roots of the tree of heaven. The easiest way to do this is during planting.

Note: Root locks can also be used subsequently. However, this is much more labor intensive since the roots first have to be excavated.

The geotextile is brought into the ground at an appropriate distance from the root ball and closed with a click bar.

Use a root barrier - step by step

  1. Dig out the planting hole
  2. Insert the plant
  3. Adjust root lock
  1. Close root barrier
  2. Fill in the substrate
  3. Close the planting hole

If you are planting a young tree, the planting hole should be dug out in an appropriate size. So that the plant can develop at all, you should give the roots some leeway. Do not set the root barrier too tight and allow about three times the distance of the root ball. Otherwise a stable root network cannot be formed. If the roots are constricted in this way, the plant cannot spread and atrophy.

❷ Courageous intervention - the removal of the seeds and shoots

The seeds of the tree of heaven are carried away by the wind and germinate at almost every new location. To prevent this, you should take heart and remove the fruit clusters in autumn. Then the plant will appear less attractive in winter, and you won't have to dig out tons of young trees from the ground in the following year. If it has already sprouted, you should consistently remove all undesirable shoots from the ground. As the plants grow, it becomes increasingly difficult to dig up the trees.

Tip: The removed plants and parts of plants should not be stored on the compost. To consistently prevent the tree from spreading, burn the removed shoots.

❸ If nothing helps - saw off the tree of heaven

Anyone who was not aware of the joy of growth of the tree of heaven will soon no longer be able to speak well of the bitter ash family. The trees have grown too big and have successfully displaced planting neighbors? The only solution seems to be simply sawing the tree off. This seems logical at first, but will prove to be less effective in practice.

If you sawed off the trunk of the tree of heaven, the spreading of the plants is only apparently helped. If no root barrier has been created, the roots spread almost freely within a radius of up to 15 meters. Even when the tree is felled, no bar is put forward. If you only saw off the trunk, you will notice that all the more new shoots appear in the area mentioned. If you do not have the option of completely removing the root, you can try to “tire” the tree. To do this, all new shoots are removed as quickly as possible. It will take some time before the tree gradually lacks its growth instinct and stops completely as a result.

The methods of controlled spread with their advantages and disadvantages

Remove seeds and shootsThe method proves to be complex.
If the seeds are not removed in time, they will be carried away by the wind.
Create root barrierThe root barrier should already be created when planting.
Use a product from the specialist trade that seems really stable enough.
Do not set the root barrier too tight, otherwise no plant will be able to develop.
Saw off the treeSawing off the stem will not prevent the plant from spreading.
The roots continue to push new shoots eagerly.
Only if these shoots are consistently removed will this tire the tree and it will gradually stop growing - also at the roots.
Caution: The tree of heaven is poisonous in all parts of the plant. Gloves and eye protection should always be worn during felling or disposal work.