Tree of heaven, Ailanthus altissima – plants and care

Garden lovers looking for a fast-growing tree will find what they are looking for in the Chinese tree of heaven with the botanical name Ailanthus altissima. This deciduous tree species grows up to 30 meters high in nutrient-rich locations. Even in lean and dry places, it still shoots up to 25 meters in height. It is not for nothing that the tree of heaven is considered the fastest-growing tree in Europe, because its seedlings are 2 to 3 meters high after just 1 year. For this reason, the Ailanthus altissima is regarded as an invasive plant in many countries because it crowds out native plants due to its competitive strength. Anyone who decides to cultivate the tree of heaven in their own garden should therefore prepare themselves from the start to keep its spread in check. Since it is poisonous in all parts,

Plant the tree of heaven properly

The magnificent ornamental tree with its large pinnate leaves and clusters of red fruit loves warmth and therefore prefers a sunny location. The tree of heaven does not make any special demands on the soil quality and also thrives in dry, nutrient-poor soil. In principle, you can plant the tree all year round, just not during a frosty period. However, since its leaves do not sprout until late, there is a risk that the young shoots will freeze to death if there is insufficient winter protection when planting in late autumn. It is therefore advisable to plant the young tree in the spring, when the frost has pulled out of the ground.

With regard to the choice of its location, the distances to the neighbors, to the street and to your own house must be taken into account. The minimum distance from the tree of heaven to the street and to the neighboring property is regulated by law in Germany, at state level. In order to avoid any trouble here, the garden enthusiast informs himself in good time at the responsible authorities. The distance to your own building ideally corresponds to the expected height of the tree, in this case 25 meters.

Selection, purchase and transport

Tree nurseries usually offer the tree of heaven either in containers or as bales. The following criteria should be considered when making the selection:

• Smaller trees get used to the new location faster.
• Smaller initial size is compensated by stronger growth.
• Trunk and branches are unharmed.
• Remove any jute bandages to check.
• Stronger roots must not curl up in the container.
• A radiating root system is ideal.
• Protect against any injury or crushing during transport.
• Attachment ropes provided with padding.

If the transport time is longer, the root ball is kept permanently moist. This also applies if the young tree is not planted immediately but is stored for a while.

Soil preparation and planting

At the selected location of the tree of heaven, the experienced gardener proceeds in the following steps:

1. The young tree is placed in a vessel with water until no more air bubbles rise.
2. A planting hole is dug that is at least twice as large as the root ball. The excavation is mixed with part garden compost and a few handfuls of horn shavings. Barn manure is unsuitable because it could damage the young roots.
3. The bottom of the planting hole is loosened up with a rake. If there is a risk of waterlogging at this point, first lay a 5 cm high drainage made of gravel, lava granules or broken pottery.
4. The hobby gardener spreads a layer of the topsoil-compost mixture over the drainage.
5. The root ball is freed from any covering. This applies not only to the plastic container, but also to a bale of cloth, even if it is a material that will decompose. Experts report that decomposition often takes much longer than expected, which hampers root development.
6. The small tree of heaven is positioned in the middle of the planting hole and buried with the potting soil. It must never sink deeper into the ground than during cultivation. If the base of the trunk sinks into the ground, the fine roots suffer considerably from this circumstance and do not receive enough oxygen, which considerably impairs the water supply of the entire tree. Experienced hobby gardeners take into account that the loosely heaped substrate will continue to settle after watering, even if you have trampled it down beforehand.
7. Three support posts are driven into the ground around the young tree and connected to it with wide straps. Under no circumstances should wire be used for this, because such binding material would constrict the trunk. The swaying of the tree trunk should be contained but not completely prevented.
8. Finally, the Ailanthus altissima is poured generously, whereby a pouring rim with a slight slope towards the middle is helpful. A layer of bark mulch protects the young roots from moisture loss.

The support stakes remain on the tree for at least the first two years and can then be removed.

maintenance

The tree of heaven is a remarkably frugal plant that does not require much care:

• Water regularly for the first two years.
• Work some compost into the soil once a year.
• Protect from intense sunlight during the growth stage.
• To do this, wrap the trunk with mats made of bamboo.
• Check the connection to the posts from time to time.
• Do not allow binding material to grow in.
• Winter protection required for the first three years.
• Adult tree of heaven is frost-resistant down to -20° Celsius.
• Also protect against strong radiation in winter.

The bark of a young tree of heaven must be protected from strong sunlight because otherwise it will burst open, which opens the door to infestation with fungi and pests.

propagation

For a tree, the growth rate of the tree of heaven is really breathtaking. Its natural propagation takes place correspondingly quickly through root runners, from which rapidly growing shoots arise. In addition, each tree produces vast amounts of winged seeds that can travel great distances. Anyone who already has a specimen in the garden and would like to plant it elsewhere will therefore prefer vegetative propagation.

To do this, a strong shoot that has at least 3 to 4 leaves is cut off the tree with a sharp knife. Put it in a glass with water or in a pot with nutrient-poor potting soil until it roots. Given the speed at which the Tree of Heaven grows, it doesn’t take long for strong roots to form. Then the cutting can be planted in the ground at its new location. If it gets a regular dose of water there and good protection from frost and intense sun rays, a new sapling will develop within a short time.

To cut

The tree of heaven does not require a special cut. It is sufficient if the tree is thinned out in spring:

• Cut off dead, damaged and withered shoots.
• Make the cut right at the roots, without leaving a stub.
• Be careful not to injure Astring.
• Cut off crossing branches.
• Completely remove branches growing inwards.

If you don’t like the growth form, you can shorten the shoots accordingly. The knife is applied just above a bud.

control spread

Despite its aesthetic appearance, its high ornamental value due to the beautiful foliage color in autumn and the decorative red fruit clusters that remain on the tree in winter, the tree of heaven is fought in numerous countries around the world as an invasive plant and is on the ‘black list’.

Professional root barrier

The reason for the classification of the tree of heaven as invasive is its aggressive spread through root suckers and self-seeding. Experienced hobby gardeners respect this fact when planting and invest in a professional root barrier. This is a particularly stable geotextile that also withstands the strong urge to spread from the roots of the tree of heaven. It is waterproof and absolutely frost-proof. This anti-root shield is placed vertically around the root system like a ring and securely closed with a click bar. The Ailanthus altissima has no chance of spreading its runners underground uncontrollably, from which the unwanted shoots grow. However, care should be taken to

Remove seeds and shoots in good time

Since the mature, winged seeds are blown by the wind, dispersal is kept in check by timely removal of the infructescence in the fall. In this way the tree is robbed of its beautiful winter decorations; however, combating young trees that have already settled in undesirable places is so time-consuming that most gardeners remove the fruit. In addition, shoots are immediately removed from the soil in places in the garden where they do not belong. A disposal of the plant material on the compost should be avoided. It is more effective if all components are burned.

Sawing off alone is not enough

Gardeners who want to get rid of a tree of heaven enter into what can sometimes be a long struggle. Simply sawing off the trunk doesn’t bother the tree much, because in this case it happily continues to sprout from its up to 15 m long foothills, also known as bud shoots. The only way to permanently get rid of the Tree of Heaven is to tire it out. This is done by immediately pulling out each new shoot. Over time, the vitality of the tree slacks and it stops forming further shoots.

At this point, the toxicity of the tree of heaven should be pointed out again and the need to wear gloves and eye protection for all work.

diseases and pests

As a member of the bitter ash family of plants and due to its toxic components, the tree of heaven is largely resistant to diseases and pests. Only gray mold can cause problems for him. This fungal infection leads to shoot death and kills off young, non-lignified tissue. As a preventive measure, too dense planting distances should be avoided. Chemical pesticides are not permitted for use in private gardens. Among the pests, one moth has specialized in the tree of heaven as food and is therefore also known as the Ailanthus moth. Originally produced for silk production in China, it damages ornamental trees in Europe. Combat measures have not yet been developed because the tree of heaven itself is now increasingly being combated.

risk of confusion

A young tree of heaven in particular is easily confused with the vinegar tree, which has similar pinnate leaves, but they are significantly smaller. The vinegar tree is also listed as an invasive plant on the ‘Black List’ so that a mix-up has no significant consequences. At first glance, the decorative Asian tree ‘Schmuckblatt Mahonie’ is also mistaken for a young Ailanthus altissima. Not only because of the pinnate leaves, but also because of the similarly yellow inflorescence. However, it is most frequently confused with the ash, whose leaves are pinnate in pairs and the buds are black. Due to the similarity with the common ash, the tree of heaven is also popularly known as ‘stinky ash’ because its flowers in June and July give off an unpleasant scent.

Conclusion
It is beautiful to look at with its large, green, pinnate leaves. Its colorful foliage and the reddish-brown clusters of fruit adorn the dreary garden in autumn and winter. However, it spreads so aggressively that the tree of heaven now appears in the top 100 of the ‘black list’ of invasive plants. However, if you take this into account when planting and use a stable root barrier, you can keep the rapid growth under control.