Trees, shrubs and hedges form enormous root networks underground. If you don’t think about this and don’t apply a root barrier, you can have a rude awakening in a few years. The problem often only becomes apparent after planting, when the runners poke holes in pond liners, lift flagstones, or penetrate drains and other crops. It can be particularly problematic when the foothills appear in the neighbor’s garden.
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To prevent this, the trade offers special foils in different strengths and widths. The thickness of the required rhizome barrier depends on the growth behavior of the respective plants.
The term root barrier is usually associated with bamboo. But other plants such as reeds, raspberries or sea buckthorn also need a corresponding barrier. A rhizome barrier can also be installed later, but this is usually relatively difficult and, above all, very complex and labor-intensive.
Root barrier for different types of bamboo
Especially with bamboo or with most species, the installation of a rhizome barrier is essential. As a rule, it makes the most sense to bring them in at the time of planting. Whether a subsequent installation of a root barrier is recommended can be seen from the growth form of the bamboo species in question.
On the one hand there is the strength of the blades. If these have a diameter of more than 3 cm or if stalks are already growing more than 30 cm away from the actual mother plant, it definitely makes sense to install a root barrier afterwards.
A rhizome barrier is also required if the bamboo grows higher than 4 m or its leaves are wider than 5 cm. For the species ‘Fargesia’ and ‘Borinda’ no such barrier is usually necessary. It makes the most sense to seek advice on the need for a root barrier before purchasing bamboo plants.
Noteworthy when installing
A root barrier especially for bamboo must have a certain thickness so that the root suckers cannot penetrate it. A conventional pond liner, for example, is not particularly suitable for bamboo. The barrier should be at least 2 mm thick and at least 70 cm wide and deep. Depending on the type of bamboo, a depth of 100 cm may also be advisable.
For installation, a correspondingly large area must first be marked out. The respective space requirement depends on the bamboo species, but should not be less than 8 – 12 m². Now the staked out area is excavated or dredged to a depth of 65 cm, depending on the equipment available.
After excavation, the root barrier is placed in the hole all the way around and with a slight outward incline so that about 3-5 cm of the foil protrudes from the hole. This overhang is important because the roots would otherwise grow beyond the foil and thus be able to spread unhindered despite the barrier. Roots that then still protrude over the foil can be easily cut off. Furthermore, it is important to ensure that no stones get between the root barrier and the soil that could damage the barrier.
The ends of the foil should not overlap if possible. They are connected or screwed to an aluminum locking rail. Instead of a sealing bar, the ends of the film can also be sealed, for example with a hot air gun or a film sealer. It is important to ensure that the ends of the film are connected without gaps, because the strong roots of the bamboo will squeeze through even the smallest gap. Once the root barrier has been inserted and welded, the earth can be filled up again and the bamboo planted. Finally, you should water the bamboo thoroughly.
Install rhizome barrier for Chinese reed
Opinions differ on the need for a root barrier for Chinese reed. Although this plant does not form any runners, the roots can still spread relatively strongly. If the Chinese reed is to be near a pond or a well-kept lawn, it makes sense to attach a corresponding root barrier. Especially since this plant can also cause damage, for example, to underground pipes or the sewage system.
With Chinese reed, the barrier does not have to be as wide as with bamboo, for example. A width or depth of 50 cm is sufficient for this plant. First you have to dig a trench about 45 cm deep around the planting hole with a diameter of 2-3 m. The barrier is then placed there. Here, too, you should make sure that there is an overhang of about 3-5 cm at the top edge and that there are no stones behind the foil. Once the barrier has been installed, excavated earth can be filled up again and the reeds can be planted.
For Chinese reed you do not necessarily have to use a special rhizome barrier from the trade, an old plastic rain barrel or a so-called mortar bucket, which you insert into the ground like the foil and plant the reed in there, would be just as suitable for this. However, you would have to remove the bottom of both beforehand. After planting, Chinese reed should be watered regularly both in a commercially available rhizome barrier and in a barrel or bucket.
Installation of a rhizome barrier for raspberry plants
- It is also advisable to install a rhizome barrier for raspberries.
- The roots of this plant spread out to a radius of about 2 m.
- They can displace other plants relatively quickly.
- If you equip raspberry bushes with a root barrier, they then have to be watered more often.
- The roots of the raspberry are much softer than those of bamboo, for example.
- As a result, you can also use strong pond liner or special barrier films for the root barrier.
- After the excavation, these are then inserted at least 30-40 cm deep, with an overhang of 3-5 cm.
- Then the soil can be filled up and the raspberry can be planted.
- Finally, rinse thoroughly here too.
Install root barrier for sea buckthorn
Sea buckthorns are trees up to 6 m high or shrubs about 4 m high. The strong roots of the sea buckthorn grow widely, so that a suitable root barrier is also recommended for this plant. A ditch is also dug around the planting site for the sea buckthorn.
This should have a diameter of at least 1.50 m and be at least 60 cm deep. Then the respective barrier is used accordingly, the ends are closed professionally and the trench is filled with earth. Even with sea buckthorn, the root barrier should protrude a few centimeters from the ground.
need for a root barrier
A root barrier is particularly recommended for plants that form offshoots. It is intended to limit these foothills within a certain area and thus ensure controlled root growth. If such plants are not properly blocked, their runners can cause considerable damage, for example to paved areas, terraces, pond liners, underground pipes and cable systems, the sewage system and even buildings or their foundations.
If the root barrier is installed during planting, this can be done relatively easily. Subsequent installation is much more difficult and expensive. The perfect rhizome barrier must be able to withstand high pressure, especially with bamboo. In addition, it should be as smooth as possible on one side in order to offer the roots as little contact surface as possible.
Corresponding film for a rhizome barrier is available by the meter. To determine how many meters you need for a single plant, for example, you first measure the diameter of the planting hole and multiply the whole thing by three.
Subsequent installation of a rhizome barrier
The subsequent installation of a rhizome barrier is possible, but with a much higher effort. First of all, you have to dig a trench between 40 and 70 cm deep at a distance of between one and two meters from the plants. The distance to the plant depends on the respective plant species, with bamboo the greatest distance should be maintained.
Before you use the root barrier, you should dig up as many root suckers as possible that have already grown into the property or garden; cutting them off alone is not sufficient. Since you can usually hardly find all the runners, it can of course happen that new shoots appear elsewhere next year despite the root barrier.
The rhizome barrier is then inserted and aligned in the trench. Again, you have to make sure that it protrudes 3-5 cm from the ditch. Then the ends are either screwed together using a locking rail or welded. Now the trench can be filled with earth again.
Risks when installing a root barrier
The greatest risk is improper installation of the root barrier, with the closure point between the two ends probably being the greatest weak point, especially if the two ends have been overlapped. Especially with bamboo, this can lead to the roots breaking through the root barrier and then being able to spread unhindered despite the barrier.
The same problem occurs when the material used for the barrier is not strong enough or stable enough to withstand the pressure of the roots, or when the barrier has been placed too close to the root zone, constricting the roots.
Alternatives to a standard rhizome barrier
Most commercially available rhizome barriers are made of high-density polyethylene. For bamboo, these are probably also the safest. For other plants such as raspberries or reeds, there are also so-called root fleeces or spunbonded fleeces. These are relatively stable and can hardly be penetrated by normal roots. However, the connection point, which is usually only glued, also represents a weak point here.
Special roof foils, which are normally used to seal flat roofs, are usually very stable, but they are completely unsuitable for bamboo and an interesting alternative for other plants. The already mentioned mortar bucket or rain barrel made of plastic (PP), which are available in every hardware store, also work relatively well.
Most plants do not need a root barrier, but for a few, such as bamboo, raspberries, reeds or sea buckthorn, it is definitely recommended, if necessary also retrospectively. Because if the root suckers have already spread several meters, it is very difficult to get rid of them again. Proper installation of the root barrier and a correspondingly stable material are particularly important in order to be able to rule out possible risks from the outset.