Numerous ornamental plants develop considerable root systems over the course of their lives, which grow under garden paths or penetrate cracks in facades. To prevent this, plants that are willing to spread should be provided with a root barrier. This is also suitable for plants that spread uncontrollably in the garden.

Root barriers are a must for rampant plants in the garden

Table of Contents

Show all
  1. the essentials in brief
  2. Buy root barrier
  3. Application of the root barrier
  4. Root barrier - alternative
  5. Which plants restrict?
  6. No root barrier necessary
  7. frequently asked Questions

    8. the essentials in brief

    • Conventional root barriers are made of plastic and have to withstand the soil climate. Metal alternatives are uncommon.
    • The material is laid perpendicular to the walls of the planting hole. For most plants, foils with a width of between 20 and 80 centimeters are sufficient.
    • DIY stores offer their own brand products and high-quality manufacturers at prices between seven and 14 euros per meter. Favorable alternatives are dimpled membranes or recycled material leftovers and old vessels.
    • Numerous ornamental grasses as well as berry bushes and ornamental trees require root barriers. Some herbs and climbing plants also form root suckers.

    Buying Tips

    Flexible root barriers are supplied in roll form and are typically two millimeters thick to withstand root pressure. You can determine the dimensions yourself and cut the foils. Plastic is a common material for a root barrier. There are alternatives made of metal for certain areas of application.

    Properties of an ideal root barrier:

    • resistant to chemicals and solvents
    • acid, salt and alkali resistant
    • resistant to mold and microorganisms
    • to protect cables with waterproof coating
    • free of plasticizers and toxins that could get into the soil

    plastic

    Plastic root barriers are mostly used

    The material offers the great advantage of flexibility. According to a study by the Weihenstephan University of Applied Sciences, a film 70 centimeters wide provides the best protection against root pressure for most ornamental plants in the garden. Root barriers made of polyethylene or polypropylene are common. The foil ends are connected with aluminum rails that can be screwed together. Root suckers cannot grow through these splints. Many manufacturers grant a 25-year material durability guarantee for their products.

    polyethylene polypropylene
    shortcut HDPE pp
    properties particularly high density and resistance easy handling due to low weight
    notice Laying requires more effort not suitable for bamboo

    Metal root barrier

    Since most metals do not have any protection against corrosion, they are not suitable for permanent use in the ground. An alternative with an unfavorable price-performance ratio would be stainless steel. However, there are metal root barriers that are offered specifically for lawns. This prevents the lawn from spreading on paving stones or growing into flower beds. Galvanized metal rails made of aluminium, stainless steel or steel are used, which are embedded vertically in the ground.

    Application of the root barrier

    youtube

    Dig the planting hole and completely line the walls. Make sure that the foil is lying vertically. Slight inclines result in the roots being directed upwards. Cut the foil so that the ends overlap 4 to 20 centimeters. The plants are then planted and the hole filled with topsoil. The overlaps must not be pulled apart. You can also seal the foils with butyl tape or aluminum rails.

    How deep is the root barrier laid?

    The depth depends on the respective plant species. A film 70 centimeters wide is usually sufficient to suppress the formation of runners in most plants. Many vigorous herbs and shallow-rooted berry bushes conquer depths of between 20 and 50 centimeters with their root system. Depending on the species, imposing ornamental grasses are restricted with a root barrier that reaches 60 to 80 centimeters deep into the ground.

    Alternatives for root barriers

    In numerous hardware stores you will find a wide selection of high-quality branded products and inexpensive alternatives to private labels. For smaller plants, used tubs or leftover material are usually sufficient, from which you can make root barriers yourself.

    broad material Price per square meter providers
    Gardol root barrier 70 cm pp 11.40 euros bauhaus
    Root barrier FloraSelf 65 cm Synthetic fiber with HDPE coating on one side 8.79 euros Hornbach
    Root barrier Premium 70 cm high-tech material 13.33 euros obi
    Dilator root barrier 70 cm pp 12.85 euros stretcher
    B1 root barrier 60 cm hard plastic 7.14 euros toom

    Recycle vessels and leftover materials

    If it is a small perennial with a high propensity to spread, you can put the root ball in a disused mortar bucket and sink it into the ground. You should not use containers made of untreated metal, as these will rust due to moisture in the earth.

    Many ornamental grasses or sea buckthorn can be planted with conventional roofing membrane. The roots of the vigorous raspberries can be contained with fleece that is laid to a depth of 40 centimetres. You should make sure that the material ends are connected to each other.

    Roof foil, garden fleece or buckets can be used as a root barrier for some plants.

    Dimpled sheet as a root barrier?

    The insulation layer for basement rooms is suitable as a root barrier if the material offers the same properties as conventional barrier film and the dimensions are correct. The most common Gutta dimpled membrane 'Star' has a material thickness of eight millimeters and is between 50 and 100 centimeters wide. It consists of durable HDPE and, with an average price of 1.80 euros per meter, is cheaper than a root barrier.

    Which plants to restrict with root barriers?

    Each plant has different propagation strategies and competitive strengths. Weak species put their energy into developing buds and seeds, so they don't pose a problem. Strong herbs, grasses and shrubs conquer large areas in a short time by developing underground runners.

    tips

    If you plant herbs such as mint or goutweed in the garden, you should also think about a root barrier here. A large plastic pot sunk into the ground will do.

    grasses

    Chinese reed should definitely be planted with a root barrier

    Sweet grasses include annuals as well as perennial and perennial species, many of which are planted as ornamental grasses in the garden. Their growth can be broadly divided into two categories. Grasses that form dense or loose clumps are usually site-specific and do not grow uncontrollably in the bed. The lawn-like growth form results from runners that creep on the surface of the earth or are formed underground by the roots. Such species need a rhizome barrier:

    • Chinese reed Eulalia (Miscanthus sinensis 'Gracillimus') forms roots at depths of between 30 and 40 centimetres
    • Chinese reed (Miscanthus sinensis) develops roots about 50 centimeters deep
    • Zebragrass (Miscanthus sinensis 'Zebrinus') roots reach 50 to 70 centimeters into the soil
    • Japanese blood grass (Imperata cylindrica) roots 60 to 100 centimeters deep
    • Giant Chinese reed (Miscanthus × giganteus) grows up to 100 centimeters deep
    • Reeds (Phragmites australis) can develop roots up to two meters deep

    background

    This is how bamboo grows

    Bamboo is a subfamily of grasses, the species of which form two different rhizome bodies. The first growth form is characterized by short and thick rhizomes. They develop more or less compact clumps that grow separately from each other.

    Long and thin rhizome bodies are characteristic of the second growth form. Such bamboo species grow more openly, so that the culms are evenly distributed over a wide area. They are considered to be willing to spread, which is why a root barrier for such bamboo species at a depth of 60 centimeters makes sense.

    trees and shrubs

    A tree develops strong roots over the course of its life that can cause damage to buildings or paving stones. How deep the roots reach into the ground depends on the species. Deep-rooters reach a root depth of between two and four meters, while shallow-rooters develop their root system far-reaching in the top soil layers. Many of these trees require a root barrier because they spread via underground runners.

    tips

    Wisteria is a climbing plant that roots deep and shallow at the same time in search of water. Therefore, a root barrier for the wisteria at a depth of 70 centimeters makes sense.

    ornamental shrubs

    Root barriers with a thickness of three to four millimeters and a height of between 45 and 50 centimeters are sufficient for most shrubs. Hydrangea, ranunculus or magnolia are particularly prolific and should be limited with a four to ten millimeter thick barrier film depending on their root thickness.

    How deep root barriers must be:

    • Thuja: 70 to 80 centimeters
    • pasture: between 30 and 50 centimeters depending on the species
    • Rosa rugosa: 60 to 70 centimeters

    The vinegar tree is a good example of shallow-rooted trees. On sandy and nutrient-poor soils, the species proliferates within a radius of ten meters around the trunk, where it forms vigorous thickets. Root barriers with a thickness of 10 to 15 millimeters are recommended.

    fruit bushes

    Blackberries and raspberries should be planted with a root barrier

    Many fruit bushes are known for their willingness to spread and take up large areas within a very short time. It is not uncommon for the trees and shrubs to spread in a radius of more than two meters and suppress any vegetation in this area. This growth is typical for shrubs from the rose family:

    • wild blackberries require root barriers at a depth of up to 30 centimetres
    • similar dimensions for varieties such as the 'Navaho' blackberry
    • Root barrier for raspberries should be 40 centimeters deep
    • Blackthorn is planted with a 50 cm deep root barrier
    • Aronia root barrier should reach 60 centimeters deep into the soil

    When are root barriers unnecessary?

    In contrast to its namesake, summer lilac does not need a root barrier, because the shallow-rooted shrub does not form any underground runners. Syringa vulgaris reproduces via root suckers, which can become annoying in certain situations. Therefore, a root barrier for lilacs makes sense.

    Plants that can do without a root barrier:

    • Pampas grass (Cortaderia selloana) forms attractive clumps
    • Chinese reed varieties of the 'condensatus' variety usually grow in clumps
    • Sacred Bamboo does not develop suckers

    frequently asked Questions

    What is a root barrier?

    A root barrier prevents a plant from spreading uncontrollably via underground runners in the garden. Permanent foils are commonly used to prevent roots from growing into unwanted areas. The term rhizome barrier is used synonymously. Such root barriers are available from Bauhaus, Hornbach or similar hardware stores.

    What is the difference between root barrier and root guide?

    Root barriers are smooth foils that lead to the so-called flower pot effect on trees. The shallow-growing roots spread left-handed and circular on the smooth-walled barrier. Since the tree loses stability with increasing height, the root guide was developed. Such systems contain vertical ribs that guide the roots down. Once these have reached the lower edge of the barrier, they continue to grow in their natural direction of growth.

    Is a root barrier necessary?

    Whether or not you should integrate a root barrier into the soil depends on the particular plant. A barrier film is unnecessary for species that grow in clumps, as they do not spread via underground foothills. Flat-growing ornamental grasses and herbs or berry bushes that are easy to spread should be equipped with a root barrier if uncontrolled growth is not desired. For smaller plants, you can use alternatives such as roofing foil, or place the plants in a permanent plant pot and sink it into the ground.

    Does the fig tree need a root barrier?

    The common fig belongs to the heart roots, whose root system is wider than the crown and develops a hemispherical shape. It is usually not necessary to root block the tree. The root system needs space to thrive. Since figs in Germany are preferably planted in sheltered locations or grown as a trellis on the house wall, a root barrier makes sense as a foundation protection.

    Can I plant bamboo without a root barrier?

    Whether your bamboo needs a root barrier depends on the species. There are clumpy growing representatives that do not need a root barrier. Flat-growing ornamental grasses tend to spread uncontrolled and should be restricted with an underground barrier. If you plant bamboo, a root barrier with a width of 60 centimeters makes sense.

    • a bamboo plant gets a root barrier with a diameter of 150 to 200 centimeters
    • The top of the barrier should be about two inches above the ground
    • Foil is laid in such a way that the diameter at the bottom is smaller than at the top

    Can I retrofit a root barrier?

    Although it is possible to integrate a root barrier in the garden afterwards, it is not recommended. Strongly proliferating plants such as bamboo develop a far-reaching root system and can also sprout again from rhizome pieces that have been severed. Dig a trench around the plant that is larger in diameter than the root ball. During this work you will come across the underground spurs that you will have to cut through with a spade and pull out of the ground.

Category:

Care tips