How deep does root barrier for Bamboo need to be?

When bamboo has started its spread, prevention is required before any damage is done, or relationships with neighbours become strained. One of the most effective methods for containing bamboo growth is to install a root barrier, a product which allows drainage to occur whilst preventing roots and rhizome from escaping. Of course, to be effective root barriers need to be properly installed. This opens many questions including: what type of barrier should be used? And, how deep does root barrier for Bamboo need to be? Before answer these questions, it's useful to understand how bamboo spreads.

Bamboo Roots and Rhizomes

Bamboo has both roots and rhizomes. The roots are there to absorb water and nutrients. Generally, bamboo roots are quite tough and fibrous but, although they’re great at binding soil together, they’re not strong enough to do any damage. The roots grow from the bamboo rhizomes which, by contrast, are incredibly strong, can grow extremely quickly and do cause damage.

Rhizome is actually stem that grows in the ground or along the surface. Bamboo rhizomes have the job of storing water and nutrients, as well as enabling the plant to spread from one location to another and create new upright stems. Buildings, drains, paving, ponds - just a few of the things that can suffer when bamboo rhizome encroaches. Telling the difference between bamboo rhizome and bamboo roots is easy - the roots look like, well, roots, and the rhizomes look very similar to those familiar noded stems.

Rhizomes, are in fact stems - they just happen to be in the ground or lying on the surface. Their job is to store nutrients and water and to provide places from which new upright stems can grow. Roots often grow from the underside of a rhizome (this is the case with bamboo). Rhizomes tend to be thicker and tougher than roots. Many plants have rhizomes, including ginger, calatheas, poplar trees, bamboo and then there is the highly problematic Japanese knotweed rhizome. This one can prevent property sales going through, and whilst this typically doesn't happen with bamboo it is become the source of neighbour disputes.

Running Bamboo

You’ll likely have heard about running bamboo which, as the name suggests, isn't slow to spread. Within two or three years of planting, most ‘runners’ will start to spread outwards, with rhizomes growing laterally in the soil. This can go unnoticed for several years. Then, when new shoots appear from the rhizomes, it looks like the Bamboo has suddenly grown many metres in all directions.

Clumping bamboo

Another type of Bamboo is ‘clumping’ or 'clump-forming' bamboo. Rhizomes of clumping bamboo usually grow more slowly than runners and they have a tendency to curve upwards. This means that they appear far more manageable. After many years in one spot, however, even clumping Bamboos can put on a bit of a spurt, and rhizome spread can happen quite rapidly for a time.

N.B. Given the UK's colder conditions (than that of native Asia), some species of running bamboo may exhibit different characteristics over time. When first planted, and even for several years, it may remain confined (like a clumper) then suddenly send out runners to expand.

How Deep are Bamboo Roots?

In general, the rhizomes of most bamboo species will grow in the topsoil most of the time - that’s normally 200 to 300 mm. Bamboo roots (the thinner strands) tend to grow downwards from the rhizome, so these will go a bit deeper, down to around 500 or 600 mm. The caveats are that not all types of bamboo have the same characteristics and that, sometimes, bamboo does unexpected things based on conditions and environment.

Bamboo root depth and rhizome depth for the larger varieties may go deeper into the soil, so if you are planning on putting in a root barrier, it pays to know what kind of bamboo you’re dealing with first.

Secondly, most bamboo species are amazingly good at finding a water source. Therefore, you may find bamboo deeper in the soil where there’s a leaking pipe or water feature. In fact, any hard landscape feature that traps water underneath or on one side, like a retaining wall for instance.

Bamboo barrier depth

The question of how deep root barrier for bamboo needs to be installed has a straightforward answer but with some caveats. For a standard bamboo roots depth and rhizome depth of around 250 mm, a root barrier set at 500 mm will be very effective in nearly all circumstances.

Most of the root barrier installations we conduct are at a depth of 500 mm in the soil, with a 100 mm ‘upstand’ of barrier above the soil. Visit the PBA Solutions website for more information about our root barrier installation service. However, if you feel capable of installing a bamboo barrier yourself, start here: 
Guide to Installing Bamboo Root Barrier

Bamboo planting location

If you intend to plant bamboo within a couple of metres of a water source, or hard landscaping feature (e.g. retaining walls), it’s worth considering putting in a deeper barrier - to a depth of around 800 to 900 mm. This should also be a consideration when land around the bamboo is uneven; dips and humps along the line of the barrier need to be accounted for.

In theory, the deeper you can go as a safeguarding measure the better, but you will create more work for yourself. And, there is some debate about the reaction of bamboo rhizome at deep depths - should a rhizome escape here it may never resurface. Typically, bamboo prefers to expend its energy expanding its rhizome network closer to the surface.

Bamboo rhizome can also extend long distances above the soil if it needs to. However it also has the capability to extend over low obstacles with relative ease, hence the need to include above-ground barrier. All of these characteristics make it vital to contain your bamboo, and where necessary cut and remove visible rhizome attempting to climb.

If you are considering planting bamboo in your garden, first do your homework about the bamboo species you have in mind. It’s relatively easy to find out this information, and it will provide you with a better gauge of whether the gorgeous specimen you have your eye on is likely to remain within your borders. Even then, given bamboo's ability to change it characteristics - based on conditions and environment - bamboo barrier for containment is a sensible precaution.