Bamboos

Bamboos are highly desirable, attractive ornamental plants that bring a touch of the exotic to our gardens. But some species are incredibly vigorous and produce thick creeping roots (rhizomes) that can spread, get out of control and grow where you don’t want them to.

The stems (canes) then grow up and become a nuisance or major problem – especially if that is in between paving slabs, in vegetable gardens or through other plants.

Because the rhizomes can spread some distance, you may find that it’s growing through from your next-door neighbour’s garden!

Not all bamboos are problematic – many are clump forming that don’t tend to spread. Running bamboos include Chimonobambusa, Pleioblastus, Pseudosasa, Sasa, Semiarundinaria and Sinobambusa.

• Beds
• Borders
• Lawns
• Gravel paths
• Between patio slabs
• Waste or uncultivated ground

Bamboos are members of the grass family (Poaceae or Gramineae) producing tall, thin, evergreen stems that can reach a height of 3m (10ft) or more, depending on species. These produce sparse, thin leaves.

Running bamboos have fast-growing rhizomes (roots) that can spread over great distances. These usually have a very sharp, tough tip, which grows easily through the soil and can even grow up through concrete and tarmacadam.

Japanese knotweed – a noxious, invasive, deep-rooted perennial weed – is often confused with bamboos.

As with most difficult perennial “weeds”, never allow running bamboos spread to where you don’t want them to grow. If you do, it will make it more difficult to control and become more of a problem.

Wherever possible, start by digging out the clumps of plants, including the rhizomes. These may be tough and deep in the soil, and you may have to use a pickaxe or similar.

Then, repeatedly dig out any regrowth as it appears to exhaust the energy remaining in the rhizomes. This could take several years to give full control.

Covering the soil with weed-control membrane (landscape fabric) or even thick black polythene to exclude light will have no effect on bamboos, since the rhizomes and stems will simply grow through them.

In lawns, regular mowing throughout the year may weaken it and keep it under control.

There are a number of weed control options available to treat sow thistles. In addition to traditional weedkillers there are now also a range of more natural alternatives.

For best results, spray with a systemic weedkiller. A systemic weedkiller, which is absorbed by the leaves, then moves down to the roots to kill them.

To ensure the weedkiller works effectively:

• Spray the plants when they’re growing actively; this is mainly from April/May to September.
• The larger the leaf area present, the greater the amount of weedkiller that can be absorbed and move down to the roots. So don’t bother spraying when the growth first emerges through the soil – wait until the stems are around 60-90cm (2-3ft) high.
• Tall bamboos will be difficult to treat with a spray weedkiller, so cut down the canes first and then treat the re-growth. The younger leaves will also absorb the weedkiller more effectively.
• Use a fine spray to thoroughly coat the leaves in small droplets.
• During the summer, spray in the evening to prevent the spray evaporating and to give maximum time for the spray to be absorbed. In spring or if overnight dew is forecast, spray earlier in the day to allow the spray to dry before dew falls.
• One application of weedkiller is highly unlikely to completely kill it. You will need to spray once, allow it to die down, and then spray the regrowth again. Three or four applications a year, over several years, may be needed to completely kill it, depending on how extensive the root system is.

Tough formulations of weedkillers, or tree stump and root killers, will be more effective than the standard formulations.

A gel, which is smeared onto, and sticks to, the leaves, may be a better option than a liquid spray.

Contact weedkillers will damage or kill any plants whose leaves it is sprayed on. Make sure you keep the spray off wanted plants – including lawns – and, if necessary protect plants by covering with polythene or similar when spraying.

Use weedkillers safely. Always read the label and product information before use.

If bamboos start to spread where you don’t want them to grow, cut off the rhizomes with a sharp spade. It is easier to do this annually, rather than wait until their excessive growth becomes a problem.

If the growth is coming from a neighbour’s garden, have a quiet word and try and encourage them to control it in their garden.

When planting varieties of spreading or running bamboos, it pays to plant them inside a physical barrier to stop the rhizomes spreading in the first place.

Dig a planting hole at least 60cm (2ft) deep, but ideally 90cm-1.2m (3-4ft) deep, and line the sides with a solid, impervious material, such as paving slabs or corrugated iron sheets. Make sure there is a tight fit, with no gaps between the materials and corrugated iron sheets overlap by at least 30cm (1ft). The barrier must protrude at least 7.5cm (3in) above soil level, to prevent the bamboo rhizomes “jumping” over the top.

• Spade
• Fork
• Secateurs
• Weedkillers