Tree care: Bamboo is the new Japanese knotweed

WHEN I visited the wet, humid tropics, bamboo was one of the first things I noticed – huge, dense thickets with canes as thick as a man’s forearm and 10 metres tall. I had seen bamboo before in our local park, once a Victorian estate with huge clumps of bamboo in what was left of the Japanese Garden, almost certainly in excess of a century old. But I never thought I would see the day when bamboo in Britain would join all those now invasive trees, shrubs and vegetative plants that were brought here centuries ago as ornamentals, in what seemed like a good idea at the time. 

I am talking about plants such as Japanese knotweed, Himalayan balsam and Rhododendron ponticum – invasive, highly damaging and costing a small fortune to manage. No chance of eradication here. 

Bamboo comes in two different ‘growth’ types: clumping bamboos (clumpers) and running bamboos (runners). Clumping bamboo possesses a non-invasive rhizome structure (known as pachymorph rhizome), differing from the better known – and now feared – running bamboo with its leptomorph rhizome. Clumping bamboo forms a tight cluster of gently arching culms, extending from a relatively small root mass. Running bamboos are the ones that spread by rapid growth of long, horizontal rhizomes. 

Experts claim clump-forming bamboo is the best and safest bet, unless you have a lot of space to fill, when presumably you might logically opt for a running bamboo.

But you could soon find your newly established bamboo is filling more space than you bargained for. 

Like Japanese knotweed, bamboo can grow through literally anything – including concrete. It will readily jump the boundary fence into your neighbour’s garden, invade the foundations of your house and even grow upwards to live with you. This means you might not be able to sell your house because your prospective buyers won’t be able to secure a mortgage until the tropical triffid is eradicated. All these scary stories essentially refer to running bamboos, but it’s interesting to note that experts don’t say clump-forming bamboo is safe – only safer. 

Bamboo has become the next Japanese knotweed, according to Emily Grant, director of operations at Environet, a specialist company in the surveying and removing of invasive plants. She told the Guardian how the most significant difference between bamboo and Japanese knotweed is the gardening public’s awareness. 

Environet recently added questions about bamboo to its annual survey, conducted by YouGov. “In our latest research, 71 per cent of people weren’t aware that bamboo could cause any damage and 84 per cent were not aware that it could prompt legal claims between neighbours or hinder property sales,” said Ms Grant.

Furthermore, bamboo is frequently planted intentionally on garden boundaries as a natural living fence, which means the probability of disputes between neighbours is more likely with bamboo than with other plants. Because bamboo may take up to 10 years or more before it reaches maturity, the problem is often passed on to blissfully unaware future owners or tenants. 

It is strange, therefore, that there are no restrictions on planting bamboo or any legal requirements to declare its presence when selling a house, as is the case with Japanese knotweed. That’s because it is not legally classified as an invasive species, but a fast-spreading bamboo plant may be just as destructive as Japanese knotweed.

Inquiries about bamboo flood Environet’s Surrey HQ at a rate of 20 a day during the summer months when bamboo undergoes its most rampant growth. “We started out as 100 per cent focused on Japanese knotweed, but in the three years since we started to offer bamboo removal services, it’s now about 50:50,” said Ms Grant. “And it’s not that we were turning away bamboo work before. We just weren’t seeing the demand.”

Bamboo is highly attractive but you might get more than you bargained for. (Image: Stock)

We never seem to learn from the consequences of bringing in alien and potentially invasive ornamental plants because they look good. Japanese knotweed, Himalayan balsam and Rhododendron ponticum (RP) fall into this category with RP showing another dimension to the catastrophic damage it can wreak. Apart from the damage caused to woodlands and other ecosystems and habitats, due to its invasive nature, RP is also a sink and repository for Phytophthora ramorum by providing an unrivalled foliar template for spore production and dissemination. 

If it were not for RP and its ability to support the generation and release of such a huge numbers of P. ramorum spores then it is questionable whether the P. ramorum pathogen could have successfully jumped to infect Japanese larch.