Your gardening questions answered: When should you cut bamboo?

Q: What time of the year should you cut bamboo? AH

A: Prized for their statuesque appearance and handsome evergreen foliage, bamboos can make fine focal plants in a garden, while also providing valuable shelter and privacy as hedging or screens. But that description comes with an important caveat, which is that the term “bamboo” is an umbrella expression referring to a very large number of different species including some that are potentially invasive. Known as “runners”, these have strong, wiry roots and rhizomes (underground stems) capable of spreading many metres in the soil and potentially causing damage to lawns, flower beds, paving, walls, drains and other garden structures. Examples include Arundinaria, Phyllostachys, Pleioblastus, Pseudosasa and Sasa. However, others are known as “clumpers” on account of their relatively mannerly growth habit. Examples include Bambusa, Chusquea, Fargesia, Shibataea and Thamnocalamus.

Pruning should be carried out in spring, using a sharp secateurs to cut any unwanted canes back down to ground level and reduce congestion

Running bamboos aren’t suitable for growing in an Irish garden unless the planting hole is completely contained with a high-quality, very strong, impenetrable root barrier membrane, or they’re kept in a large tub or container. Even then, it’s important to check regularly to make sure that their probing root systems haven’t surreptitiously escaped. Both clumpers and runners form strong, thick, substantial root balls that are very difficult to remove once established in the ground.

You don’t say why you want to cut back your bamboo, but if you’re really struggling to keep its growth in check, then I’d recommend removing it entirely on the basis that it’s probably a running species. In this case, you have two options. One is to keep cutting the canes back down to the ground to eventually exhaust the plant, a process that will take time and persistence. The other is to excavate and remove as much of the roots and rhizomes as you can, a challenging and back-breaking job that may require the help of a professional landscaper and the use of a mini-digger. For more advice on eradication, see https://www.rhs.org.uk/plants/types/grasses/bamboo-control

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On the other hand, if your bamboo is one of the many relatively well-mannered clumping species and shows no signs of being invasive, then there’s no need to take such an extreme approach. Instead, pruning should be carried out in spring, using a sharp secateurs to cut any unwanted canes back down to ground level and reduce congestion. Nipping the tops off any canes that have got too tall will also contain their height and encourage the plant to bush up. Finally, removing some of the lower foliage is another great way to show off those sculptural canes and allow air and light to filter through the plant.