Pruning, maintaining and reviving bamboo plants

By the end of the summer, many bamboo plants have masses of new shoots at the base, and many side shoots off established shoots. A bamboo can be transformed by a bit of artful grooming, and we do this to any that we look after. The stems can be shown off by removing the majority (70-80%) of the small, new shoots. You can also remove all the small side shoots emerging from the bigger stems (correctly known as "culms") up to a certain height. Doing this gives the plants a much more architectural appearance, and it encourages some stems to grow really sturdy and thick. By and large, bamboo should not be sheared or trimmed, though there are cases where this looks good - ie, in a hedge which needs to kept at a certain height.

A un-thinned bamboo on the left, a thinned one on the right.

Many bamboos, such as Phyllostachys nigra and Phyllostachys aureasulcata have beautiful stems, and pruning them in the above way helps to show them off at their best. You'll need a good pair of loppers to cut the culms successfully, such as those sold by Felco, and also a pair of gloves.

Follow the following guidelines for healthy plants, or if you are trying to revive unhealthy looking plants:

  • Firsty, although bamboos like moist soil, it does need to be well-drained. When in a water-logged situation bamboos can just sit there in a non-flourishing, sickly state for years.
  • Secondly, what is the physical structure of the soil? If it is poor soil, consider digging up the plants, loosening the surrounding soil with a fork and adding well-rotted manure. This will feed the plants and also allow the roots to spread and develop. Bamboos also grow better if their own leaves are left to rot into the ground at their base - this provides valuable nutrients, including silica which helps the culms / stems to develop.
  • A third point to consider is how the plants were planted. A lot of bamboos on sale in Ireland are quite pot-bound: in other words, the roots are densely entwined with one another in a solid mass. If no attempt is made to loosen the roots at the time of planting, and the soil is poor, the plants will hardly develop at all after planting. Roots need to be torn apart, and if plants are badly pot-bound they should be hacked at (gently) with a fork or spade.
  • If your soil is poor or waterlogged, dig up the plants and incorporate into the soil a few bags of manure (such as Gee-up), or home-made garden compost. If you don't think the soil is an issue, try watering them with a liquid feed regularly for at least two months. Any liquid plant food such as a seaweed based one, or even Miracle-Grow should lead to visible improvement.
  • Finally - wind. Some species, such as Phyllostachys aurea, just don't thrive in a windy spot, whilst others, such as Phyllostachys bissettii, can grow in a windy spot without a spot of bother. The most damaging wind of all is the cold North-Easterly wind of late spring - it can make a plant look really tatty.