The escalating impact of climate change is forcing many of us, especially in the Southwest, to reconsider how we use and conserve our water resources. Many homeowners are replacing their lawns with stones and succulents. Those with a bit more ingenuity are reconfiguring their plumbing to recapture gray water and irrigate their gardens. For those who love to keep their grass and bamboo green throughout the summer, gray water is an excellent option.

Bamboo is an incredibly resilient plant that can thrive in poor soil and is ideally suited for taking gray water, the untreated runoff from sinks, showers and washing machines. The shallow roots of bamboo require fairly regular irrigation, so it’s environmentally sensible to use recycled water for that purpose. Furthermore, bamboo’s dense network of rhizomes are very effective at phytoremediation, the process of using plant matter to filter water and even remove heavy metals.

What is gray water?

Gray water, or grey water, refers to the untreated excess water that drains from you sinks, showers, dish washers and washing machines. This water has been used and is not suitable for drinking. But generally speaking, it’s OK for watering plants.

We call it gray water to distinguish it from black water, which is the highly contaminated water from the toilet which contains toxic human waste. This water should not been used in the garden, as solid human waste is capable of carrying dangerous bacteria like E. coli.

Ordinarily, household plumbing does not differentiate between gray water and black water. All used water goes down the drain and ends up heading to the same septic tank or waste water treatment facility of your local municipality.

Recycling your gray water

If you hire a plumber, or you’re fairly handy yourself, you can separate the pipes and redirect your gray water into your garden. Normally, you can do this with any outgoing water except the toilets. The greatest quantities of gray water usually come from the washing machine and the dishwasher.

If your gray water is going into a vegetable garden or to irrigate any other plants meant for human consumption, you should be very careful about what sort of soaps and detergents you’re using. Look for something natural and biodegradable.

But even if you’re just watering ornamental plants, you don’t want to deposit chemical suds into your soil and ground water. So I’m a big fan of Seventh Generation products, which you can easily order from Amazon.

Bamboo as a natural water filter

Because of its dense underground rhizome system, bamboo is especially well-suited for phytoremediation. This is the natural process by which plant tissue absorbs contaminated water and removes, stabilizes or destroys certain harmful substances.

Therefore, if you are flushing conventional soaps into the gray water and directing it into the garden, bamboo should be the first stop. You might, for example, have a hedge of bamboo running along the highest end of the garden. You can feed the gray water into the bamboo, and let it percolate through the soil. From there, the water, now somewhat cleaner, will trickle down into the other plants.

A hyperaccumulator

Recent research also indicates that some species of bamboo have the capacity to remove heavy metals from the soil. Bamboo’s dense fibers, the same property that makes this grass resemble a hardwood, can absorb large amounts of toxicity. We call these kinds of plants “hyperaccumulators”.

Bamboo is one of very few plants that is both fast-growing and a hyperaccumulator. This combination makes it an ideal choice and a valuable tool for cleaning contaminated soils. But further research is needed to determine which species of bamboo are the most effective for this purpose.

Further reading

If you found this article about bamboo and gray water useful and insightful, you might also take a look at some of our other in-depth blog posts.

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