If you’re watering plants with grey water, the type of detergent you use really makes a difference to both their health and the health of the soil.

It’s the soil fungi – mycorrhizal fungi – you need to tend as well as your plants. That’s why we feed the soil with compost – it keeps beneficial microscopic soil organisms happy and they help sustain plants through tough times.

Mycorrhizal fungi live in intimate association with roots – sometimes they surround or even envelop young feeding roots and commonly they penetrate the roots, plumbing plant and fungus together as one. Orchids, ferns and members of the Proteaceae family – Grevillea, Banksia, Protea and Leucospermum, etc, are especially reliant on mycorrhizal fungi and are easily harmed by common brands of detergent. Coral is also highly susceptible to phosphorous and detergents in sewage water.

In drought, mycorrhizal fungi act as an extended root system for plants, searching for water. Their vital work also helps defend their host plants against disease, and they contribute to plant nutrition. In return, plants supply carbohydrates to help the fungi prosper – it’s a mutually beneficial (symbiotic) relationship.

Avoid cleaners containing bleach and avoid reusing dishwasher machine water. Mycorrhizal fungi can be killed by chlorine bleach (which forms persistent carcinogenic chloramines on contact with organic matter) and they can suffer terminal damage when certain mainstream detergents – that take forever to biodegrade – are used.

Dishwashing machine detergents can be highly alkaline and can harm both roots and soil microorganisms.

Australian advertising laws are so lax they enable manufacturers to all claim their products are biodegradable, however whether they degrade in ten days or ten months is never advertised.

I have been watering my crops using recycled water containing green cleaners since 2003 (see examples in images). Results from my crops at Bellis have been so promising that during the Millennium Drought the Queensland government amended some of its grey water advice to gardeners.

There’s also a useful book on the topic:

‘GREEN CLEAN: The Environmentally Sound Guide to Cleaning Your Home’, in paperback, by Linda Mason Hunter and Mikki Halpin, Published in 2005.

Happy plants grow in healthy soil, even in drought.

Jerry Coleby-Williams
Director, Seed Saver’s Network
Patron, Householder’s Options for Protecting the Environment
Patron, National Toxics Network
7th February 2019