Is your garden parched? Meg Liptrot says greywater could be a big help

Aren't we lucky to have an unseasonably sunny summer? Usually there are complaints about flooded campgrounds and opportunities lost, yet this is one for the history books for altogether different reasons.

Although it's not so much fun for people relying on the rain for essential crop and grass growth, or for those struggling on tank water, many of us have town water supply to use on our parched gardens. At the time of writing, showers are forecast for Auckland this weekend and early next week, which it's hoped will help those thirsty soils.

At our urban house, we have a 1000-litre rain tank hidden under the deck to supplement garden watering and to fill our small fishpond. This summer, I've rarely used the water directly for the garden because the tank hasn't been replenished by rainfall and I prefer to reserve this chemical-free water for the fish.

Instead of using perfectly good drinking water on the plants too often, I wait for pond cleaning time, and siphon the wastewater into a watering can and give our pot plants and garden a good soaking then.


Natural, beneficial bacteria keeps the pond algae-free, so the water is safe for plants and is nutrient-rich.

For safety's sake, avoid splashing re-used water (greywater) on anything you're going to eat directly, such as salad greens or fallen fruit. Greywater is best applied directly to the soil around ornamentals.

Having a greywater system makes a lot of sense when we get these dry conditions. This involves re-using laundry, shower and bathwater for irrigation, or plumbing it back into the house to flush the toilet. In Auckland's urban areas, resource consent is needed for on-land greywater discharge into gardens because of the close proximity to houses and potential health risks.

There are greywater systems out there which filter and treat water before re-use, and which are approved by Auckland Council, particularly in water-short spots such as Waiheke Island. In the island's case, the price for resource consent has dropped significantly when using the approved system.

Many rural properties need to discharge greywater as they are not connected to metropolitan wastewater services. In this case, greywater is an asset for gardens.

Hawkes Bay and Kapiti Councils also have progressive greywater policies.

I occasionally re-use bathwater in times of extreme dryness by lugging bucketsful of it to the garden. Our lemon tree was showing the first signs of leaf yellowing, with darker veins on the older leaves (chlorosis). The lack of water had reduced the tree's ability to take up magnesium from the soil solution. I'd had an Epsom salt bath (magnesium sulphate) for my sore gardener's back, so the wastewater was perfect as a fix to put magnesium and water in the soil around the lemon tree without changing the soil pH.

Ensure you use only phosphate-free eco-detergents and real natural cleaners in your household water. That way you are less likely to cause pollution when re-using this water in the garden.