Conserving Water in the Home Nursery

Max and Regina McDowall

When Stage III Watering restrictions were imposed on Melbourne with two weeks notice, just one week before Christmas, we wondered how we would manage to keep the nursery and stock plant collection of 30-35 sq. metres alive through the summer heat on two watering days per week, without a rain-water tank. Fortunately, we were able to get an exemption, for the nursery only, on the two other days allocated for odd house numbers, to use the microsprays for 7 minutes per day, and we would have to manage manually with grey water from watering cans on the other three days.

However, before we knew whether we would get the exemption, we proceeded to put the entire nursery into styrofoam boxes lined with 20 micron polythene sheet to a depth of 2 cm and 8 thicknesses of newspaper. We took the opportunity to weed the pots as we went, adding additional nutricote and topping with about 1 cm of small 5-7mm white pebbles to cut evaporation by reducing capillary action and reducing the surface temperature by reflection of sunlight. Now all water falling within the perimeter of the box is retained up to a depth of at least 1cm, and to remain available for the plants for at least one more day, except on very hot days, As a result, we have been able to cancel some scheduled watering periods on the cooler days and instead store about 100-120 litres in buckets including some cleaner grey water for manual watering on hot off-days. As a result the plants are thriving.

Possible problems

1. We are concerned that continued accumulation of nutrients from the normal leaching of the nutricote will eventually result in excessive levels in the potting medium, especially for proteaceae species.
   
   
2. Some of the plants may not like extended periods of wet feet. In the absence of aerial root pruning, others may produce excessive root growth, out of the bottom of the pots.
   
   
3. The build-up of nutrients and potting medium in the boxes may encourage the growth of algae and other pathogens. Accordingly we intend to rotate the nursery over a period of about 4-6 weeks during cooler or wetter weather through unlined polyboxes for 3-4 days in turn, to enable watering cycles to flush out the excess nutrients, and to enable the lined polyboxes to be cleaned and checked for leaks. This will be require a lot of extra work, and we have yet to start the first cycle.

Note: We are getting sore arms and shoulders from hauling and holding buckets and watering cans of water, especially as we had pre-existing injuries, and now carry only half-full buckets. We now collect most of our dirtier grey water from the showers and laundry in a converted 240 litre recycle bin and pipe it onto garden beds or into buckets down the block. Water is bailed from any full buckets into the watering can using an old kitchen pot.

From the newsletter of the Grevillea Study Group, February 2007.

Australian Plants online - 2007
Association of Societies for Growing Australian Plants