An ornamental garden that uses nothing but rain, survived the Millennium Drought and, barring cyclones, should cope with whatever the climate is likely to throw at us over the next fifty years.
The original plan for the front garden was to showcase water-wise ornamentals. When I realised in 2004 that SE Qld was in deepening drought, plans for a garden needing a once weekly watering (my standard design), became instead a ‘crash test’, rain fed subtropical garden. Long lived plants, like palms and cycads, were chosen to suit the CSIRO’s predictions for Global Warming to 2050.
The native and exotic ornamentals here are not merely water-wise, most are drought-resistent. I foliar feed the garden with seaweed once or twice a year. Cycads are fed and watered during their annual growth burst. Only the native hibiscus hedge (Hibiscus insularis, an endangered species from Phillip Island in the Norfolk Island group) needs to be watered weekly during dry spells. This hedge acts as a windbreak, reducing evaporation in the ornamental garden. The hedge was raised from cuttings taken by the Growing Friends of the Royal Botanic Gardens, Sydney, from the type specimen. A botanical illustration of a flowering sample of this hedge now hangs in the National Herbarium of NSW.
In September 2004, I planted 150 plant taxa of ornamental, medicinal and food plants, some of which are threatened with extinction, including palms, cycads, bromeliads, succulents, ferns and bulbs. They were watered six times over five weeks before being abandoned to natural rainfall (which in this part of Brisbane can be erratic).
Unprecedented drought (2005 – 2010) was followed by summer floods (2011, 2012 and 2013) and most recently dry years of 2013, 2014 and 2016. The years 2015 and 2016 were the hottest on record. These were stressful periods for the garden, and helped reduce planted diversity to 135 taxa (stocktake, winter 2017).
The reality of drought has been erratic falls of brief, dumping rain often in the dry season as a result of East Coast Low Weather Systems in winter. Five frosts of 0.5C have occurred on the night following a winter East Coast Low, despite this being a usually frost free district. Spring hailstorms occur, the most damaging being in 2006, when Wynnum was declared a disaster zone. Long periods with no useful rain are common during the summer wet season.
The wettest day on record was 30th March 2017, when ex-Cyclone Debbie delivered 291mm rain in 24 hours. Heaviest single falls of rain have been: 56mm rain falling in 16 minutes on 24.1.12, and when 88mm fell in 30 minutes on 11.12.10. In all these cases there was no runoff, every drop was absorbed.
The driest dry season to date was winter 2004 (June to August) when the total rainfall was 31.75mm (the average is 176.5mm).
I removed the Agave mexicana, Carissa macrocarpa and the bamboo, Schizostachyum ‘Murray Island’, because they outgrew their allocated space and created unwanted maintenance. In 2014, I removed the Mt Spurgeon pine (Prumnopitys ladei) which was shading the solar panels. This specimen was propagated and is now in the collection of container plants.
The female specimen of Pandanus cookii proved to be a facultative apomict in 2016, producing viable seed without a pollen partner.
The Coquito de Chile palm (Jubaea chilensis), a threatened species of South American palm and feature plant at Bellis, germinated in 1995. It started producing a nut crop in winter 2011. During flood years, it also produces edible fruit. In 2016, the proprietor of Palms for Brisbane said this is the only seed producing specimen in Brisbane, although there is another in Ipswich.
Video from a 2007 Gardening Australia Expo presentation