Rain garden

It’s raining – proper rain that is soaking the ground and has been falling on an off through the night and this morning. So I thought I would revive the following piece, written in 2009.

The Western Bay of Plenty is renowned for its plenty, including plenty of rain. But how many home gardeners are aware they can help slow and treat the run-off from their property by creating a rain garden?

Tauranga City Council has developed a rain garden at a reserve in Pillan’s Point, although engineering technologist Celia Bowles said it was still at an experimental stage.

“We’re building up our expertise on the design, maintenance and operation of a rain garden,” she said, “but there aren’t any plans yet to put more in.”

Kip Cooper, a civil engineer with Beca, said rain gardens can be useful in private or commercial situations – as well as controlling the volume of water flowing from a property, they can also help control the quality of the water running into Tauranga Harbour by removing contaminants such as zinc (from roofs), copper (from, say, spouting) and sediment.


A green roof and rain garden at Auckland Regional Botanic Gardens. Photo: Sandra Simpson

“If you have a place where you always wash your car, you could allow the run-off to wash through a rain garden before it enters the stormwater system to help remove contaminants,” Kip suggested.

The commercial application of rain gardens sees them positioned beside busy roads and in carparks to filter road and vehicle contaminants from rain water.

“In that situation, you have to choose plants that can cope with heavy metals,” he said, “and reeds are pretty good at that. There are plants that can store the contaminants or break them down.”


The 2008 rain garden by Auckland designer Kirsten Sachs. Photo: Sandra Simpson

Rain gardens can be as elaborate as the one designed by Auckland landscaper Kirsten Sach for the 2007 Ellerslie Flower Show that featured slim-line water tanks hidden in plaster walls, or as simple as the one she designed a year later for the Auckland Flower Show that comprised a downpipe running into a stepped system.

On top was a pond (complete with goldfish and aquatic plants), that overflowed into a box planted with wet and dry-tolerant plants that, when  conditions are right, overflows to a stony bed garden.

The garden won gold  and was created for $6000, including the shed the water ran off.

Kip described a rain garden as a “tier system” in that the water gradually moves through the planting and soil and gravel and is filtered along the way.

“They are great things,” he said, “because one day they’re flooded and the next day they’re dry. You need flora that can cope with that, but it’s an ideal opportunity to vary what you have in your back garden.”


Rain collection by Carl Pickens at the 2009 Ellerslie show. Photo: Sandra Simpson

Landscape designer Carl Pickens showed decorative rain collection in his award-winning 2009 Ellerslie International Flower Show garden. The small bowls acted like a chain in that water ran down the links and finally into the large bowl which then overflowed into the adjacent reed bed.

Further reading:

This article was originally published in the Bay of Plenty Times and appears here with permission. It has been updated slightly.

Slasher council takes on Tropical Display House

Startled to read in my local paper last week that our supposedly cash-strapped council is considering closing the Tropical Display House in Cliff Rd to save $100,000 a year. This is the same council that decided to stop mowing reserves so often to save money and then back-tracked when there was a public outcry.

Their rationale seems to be that because the visitor book isn’t signed very often, clearly it doesn’t have enough visitors to warrant keeping it open. Yep, these are the people running our fair city. I visit the display house regularly – it’s a good place for photos – and never sign the visitor book. It’s not compulsory and it’s hard to think of anything meaningful to say, apart from the banal and obvious.

The outcry that has followed is predictable and bewildering in about equal measure. The paper quoted Facebook comments, many of which were along the lines of “I’ve lived here 15/12/10 years and I never knew it was there”. The lack of curiosity people have about where they live never fails to astound me.

One councillor then thought it would be a good idea to do the contractor – Aztec Gardens (Liani Smith) – out of her job and let a “community group” run the place. Read more about that here. All I will say about that is, Cr Curach clearly has no idea how difficult it is for volunteer groups, any volunteer group, to attract enough members, especially members who are fit and able and who have expertise.

The council is also considering selling reserve land to a developer – low-lying land below a bluff, across from an estuary and right beside an expressway. It’s much more valuable as reserve and I would pity anyone who built a home there.

But this new set of councillors (elected last October) are either panicked or wanting to be seen as granite-jawed budgeters and are trying to trim and snip and slice at all sorts of things. True, toxic mould has unexpectedly been found in the council HQ, shifting staff all round town (and no doubt the council is having to pay jacked-up rents), but the building was due to be retro-fitted for earthquake strengthening anyway, and the councillors were aware of that, so some of the cost would be planned for, and have a contingency in it. And, let’s not forget, that the building has leaked before and after it was “refurbished” with an extra floor on top so it can’t have come as a huge surprise that the regular soakings have led to mould. It might be cheaper to demolish the whole thing and start again.

In 1999 the Robbins Rose Garden next door to the Tropical Display House was in a sorry state – uncared for with sparse plantings and the site under threat of being turned into a carpark by the council. Ten years later, thanks to the contacts and hard work of (now former) parks co-ordinator Ned Nicely and head gardener Megan Webber the garden was something of which the city could be proud.

The Tropical Display House is pretty good too.