Tuesday, March 8, 2016

It's time for a new vision

This Claret Ash has died because the resident is about to demolish the house and has turned off the irrigation to the verge.

In this post I talked about how we can use temporary irrigation to tide trees over in this situation but, long term, is it really sustainable to rely on trees that rely on irrigation? A truly resilient urban forest is one that can survive on natural precipitation alone.

Here's how we can build it:
  • Residents give their verges back to the council
  • Only trees which can survive on natural rainfall are planted
  • Multiple trees are planted per verge so that the forest becomes self-mulching
  • No other planting on verges is allowed (takes moisture from the trees)
  • No irrigation of verges is allowed (makes the trees dependent)

Click photo for a better look

It would look something like this.

This then is the vision not of a forest in the city, but a city in the forest.

It's the vision the City of Melbourne has already articulated and is working towards.

I think we should too.


  1. I think it's fine for people to irrigate or water verges, particularly if they are also using them for edible gardens. Some of us are lucky (or sensible) enough to have private yards, but many will miss out. An edible / useful verge garden is something which can be shared with the street / community. Irrigating, maybe with grey water (ideally WSUD but that's another long story) can replenish the depleting groundwater. I am sick of people who say watering the soil is "wasting" it, meanwhile using flush toilets, buying plastic packaged lettuce leaves from Carabooda and living in denial. Water belongs in the soil. We should ensure it ends up in the soil, not being used as a vehicle to transport pollution. The living soil is one of the most vital ecosystems on the planet. A healthy urban forest relies on living soil. Trees can share resources with understorey plants and the nutrient cycle can be complete.

    1. You might be pretty limited as to what edible plants you can grow under trees. Also, irrigating anything under the trees will just make the trees dependent on the water again - the main thing we're trying to avoid.

    2. Trees ARE dependent on water- SOIL, the life that sustains trees, needs water. Most gardeners will confirm that trees will indeed "dominate" and extract water to the detriment of cover crops, not the other way around. The key is to have a symbiosis, a balance. Irrigation is not something to avoid, it is something to channel, design well, to make the best use of available resources. WSUD and rain gardens, grey water and stormwater harvesting are all irrigation methods currently rare in Perth - time to start. A successful urban forest strategy recognises the interconnected nature of these elements, and designs infrastructure to support life. As said above, sending water to the drain instead of soil is wasting it - we can do much better and green this city.

    3. Yep, no problem with WSUD and channelling storm water to trees - that's all part of "natural precipitation". I'm just suggesting we don't want an urban forest that relies on precipitation that people can turn off.

  2. Good idea Grayden and worthy of consideration. It'd be interesting to know what the take up would be. Concerns could be fire and the passive surveillance/visual interaction that planners like between the street and the house.

    1. G'day Chris
      Yes, both valid concerns. Fire can be addressed by not using too many Eucalypts and other combustible trees. Passive surveillance would be achieved by not having ridiculously close spacings (the example in the photo is admittedly a bit over the top) and no under-storey. Perth Street Tree would like to do a demonstration street of this technique (preferably a short one :)) so let me know if there's an interest in your neck of the woods. Regards, GP