Friday, February 19, 2016

TPZ's on building sites have to include water

Click photo to enlarge.

The council has tried to do the right thing here and protect it's street tree during construction of the new house.

It mulched the tree, put a temporary fence around it and stuck this sign up.

But they forgot one thing…

Cnr Oban / Chipping, CityBeach (click to enlarge)


In Perth, TPZ's (Tree Protection Zones) have to include temporary irrigation or they're pretty much a waste of time.

It's not hard - just some 19mm poly with bubblers* and a battery-operated controller will do it. Simple, cheap and effective.

What was ironic here was that a tradesman came out while I was taking the pictures. I thought I might be in for a punch up. Instead he said, "I know, it sucks doesn't it?"

* Keep the bubblers inside the compound so they don't get damaged. The compound actually needs to be bigger here so the bubblers can be placed around the tree's drip zone instead of it's trunk.


  1. Hi Grayden, a good point. Perhaps as part of the development approval a "tree bond" needs to be paid and then refunded at the end of the development if the tree is still healthy. Alternatively, just let the developer/builder know that a significant fee will be imposed if anything happens to the tree. i believe we need to start putting a price on trees -

    1. Hi Chris
      Thanks for that. Bonds are better than nothing but I always think if you have to actually call on them it's too late - ie the tree has been lost. Far better to not let the tree get damaged in the first place. And the key to that is really good TPZ set ups and regular monitoring of them to make sure they're not being violated.

    2. You sent your post to Cambridge Coastcare but I cannot find you on our membership list. If you want to join, there's a form on our website Street trees are a bit beyond our scope of activity but I share your concern over the tree at 65 Oban Rd - there are marks around the base of it which indicate that someone has hacked off the bark all the way round with an axe or hatchet. This was done some time before the council decided to put a protection zone around it. As a neighbour, I am surprised that we didn't hear the chopping being done but we didn't.

    3. The chopping around the base isn't sufficient to have killed the tree - it's definitely lack of water. The tree has grown up on irrigation and can't adapt to having it suddenly turned off. The sad thing is the verge will be be irrigated again once the house is finished and the tree would have been OK! This is why we need to have temporary irrigation inside TPZ's during house construction.