• Cheaper than Redgum  
• Lighter and easier to handle    than Redgum  
• Sustainable plantation timber
  
• Impregnated with poisons to    preserve the timber

This is the method first devised to preserve pine and has long been criticised for it's use of arsenic as it's key preserving ingredient.  For details see the Wiki link http://en.wikipedia.org/wiki/Chromated_copper_arsenate

A newer method of treating pine that is claimed to be much more benign than the CCA process as it does not use arsenic.  It is however still a poison and should always be treated as such.  It is also very corrosive to metal.  For details see the Wiki link http://en.wikipedia.org/wiki/Alkaline_copper_quaternary

ACQ treated pine is becoming much more common but it pays to check with your timber supplier to make sure which method has been used.  I have been told that treated pine posts are more likely to be treated using the old CCA method while sawn treated pine is more likely to use the ACQ process.

It is my opinion treated pine, especially if it is processed with the ACQ process has been unfairly maligned and is much more environmentally friendly than many environmental groups make it out to be.  I do however recommend that if you are building vegetable beds out of treated pine you only use ACQ treated wood and that you line the inside of the bed with plastic weed matting.

This is a product that I have not tried myself but I do know people who have.  As Redgum and Jarrah becomes more expensive and scarce I believe plantation grown sugar gum will become the natural alternative for these timbers.

•  Simple to set up and easy to move
  
• Easy to knock out of position  
• Gaps between the bricks provide good cover for pests