There is plenty of talk about tree planting for cooling our cities. Over my last 40 years landscaping, I have been lucky to plant trees across NSW and the Middle East. In both these places water and the timing of its application has been a major factor in success. My team and I have used all sorts of techniques to improve survival rates and long term growth on projects like the M7, Hume Hwy, Western Sydney and Port Botany where we planted over 1 million trees. Here are some tips, especially about water holding capacity of the soil and its ability to grow some of the most important parts of a tree, the roots!
More recently I have been working with long term soil improvements in tough situations. Both I and Sydney Soil Laboratories (SESL) have some good news on soils performance with added mineral wool. Mineral wool is a natural material that’s safe to use and lasts a lifetime in supporting tree growth. I have carried out numerous experiments that show benefits for reduced watering requirements and better growth of plants.
This is what SESL said.
In SESLs opinion the Flocks product provides soil structure with significant reduced slumping over time in comparison to the lightweight media without Flocks (the Control). The Flocks also allows maintained air-filled porosity without significant reduction in oxygen levels. The addition of Flocks at a rate of 20- 30% to the lightweight media blend initially improves the water holding properties of the mineral based blend by around 9%. The water-holding capacity improves with time (5% improvement) as the media settles however not at the expense of the air-filled porosity. The Control showed higher WHC but this was at the expense of the AFP. The toxicity bioassay shows germination to be at an acceptable rate with the 30% contribution of Flocks however the growth rate isn’t as rapid as the 100% lightweight media. SESL recommends a full growth trial is undertaken to measure the effects of drought on non-irrigated blends.
For use when planting trees on concrete slab
