StryderNotavi

I've got a wattle that currently has a thinner than ideal trunk. I've been looking into what I can do to encourage it to develop a thicker trunk. Mostly this seems to be about only providing the minimum amount of support it needs and keeping it loose so that the wind / swaying stimulates trunk growth.

But in passing I've heard that trimming the lower branches can also help. So far this is just a rumour to me and I'd like to substantiate it somehow. Have others heard the same?

Also - with the heat we're getting lately do I need to worry about stressing out the tree? I probably don't need to remove that many branches (should be less than 10%). Is there a good guide for how much I can trim without stressing the tree?

I've been reading up on the various persistent herbicides that are out there and how they can pass through animals and composting intact and I was wondering how significant an issue this would be for those of us gardening in Australia.

For my fellow gardeners, I'd like to know whether you've encountered this issue in your gardens and what steps you take to reduce the risk of contaminated materials entering your garden?

I've got a young silver banksia that is getting a bit unruly and I'm looking for a useful guide for understanding how they respond to pruning. Ideally want to understand what they respond well to and how I can train them to grow to suit my garden.

I basically want to encourage it to grow upwards more, so that it can rise above a fence to gain better access to light and provide screening from neighbours. Also hoping that as it grows it'll create room for a bit of an understory in the same location.

Does anyone have any recommendations?