A gardening tip I've been aware of for years, but have never implemented til now, ... when making a veg.garden bed, dig out to about 60cm deep, place old mattresses in the bottom, (foam type now), to retain moisture, and then add soil/manure/straw/hay, etc. I didn't have mattresses but placed thick cardboard and underfelt,(could also use carpet), which will hopefully do the same job. It will also deter tree roots from accessing your veggy garden so easily.
