I am putting in new raised beds for a vegetable garden. The beds will be 40cm (16 inches) high. The beds will line the length of a fence and I am planning to put a row of fruit trees (possibly blueberries and passionfruit) between the beds and the fence.
In order to try and prevent the tree roots from colonising the vegetable beds and stealing all the water and nutrients, I am planning on laying porous weed matting underneath the raised beds. My theory is that will keep the tree roots away from the vegetable soil but still allow drainage.
However, I have received strong advice from a family member that this isn't sufficient and that the trees will still suck the vegetable beds dry. Basically I've been told that you can't put fruit trees anywhere near vegetable beds if you want the vegetables to thrive.
Is this correct? Is there any way to make this work? If so I've considered some even more drastic measures such as hammering in sheet metal vertically down the back of the vegetable beds to keep the tree roots from growing in under the beds (they could happily grow the other way into the neighbours place as they don't have anything growing along that fence). Would this work?