yes root pruning increases the size of the root ball. When you cut a root it releases a hormone which stimulates root growth. The plant quickly replaces the roots you cut and over compensates creating more roots.

Why big roots, wouldn't having more surface area of root contact to soil be best.

big roots have very low surface area and the older roots dont do any absorbing
harris7 Reviewed by harris7 on . Root pruning Has anyone ever tried root pruning on there plants? Root pruning is essentially the same as normal pruning. You cut off roots. You do this because old roots which are very large do no take up anything. They are just like large branches at the top of the plant, they are pathways for nutes/water So you cut these large roots and whatever was attached just dies and the site of the cut grows lots and lots of new roots. This is done lots in gardening it increases root growth and creates Rating: 5