If trees are allowed to grow too closely together not only does this make access and maintenance difficult, it also discourages the full bearing potential of the tree from being attained as young nutlets frequently abscise when they find themselves in full shade.
A typical variety could expect to have a spread in feet roughly equivalent to its age in years. The Ministry of Agriculture leans towards a general recommendation of 30' on the square, which is quite generous. The absolute minimum might be considered to be 24' spacing, as in the photo below.
Take this table as a general guide.
|Spacing in Feet||24||28||30||35|
|Trees per Acre||76||56||48||36|
Trees at 24 foot spacing