Funny that isn't it!! and funny why corn always grows in straight lines in between these rows of bushes and some of these rows of bushes appear to have gaps with gates in!!
I think its best if we just humour him/her (probably her)
To devide fields bankings of earth and stones were placed around its edges, as these were not cultivated as per the field ,a normal build up of natural seeds found an ideal area to germinate on.
If the field is Not heavily grazed or cultiveted then bushes will eventually grow in the middle. In a few years trees will win the battle from grass competition and scrubland will form, this will be succeded by woodland.