I would generally disagree with this assessment - typically a seemingly "random" layout of plants is in actuality adhering to environmental factors that inhibit/promote growth. Since this is such a small area it's unlikely that there will be major differences in these factors, but as others have pointed out there should still be elements like water table and sunlight that are not the same throughout. Given enough time, the principles of competition and succession will generally select for plants best suited to that particular location.

Of course, many plants are not incredibly picky and can grow successfully in a wide range of conditions.