An old science teacher of mine told me that for every equation there is always an exception. In horticulture, in my opinion, equations and theories can all be discarded. The ‘theory’ for grass seed to germinate for example is that it should take ten to fourteen days to germinate. But that is based on the fact that you have suitable growing medium [soil] ; temperature in this case at approximately twelve to fourteen degrees depending; water; air and sunlight – the five factors required for the growth of any plant. So how long will it take for seed to germinate? with conditions at almost twenty degrees and no rain? a long time.
Back to the roll out lawn! Now you have a germinated green seed carpet the bottom of which should be flat with some white fine root hairs slightly protruding at the base [look closely]. If soil preparations are done to perfection one should have what is in theory castor sugar like soil [a fine tilth to the horticulturist] with a roll of weighted grass on top. Until the rootzone develops [ie. the fine white hairs teeth into the fine soil and form a matting ie. bind together so as the grass cannot be pulled off the ground when you grab it] and also the soft ground beneath hardens enough to take your weight – then don’t walk on it. You will need to test the water, so to speak, to see if it’s alright. If the kids do dancing on it be warned that’s how you get potholes in your new lawn
This sounds a really long answer to a simple query – but what I am trying to do is give an understanding in a nutshell of a situation that has taken some years of education and experience to know by touch and sight.
enjoy the cutting, buy a mulching mower and be kinder to the environment.