when to mow

ivy tree

I have a small newly laid lawn, its been down for 3 weeks and is looking good, it is also getting rather long and I'm wondering  when i should give it a light mow,

Borderline

If it is growing quite tall now, then yes, you can set the mower on the highest setting for the first cut. But don't rake the areas before or after cutting as the top layer is probably still quite fragile.